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197 Cards in this Set
- Front
- Back
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What is a characteristic of both diabetes insipidus and diabetes mellitus?
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high urine output
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What causes neurogenic diabetes insipidus?
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SON and PVN neurons do not respond to the usual control signals and do not secrete enough ADH
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What causes nephrogenic diabetes insipidus?
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kidney cells do not respond to ADH
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What causes psychogenic diabetes insipidus?
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psychoneurotic disorder that results in compulsive water drinking
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If urine osmolality inc after 2hr water restriction, what type of diabetes insipidus is likely?
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psychogenic
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If urine osmolality doesn't change after a 2 hr water restriction, what type of diabetes insipidus is likely?
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nephrogenic or neurogenic (central)
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If pt has no response after injection with ADH, what type of diabetes insipidus is likely?
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nephrogenic
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If urine osmolality inc and plasma osmolality dec, what type of diabetes insipidus is likely?
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neurogenic (central)
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What can cause SIADH?
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some lung and brain malignant cells can secrete ADH
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What is seen with SIADH?
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water retention (hypervolemia) which causes hypertension; hyponatremia due to inhibition of aldosterone secretion and stimulation of ANP; "salt-wasting" condition
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What are the 2 thyroid hormones?
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T3 and T4
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What class do thyroid hormones belong to?
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tyrosine hormones; tyrosine synthesized in body, but iodine must be obtained from diet
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What is another name for T4?
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thyroxine
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What is another name for T3?
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triiodothyronine
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What regulates thyroid hormone secretion?
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every step controlled by TSH from anterior pituitary
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What is TSH controlled by?
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hypothalamic TRH
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When is T4 converted to T3?
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after release from thyroid
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Where are thyroid hormones stored?
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in the colloid in the follicles
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What is the first step in thyroid hormone synthesis?
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follicular cell synthesizes enzymes and thyroglobulin for colloid
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What is the second step in thyroid hormone synthesis?
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Iodine is co-transported into the cell with Na+ and transported into colloid
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What is the iodide trap?
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Na+-iodide symporter actively transports iodide against its gradient
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What is the third step in thyroid hormone synthesis?
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enzymes add iodine to thyroglobulin to make T3 and T4
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What enzyme oxidizes iodide ions so they are incorporated into tyrosine moieties of thyroglobulin?
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thyroid peroxidase
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What molecules are coupled to make T3 and T4?
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MITs and DITs
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What is the fourth step of thyroid hormone synthesis?
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thyroglobulin is taken back into the cell
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What is the fifth step of thyroid hormone synthesis?
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Thyroglobulin molecule fuses with lysosomes to separate T3 and T4 from the protein
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What parts of the thyroglobulin molecule are recycled?
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MIT, DIT, and AAs
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What stimulates every step in thyroid hormone synthesis?
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TSH
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How are thyroid hormones transported in the blood?
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bind reversibly with proteins, mostly TBG (thyroxine-binding globulin)
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What is the predominate form of thyroid hormones in the blood, bound or free?
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bound form is in equilibrium with free form; free form is the bioactive form
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How do T3 and T4 enter the cell? What happens next?
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enter cell by either diffusion or by carrier-mediated transport; binds to thyroid hormone receptor in nucleus of cell and activates thyroid response element
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Where and what converts T4 to T3?
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deiodination in liver and kidneys
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Which is more active, T3 or T4?
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T3 is 4 times more active due to its affinity for the receptor
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Some T4 can also be converted into what inactive molecule?
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inactive reverse T3
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rT3 levels inc during? What is its purpose?
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fasting or carb restricted diets; conserves energy since T3 stimulates metabolism
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Thyroid hormone in normal amounts has what effect on metabolism?
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anabolic
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Pathologically high amounts of thyroid hormone have what effect on metabolism?
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causes futile cycles of metabolism; net effect is catabolic
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Thyroid hormones are permissive for what other hormone's activity?
