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92 Cards in this Set
- Front
- Back
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What are the chemical names for the thyroid hormones T3 and T4?
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T3: Triidothyronine
T4: Tyroxine |
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Very briefly describe the structure of the thyroid follicles.
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central luminal regions filled with a protein-containing material known as colloid, surrounded by a layer of follicular epithelial cells.
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What is the limiting step of hormone synthesis in normal thyroid?
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Iodide uptake by the follicular cells
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What enzyme is involved in the iodine pump mechanism?
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Ouabain: sensitive Na/K ATPase
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What is the approximate normal thyroid to serum iodide ration?
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Thyroid concentrates iodide to levels 25 times that of the serum
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What are the effects of CIO4 and SCN?
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CIO4- an ion with similar partial specific volume that can inhibit the pump
SCN- a competitive inhibitor of transport that are not stored |
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What is iodinated by the reaction involving hydrogen peroxide, iodide ion, and thyroid peroxidase?
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Iodination of tyrosyl residues on thyroglobulin
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What is the function of thyroglobulin?
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Thyroglobulin serves as a storage form T3 and T4.
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Where is thyroglobulin stored, and where is it degraded
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stored: in lumen of follicles as colloid
degrades: in vesicles called phagolysosomes. in follicle cells |
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What happens to most of the T4 (3,5,3',5'-tetraiodothyronine) in the target tissues?
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3,5,3',5'-tetraiodothyronine is deiodinated by the enzyme 5’ deiodinase to yield T3.
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What is reverse T3?
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Reverse T3 is an inactive form sometimes formed.
Usually in largest amounts in chronic diseases, starvation, and in the fetus. |
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What are the general effects of thyroid hormones?
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anabolic in most tissue
slow onset and long lasting inc. production of: RNA and DNA epidermal growth factor increase HGH synthesis |
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Goiter
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Enlargement of the thyroid gland.
Caused by iodine deficiency. T4 and T3 levels are low causing elevated TSH levels leading to enlarged thyroid |
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Graves
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hyperactivity of thyroid due to thyroid-stimulating antibody that binds to the TSH receptor activating it.
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Cretinism
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neonatal thyroid hormone deficiency
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Myxedema
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adult hypothyroidism
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By what mechanism do antithyroid drugs function?
What is 131I used for? |
They inhibit organification of iodine.
radioactive iodine treatment of hyperthyroidism |
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How many layers does the cornea have?
What are they? |
5 layers
Epithelium Basal lamina Stroma Descement’s membrane Endothelium. |
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Where does oxygen come from to enter the corneal epithelium
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From the pre-ocular tear film
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What vitamin deficiency leads to night blindness & corneal erosion?
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vitamin A
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What 3 processes does retinol control?
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1. Keratin expression in epithelium
2. Synthesis of glycoconjugates 3. Activates & induces creatine kinase |
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Which corneal layer controls dehydration & transparency by pumping ions out to the aqueous humor
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Corneal endothelium
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What % of the thickness of the cornea is stroma?
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90%
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Substrate and Enzyme to synthesize sorbitol and galacticol?
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sorbitol: glucose
galacticol: galactose ENZ: aldol reductase |
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What health problem can arise due to sorbitol or galacticol accumulation?
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Osmotic disruption (affects the layers of the cornea)
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Metabolize Sorbitol??
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Sub: Sorbitol + NAD
ENZ: Iditol dehydrogenase Prod: Fructose + NADH + H then fructose goes into glycolysis |
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Metabolize Galacticol??
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cannot use Iditol Dehydrogenase.
accumulates in the lens and cornea causing osmotic disruption |
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what is the functions for MiRNA?
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-suppress translation
-sometimes actives translation |
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what part of gene codes for MiRNA?
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-Introns
-few extrons |
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where does MiRNA bind?
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It binds to 3‘UTR of the mRNA and suppresses translations also binds coding region
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what is the role of MiRNA during development?
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specialization
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what is the use of MiRNA in medicine?