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GH
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What occurs in children with thyroid hormone deficiency?
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growth retardation (dwarfism)
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What hormone is essential for normal CNS development and fx?
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thyroid hormone
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What are thyroid hormones effect on the NS?
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enhances SNS activity (sympathomimetic effect)
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What are the two sympathomimetic effects of thyroid hormones?
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upregulates catecholamine receptors and inc the speed of nervous reflexes
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What is the cause of primary hypothyroidism?
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failure of thyroid gland that can be due to autoimmune inflammation
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What is the cause of secondary hypothyroidism?
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failure of pituitary to secrete TSH
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What is the cause of tertiary hypothyroidism?
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failure of the hypothalamus to secrete TRH
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What can lack of iodine in the diet cause?
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hypothyroidism
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What are the two main signs and symptoms of hypothyroidism?
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depressed NS activity and low metabolic rate
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What are some of the S/S seen with depressed NS activity?
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slow weak pulse, slow reflexes, SLOW SPEECH, lack of alertness, poor memory
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What are some of the S/S seen with low metabolic rate?
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intolerance of cold, elevated cholesterol, weight gain, fatigue, puffy doughy appearance
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What is myxedema?
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puffy, doughy appearance seen in pts with hypothyroidism; most obvious in face; due to accumulation of CT and proteins which absorb water
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What is the cause of primary hyperthyroidism?
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thyroid tumor that secretes excess thyroid hormones
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What are some other causes of hyperthyroidism besides a thyroid tumor?
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autoimmune disease (Graves disease or thyrotoxicosis) in which TSIg stimulates TSH receptors; excess secretion of TRH and TSH by hypothalamus or pituitary
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What are the three main S/S seen with hyperthyroidism?
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high metabolic rate, inc NS activity, bulging eyes
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What are some S/S of high metabolic rate?
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intolerance of heat, weight loss, muscle wasting and weakness
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What are some S/S of inc NS activity?
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high heart rate, palpitations, irritability, anxiety, inappropriate emotionality
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What is exophthalmos?
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bulging eyes seen in pts with Graves disease
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What is a goiter?
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enlarged thyroid gland; usually only seen in underdeveloped countries
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What hormone maintains the structural integrity of the thyroid gland?
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TSH
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How does excess TSH affect the thyroid gland?
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causes hypertrophy and hyperplasia of the follicular cells; goiter
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How does TSH deficieny affect the thyroid gland?
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causes atrophy of the gland
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What can cause a goiter in pts with hypothyroidism?
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lack of iodine in diet
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What can cause a goiter in pts with hyperthyroidism?
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excess secretion of TRH and/or TSH; pts with Graves disease
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What are the 3 hormones responsible for Ca++ homeostasis?
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PTH, Calcitonin, 1,25 Vit. D3
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What is Ca++ homeostasis essential for?
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bones and teeth, all cells, nerve and muscle fx, blood clotting
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What is the amount of total body Ca++? Where is most located?
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1 kg; bones and teeth
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What amount of Ca++ is found in the ECF?
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0.05% protein bound; 0.05% free ionized
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What form of Ca++ is bioactive?
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free ionized Ca++
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How is free ionized Ca++ in the ECF regulated?
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exchange between bone and ECF; renal excretion
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How is total body Ca++ regulated?
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GI absorption of Ca; renal excretion
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What stimulates PTH synthesis and secretion?
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low plasma ionized Ca++
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What does PTH do?
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raises free ionized Ca in ECF
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What type of feedback loop controls PTH release?
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negative
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Is the level of PTH hormone inc or dec when plasma Ca++ is elevated?
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dec
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Is the level of PTH hormone inc or dec when plasma Ca++ is low?
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inc
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What do the two G protein Ca++ receptors do?
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one is stimulatory and the other is inhibitory; both control a separate pathway
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What activates both G protein Ca++ receptors?
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high plasma Ca++
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What is the fx of Gs in response to elevated plasma Ca++?
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stimulates Ca++ release from internal stores
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What is the fx of Gi in response to elevated plasma Ca++?
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inhibits second messenger activation and cAMP dec
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What is the result of both Gs and Gi being activated in response to elevated plasma Ca++
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exocytosis is inhibited
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What happens to PTH release when plasma Ca++ is slightly elevated?
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some PTH is secreted
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What is the fx of osteoblasts?
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create new bone by secreting organic matrix-colloid-and then mineralizing it with calcium phosphate crystals
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What is the fx of osteoclasts?
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dissolve bone by solubilizing the crystals
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How does PTH affect bone?
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causes bone remodeling
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What does PTH stimulate?
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movement of ionized Ca++ and phosphate from bone to ECF; activates osteoclasts to dissolve bone
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PTH tips bone remodeling in favor of?
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resorption
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How does PTH affect renal absorption of Ca++?
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inc
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How does PTH affect renal excretion of phosphate?
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inc
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What hormone induces the activation of Vit.D?
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PTH
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What cells secrete calcitonin? Where are they located?
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C cells of the thyroid gland
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What are the two fxs of calcitonin?
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dec movement of ionized Ca++ from bone to ECF; inhibits activity of osteoclasts
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What is the bioactive form of Vit.D?
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1,25(OH)2
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What is calcitriol?
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another name for the active form of Vit.D
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Where does Vit.D come from?
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produced in skin by action of sunlight and found in some foods
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What is 7-dehydrocholesterol?
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biologically inactive precursor to Vit.D; found in the skin
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How is Vit.D activated?
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by the addition of 2 hydroxyl groups
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Where is the first -OH in Vit.D activation added? The second?
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liver; kidneys
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What 4 things stimulate the kidney hydroxylation enzyme?
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PTH, low plasma ionized Ca++, low plasma ionized phosphate, prolactin
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What happens in a breast-feeding woman if she is Vit.D deficient?
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she can lose Ca++ and P from her bones and teeth
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When plasma ionized Ca++ is high, what does renal hydroxylation produce?
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the inactive form of Vit.D
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What is the inactive form of Vit.D?
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24,25 (OH)2 Vit.D
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When plasma ionized Ca++ is low, renal hydoxylation produces?
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the active form of Vit.D
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What is effect of activated Vit.D?
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inc total body Ca++ by inc GI absorption of Ca++
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What is the second effect of activated Vit.D?
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inc ECF ionized Ca++ by enhancing response of bone to PTH; causes resorption; quick response
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When activated Vit.D inc GI absorption of Ca++, is the response slow or fast?
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slow long-lasting response due to gene activation; also a dose dependent response
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What causes hypoparathyroidism?
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rare autoimmune disease
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What happens to PTH secretion and plasma ionized Ca++ levels in hypoparathyroidism?
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PTH secretion is low which results in low plasma ionized Ca++
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The low Ca++ levels that occur with hypoparathyroidism cause?
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inc neuromuscular excitability with paresthesia and tetany
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What is the condition caused by PTH receptor defect?
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pseudohypoparathyroidism
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What causes the primary form of hyperparathyroidism?
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usually due to hypersecreting parathyroid tumor
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What happens to PTH secretion with primary hyperparathyroidism?
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high PTH results in hypercalcemia
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What is the cause of secondary hyperparathyroidism?
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chronic renal disease or Vit.D deficiency
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Is a patient with secondary hyperparathyroidism hypocalcemic or hypercalcemic?
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hypocalcemic which causes high PTH production
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What 3 things can occur in pts with hyperparathyroidism due to the high PTH level with elevated Ca++
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depressed muscle and nerve excitability, inc risk of fractures, risk of kidney stones
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What occurs in pts with a Vit.D deficiency?
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impaired GI absorption of Ca++
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What happens to PTH levels in pts with a Vit.D deficiency?
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they are inc and cause bone demineralization
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What is Rickets?
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bone demineralization in children due to Vit.D deficiency
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What is osteomalacia?