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therapeutic:
cancer and macular degen. |
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composition/function of synovial fluid
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lubricant around joints
interstitial fluid (not secreted) composed of: proteins, glucose, electrolytes, phospholipids and cholesterol |
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How does synovial fluid change in a specific pathological case?
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becomes cloudy
proteins increase leukocytes increase globulin decrease albumin decrease Fibrinogen then cause clotting |
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properties/function of aqueous humor
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maintain IOP
nourish cornea, lens, iris and acts as a lens properties: protein conc. low ascorbate concentration higher than plasma |
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properties/function of vitreous humor
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maintains IOP
shock absorber acts as lens source of metabolite for retina 98% water and 1% colloid |
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properties/function of tears
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lubrication and oxygenation
breakdown bacterial wall lactoferrin reduce bacterial growth lysozymes, albumin, Ig...etc |
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Eccrine and Apocrine sweat glands
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Eccrine: soles of feet, palms head
dilute NaCl solution (lactate and urea) Aprocine: near hair follicles (pubis and axilla) viscous sweat and pheromones) |
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Pathologies involving sweat
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cystic fibrosis: NaCl very high causing odor and most common lethal genetic disease in white people
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role of vitamin A (retinol) in vision
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structural component of the visual pigment...Rhodopsin
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where vitamin A (retinol) stored?
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in the liver
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how is vitamin A transported
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trans-retinol is released from liver
transported by plasma retinol binding protein in retina, trans-retinol converted to trans-retinal (ox) becomes 11-cis-retinal |
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How is it possible that rhodopsins have such different absorbances while possessing the same chromophore?
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small variations in the AA seq of opsins allow for absorption in diff wavelengths of light
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role of cGMP and Na+ in photoreceptor function
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cGMP holds open Na+ channel
free flow of Na+ into outer segment triggers inc. release of glutamate |
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How does transmitter release vary with incident light (in the photoreceptor)?
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Dim light causes small and brief hyperpolarization that particularly turn off glutamate release. Brighter lights elicit larger and longer hyperpolarizations that more completely shut down the glutamate release.
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what is transducin
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G-protein and heterotrimer that bind to GTP/GDP
mediate effect of outside stimulus on cell met. |
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Name a few androgens.
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Testosterone
Dihyrotestosterone DHEA |
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Name a few estrogens.
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17-β estradiol
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Name the hormone that is required for embryo implantation.
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Progesterone
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What are the functions of DHEA?
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Weak androgen that is converted to a more potent androgen outside the adrenal gland.
It is a precursor for estrogen in postmenopausal women. Inhibits glucose –6-phosphate dehydrogenase regulates NAD+ coenzymes. |
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What are the functions of aldosterone?
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excretion of K+ and retention of Na+
raise blood pressure (high stress) |
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What are the functions of cortisol?
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stimulates:
gluconeogenesis (in liver) proteolysis (protein degradation) mobilization of FA increase blood glucose. |
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Which is the rate-limiting step in steroid biosynthesis?
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Occurs in mitochondrial matrix
RLS: Side chain cleavage of cholesterol into pregnenolone and isocaproaldehyde Pregnolone is the product |
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role of 5'reductase
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located in ER
converts testosterone into more potent androgen (dihydrotestosterone) |
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Name the enzyme that converts testosterone into estradiol.
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Aromatase (a type of P-450)
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Name the organ in which aldosterone produced
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zona glomerulosa of adrenal gland
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Name the organ in which cortisol are produced.
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zona fasciculate and zona reticularis of adrenal glands.
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Name the most common enzyme in steroid biosynthesis (generic name is sufficient).
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Cytochrome p450 hydroxylase (desmolase)
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Conversion of cholesterol into pregnenolone occurs in....
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mitochrondria
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Name the organ in which aldosterone produced
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zona glomerulosa of adrenal gland
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Name the organ in which cortisol are produced.
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zona fasciculate and zona reticularis of adrenal glands.
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Name the most common enzyme in steroid biosynthesis (generic name is sufficient).
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Cytochrome p450 hydroxylase (desmolase)
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Conversion of cholesterol into pregnenolone occurs in....
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mitochrondria
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Name three types of bone cells.