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bone demineralization in adults due to Vit.D deficiency
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What is the rule of thumb for Vit.D production in the skin?
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if your shadow is longer than your height, the sunlight is too weak to cause Vit.D production in you skin
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How does skin pigmentation affect Vit.D production?
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with inc amounts of pigmentation, the percent of Vit.D deficiency inc
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What are a few causes of Vit.D deficiency?
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wearing too much clothing, using too much sunblock, being outdoors too little
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Vit.D supplements lower the risk of premature death by what percent?
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7%
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What is osteoporosis?
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condition in which bone resorption is greater than bone formation
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What happens to the fx of osteoblasts and osteoclasts in pts with osteoporosis?
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reduced osteoblast activity and inc osteoclast activity
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What happens to plasma levels of Ca++, phosphate, PTH, and Vit.D in pts with osteoporosis?
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usually normal
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Does bone mass dec with aging?
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yes
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What role does estrogen play in bone resorption?
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inhibits bone resorption by dec osteoclast activity and inc osteoblast activity
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Why is the incidence of osteoporosis inc in post-menopausal women?
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because their estrogen levels are dec
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What are some ways to prevent osteoporosis?
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getting adequate Ca++ and Vit.D throughout life, doing weight-bearing exercises, not smoking
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What % of the pancreas is exocrine?
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98%
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What % of the pancreas is endocrine?
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2%
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What is secreted from the exocrine part of the pancreas?
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digestive enzymes and bicarbonate
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What are the exocrine secretions released through?
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pancreatic duct
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What is secreted in the endocrine portion of the pancreas?
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peptide hormones regulating glucose and other intermediary metabolism
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How are the endocrine pancreas secretions released?
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exocytosis; drains into hepatic portal vein
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What are the structural and functional units of the endocrine pancreas?
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islets of Langerhans
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What do beta cells of the pancreas release?
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insulin and amylin
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What do alpha cells of the pancreas secrete?
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glucagon
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What do delta cells of the pancreas secrete?
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somatostatin
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What do F cells of the pancreas secrete?
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pancreatic polypeptide
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What is the role of insulin?
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stimulates uptake and storage of energy substrates
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What is the role of amylin?
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moderates insulin's actions
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What is the role of glucagon?
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stimulates production of glucose by liver
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What is the role of somatostatin in relationship to the pancreas?
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general inhibition of exocrine and endocrine pancreatic secretions; acts in a paracrine fashion
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What is the role of pancreatic polypeptide?
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inhibition of exocrine pancreatic secretion
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What is the fed state?
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during eating and the first two hrs after eating
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What is the fasting state?
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between meals
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What hormone from the pancreas dominates in the fed state?
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insulin
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What is the role of insulin in the fed state?
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cellular uptake of nutrients, carb and fat storage, protein anabolism
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What hormone from the pancreas is dominant in the fasted state?
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glucagon
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What is the role of glucagon in the fasting state?
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catabolism...breakdown of carb, fat, and protein stores
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What controls insulin and glucagon secretion?
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blood glucose concentration
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Will insulin or glucagon be released during high blood glucose levels?
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insulin
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Will insulin or glucagon be released during low blood glucose levels?
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glucagon
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Which glucose transporter allows rapid diffusion of glucose into beta cells?
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GLUT 2
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What determines the rate of glucose metabolism in the beta cell?
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glucose level in the blood
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What enzyme initiates the first step in glycolysis?
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glucokinase; generates ATP
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What does the ATP formed during glycolysis do in the cell?
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closes K+ channels and cell depolarizes; Ca++ channel opens and Ca++ levels rise which causes insulin granules to be exocytosed
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Is the GLUT 2 transporter insulin-independent or dependent?
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independent
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What does high blood AA level do to insulin secretion?
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increase
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What does entry of glucose into the SI initiate?
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GIP and GLP-1; feed-forward mechanism for insulin release
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What does inc parasympathetic activity do to insulin secretion?
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increase
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What does somatostatin do to insulin release?
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inhibits
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What does increased sympathetic stimulation do to insulin release?
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inhibits
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What does increased sympathetic stimulation do to glucagon secretion?
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increase
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What do high levels of AAs in the blood do to glucagon secretion? What is the purpose of this?
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increase; counteracts insulin's effects and prevents hypoglycemia after high protein and low carb intake
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Where are GLUT 4 receptors found?
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muscle and fat cells
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What type of receptor does insulin bind to? What happens once receptor binds?
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tyrosine kinase receptor; receptor phosphorylates insulin-receptor substrates (IRS) and second messenger pathways alter protein synthesis and exiting proteins
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What is the effect of insulin on resting skeletal muscle and adipocytes?
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signals the cell to insert GLUT 4 transporters into the membrane which then allow glucose to enter the cell
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In the absence of insulin can glucose enter resting skeletal muscle and adipocytes?
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No
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Does exercising muscle require insulin for glucose uptake?
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No
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Does resting muscle require insulin for glucose uptake?
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Yes
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Why is exercise important for patients with NIDDM?
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only way for them to decrease their blood glucose level (because of inc in the number of GLUT 4 receptors during exercise)
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What does a chronically high insulin level do to receptors?
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downregulates; due to obesity or acromegaly
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What effect does a chronically high insulin level have on receptors?
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downregulates
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What effect do excess glucocorticoids have on the affinity of insulin receptors?
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decreases affinity
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What upregulates insulin receptors?
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starvation
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What happens to the affinity of insulin receptors in pts with chronically low insulin levels or adrenal insufficiency?
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increases affinity
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What is the major effect of insulin on carb metabolism?
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dec blood glucose levels and increase carb storage; inc glycogenolysis in skeletal muscle and liver and dec hepatic gluconeogenesis
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What is the overall effect of insulin on fat metabolism?
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dec blood FA levels and inc TG storage; inhibition of lipolysis
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What is the overall effect of insulin on protein metabolism?
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dec blood AA levels and inc protein synthesis
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What are the effects of glucagon on fat and carb metabolism?
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inc blood glucose by inc liver gluconeogenesis and glycogenolysis; inc blood FA levels and ketone bodies; dec TG synthesis
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What can cause hypersecretion of glucagon? What would this hypersecretion cause?
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alpha cell tumor - glucagonoma; hyperglycemia
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What can cause hypersecretion of insulin? What would this hypersecretion cause?
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beta cell tumor - insulinoma; overdosage of insulin in diabetics; hypoglycemia
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What are the CNS effects of hypoglycemia?
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sweating, pallor, inc HR, anxiety, confusion, convulsions, coma
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What two things can cause DM and hyperglycemia?
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under-secretion of insulin or resistance to insulin
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When chronically high blood glucose damages blood vessels, what conditions can result?
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neuropathy, nephropathy, cardiovascular disease, blindness
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Are most diabetics Type I or II?
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Type II
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You can dx DM is fasting glucose is?
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>126 mg/dL
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You can dx DM if glucose level is ____ after 2 hrs oral glucose?
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>200mg/dL
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What is the etiology of Type I DM?
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autoimmune destruction of beta cells; usually develops in children
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What is the tx for Type I DM?
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insulin injections, dietary control, exercise
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What is Type II DM characterized by?
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impaired insulin secretion and resistance of target cells to its effects
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What does chronic over-eating do to blood glucose levels and insulin secretion?
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increases both
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Type II DM can often be associated with what 2 other diseases to be termed a "metabolic disease?"
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hypertension and hyperlipidemia
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What is the tx for Type II DM?
|
dietary restriction, weight loss, exercise, and oral drugs that stimulate beta cells
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What can chronically high insulin secretion do to beta cells?
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can cause beta cell exhaustion and then insulin injections are needed
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Is ketogenesis seen in untx Type I or II diabetics?
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Type I
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