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Osteoblast
Osteoclast Osteocytes |
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Which bone cell adds calcium to bones, and which degrades bone removing calcium?
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Osteoblast adds Ca
Osteoclast degrades Ca |
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What is the mechanism by which bone is cut by these cells?
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Osteoclasts start as stem cells in the bone marrow.
Then are released in blood stream as monocytes Form multinucleated osteoclasts that cling to bond surface Use collagenase, other enzymes and acids secreted at their ruffled borders to tunnel thru mineralized bone forming cavities that are invaded by other cells. Capillary sprouts off a nearby blood vessel Grows into a tunnel and osteoblasts line its walls making new layers of bone |
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Name the three major hormones involved in calcium homeostasis.
Which are peptides |
*Parathyroid hormone (PTH)
*Calcitonin Calcitrol |
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where is parathyroid hormones synthesized
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chief cells of the parathyroid gland.
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where is Calcitrol synthesized
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hydroxylated in the liver but completely modified in the kidney. Also able to be carried out in the placenta.
Product of Vitamin D (Cholecalciferol) |
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where is Calcitronin synthesized
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secreted by the parafollicular C cells of the thyroid gland.
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parathyroid hormone function
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acts to increase circulating levels of Ca., preventing hypocalcemia.
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calcitrol function
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increases the transfer of Ca and Phosphate ions across the intestinal mucosa
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calcitonin function
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acts as a PTH antagonist, reducing serum calcium levels, preventing hypercalcemia.
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Vasopressin and Oxytocin:
where synthesized secreted by |
Synthesized in the hypothalamus
Secreted by the posterior pituitary gland |
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Growth Hormone an Prolactin:
where synthesized secreted by |
Synthesized by the anterior pituitary.
Secreted by the anterior pituitary. |
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function of Vasopressin
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Inhibit water diuresis.
Causes water reabsorption in the distal renal tubule. Increases arterial blood pressure. |
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function of Oxytocin
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stimulate uterine contractions and is secreted during parturition. Also for breast feeding.
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function of growth hormone
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Affects metabolic processes in all parts of the body.
Stimulates growth in children by increasing amino acid transport into muscle and increases protein synthesis. Stimulates growth in bones. |
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function of Prolactin
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Stimulates lactation in the mammary gland.
Can also stimulate protein synthesis. |
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Briefly compare the structures of vasopressin and oxytocin.
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Both posterior pituitary hormones that differ by 2 amino acids.
Both nonapeptides with intramolecular disulfide bonds. |
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Disease: Laron Dwarfs
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deficient receptor in the liver.
Low levels of insulin growth factor (IGF) excessive levels of growth hormone |
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Disease: Growth Hormone Deficiency
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Dwarfs form insufficient amounts of GH in the infant.
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Disease: Pigmies
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Low levels of IGF
normal GH post-GH receptor defect. |
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Disease: Acromegaly
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excessive GH secretion after closure of the epiphyseal plate.
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Disease: Gigantism
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GH is secreted in excess before closure of the epiphyseal plate.
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Disease: Cushing's Syndrome
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excessive production of ACTH by the pituitary or by a tumor
hyperpigmentation from the release of MSH Excessive production of adrenal steroids produces sodium retention, resulting in hypertension or edema |
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What are endorphins?
Where are they synthesized and secreted? |
A family of compounds that bind to the same
CNS receptors as morphine and play a part in pain reception.
the anterior pituitary. |
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Disease: Acromegaly
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excessive GH secretion after closure of the epiphyseal plate.
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Disease: Gigantism
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GH is secreted in excess before closure of the epiphyseal plate.
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Disease: Cushing's Syndrome
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excessive production of ACTH by the pituitary or by a tumor
hyperpigmentation from the release of MSH Excessive production of adrenal steroids produces sodium retention, resulting in hypertension or edema |
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What are endorphins?
Where are they synthesized and secreted? |
A family of compounds that bind to the same
CNS receptors as morphine and play a part in pain reception.
the anterior pituitary. |
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To what proteins are T3 and T4 bound while in the circulation?
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thyroxin binding globulin
thyroxin binding prealbumin transthyretin albumin |
