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85 Cards in this Set

  • Front
  • Back
The thyroid gland is located ________ and __________ to the trachea, just below the thyroid cartilage (Adam's apple).
anterior, lateral
The thyroid consists of 2 lobes (one on each side of the trachea). The lobes are connected by a bridge of thyroid tissue called the ________, which is located just below the _________ __________, midway between the apex of the thyroid cartilage and the suprasternal notch.
isthmus, cricoid cartilage
The superior thyroid artery arises from the __________________________, whereas the inferior thyroid artery arises from the ____________ _________of the subclavian artery.
common or external carotid artery, thyrocervical trunk
Venous drainage is via multiple surface veins coalescing into superior, lateral, & inferior __________.
thyroid veins
forms of hypothyroidism characterized by thyroid enlargement (e.g. - ________- ___________ hypothyroidism).
iodine deficient
On microscopic examination, the thyroid gland is found to consist of a series of ________ _________ of varying size.
thyroid follicles
The thyroid follicles contain a material called the ________ and are surrounded by a single layer of cuboidal epithelium (_________ _________).
colloid, follicular cells
The colloid (thyroid follicles contain this material) contains large numbers of ______________ ____________.
thyroglobulin molecules; TGB
Each thyroid follicle is surrounded by a dense _______ network as well as individual cells called ____________.
capillary, parafollicular (C) cells
Thyroid hormones are a derivative of what amino acid
The two types of thyroid hormones __________ (T3) and ______ (T4).
triiodothronine, thyroxine
A majority of the thyroid hormone secreted by the thyroid gland is ___ (approx. ____%).
T4, 95%
Most of the ___ released by the thyroid gland is ___, however, is converted to ____ by target tissues
T4, T3
___ is about 4-5 times more potent than __.
T3, T4
Thyroid hormones are unique in that they contain ______% of the trace element _____.
60-65%, iodine
_________ are the only substances in the body that have iodine in their structure
thyroid hormones
hypothalamus > ____ > pituitary > _______ > thryoid
thryoid synthesis in _________ requires two things: _________ and ________.
colloid, iodine, thryoglobulin molecule
__________ cells produce T4 and T3.
What produces calcitonin
parafollicular cells (C cells)
Iodine is added to ________: one iodine, ____, two iodines, ____. MIT and DIT are hooked together. DIT+DIT=T4, MIT+DIT=T3.
tyrosine, MIT, DIT
Colloid can store a lot of thyroid hormone, enough to last _________.
8-12 weeks
The thionamides, methimazole (Tapazole) and propylthiouracil (PTU), are the primary drugs used to treat ____________.
MIT and DIT are called:
Antithyroid drugs inhibit ___________ __________and hence decrease the synthesis of thyroid hormone by inhibiting the oxidation of _______, the iodination of _______, and the coupling of iodotyrosines (MIT, DIT).
thyroid peroxidase, iodine, tyrosine
TSH Actions: 4 things
-stimulates iodide pump activity
-activates thyroid peroxidase
-stimulates TGB synthesis
-stimulates growth of thyroid follicles
-thyroglobulin (TGB) molecules
-thyroxine-binding globulin (TBG)
There are three major thyroid hormone transport proteins:

The total amount of thyroid hormones bound to these plasma proteins provides a substantial reservoir of T3 and T4.
-thyroxine-binding globulin (TBG)
-thyroxine-binding prealbumin (TBPA) or transthyretin
Thyroid hormones are transported in blood bound to ___________. Although only ____% of T3 and T4 are "free", it is the free fraction that is responsible for hormonal activity.
carrier proteins, 0.04%
It is also important to emphasize that thyroid hormones act as _______rather than as all-or-none signals that turn processes on or off. Much of what thyroid hormone does is ________, serving to facilitate the actions of other hormones and pathways. Thus, it is easy to forget the role of thyroid hormones in making other hormones (e.g. -- GH, epinephrine, etc.) ________.
modulators, permissive, work optimally
Attainment of normal adult stature requires optimal amounts of thyroid hormone.

There is no evidence that T3 or T4 acts directly on cartilage or bone cells to signal increased bone formation -- rather, thyroid hormones appear to act permissively or synergistically with _________ and _______________ to promote bone formation.
growth hormone, insulin like growth factors
The thyroid gland develops very early (_____days after conception); it starts concentrating iodide by about the 11th week of gestation; it begins secreting significant amounts of T3 and T4 around the ________week of gestation.
At the ________week of gestation, T3 and T4 have significant impacts on brain development -- some of the actions of thyroid hormones include growth of the cerebrum, vascularization of the cerebrum, growth of the cerebellum and neuron myelination -- while this thyroid hormone dependent development begins in utero, it is not completed until ____________ of age.
24 days, 18 - 20th, 18-20th, 2 to 3 years
____________ is one of the preventable causes of mental retardation -- major complications can be prevented if diagnosed early and started on replacement therapy; early diagnosis is difficult because the clinical signs are not apparent at birth and appear gradually; thus it is very important to screen newborns for ________________ and it is a routine newborn screening test in most of the developed countries
Specimens are obtained by heel stick filter-paper blood spot -- the results are more reliable if TSH test is done on day 5 of life and __ test between day 2 and 5 of life; there is a physiologic increase in ___ levels at 2-5 days of life, which is not seen, in hypothyroid infants
Congenital hypothyroidism, Congenital hypothyroidism, T4, T4
Increased secretion of thyroid hormones exaggerates many of the responses regulated by __________.

Some evidence suggests that thyroid hormones may increase the number of receptors for __________ and ________(beta-adrenergic receptors) in myocardium and other tissues.
SNS,epi, norepi
________________ -- a measure of oxygen consumption under defined resting conditions -- is highly sensitive to _______ hormone levels.
Oxygen consumption in all tissues except _____, ______, and _______ has been experimentally shown to increase in response to ______ hormones.
Oxygen consumption ultimately reflects activity of mitochondria and is coupled with formation of high-energy bonds in ATP -- splitting of ATP energizes cellular processes and ultimately results in heat production.
basal metabolic rate, thyroid, brain, testes, spleen, thyroid
Thyroid hormones stimulate carbohydrate utilization in most tissues, glycogenolysis & gluconeogenesis in ________, and glucose absorption from the digestive tract.
Thyroid hormones stimulate ________ and __________ of free fatty acids by cells.
lipolysis, beta-oxidation
Thyroid hormones increase the abundance of ______________ receptors in hepatocyte membranes -- this effectively lowers the amount of ____ in the plasma.
Thyroid hormones help to maintain the secretion of _________ from the kidneys and hence _________.
erythropoietin, erythropoiesis
Thyroid hormones ________ intestinal motility
The principal signs and symptoms of ____________ are related to increased heat production (e.g. – heat intolerance, sweating) ________ sensitivity (e.g. -- tachycardia, tremor) and other effects of thyroid hormones.
hyperthyroidism, adrenergic
Exophthalmos occurs with ___________ and is a result of ____________.
Grave's Disease, hyperthyroidism
examples of hyperthyroidism
-Graves' Disease (Diffuse Toxic Goiter)
-Toxic Multinodular Goiter (Plummer's Disease) / Toxic Adenoma
-TSH-Mediated Hyperthyroidism
-Subacute Thyroiditis
-Exogenous and Ectopic Hyperthyroidism
_______________ is second only to diabetes mellitus as the most common endocrine disorder in the US, and its prevalence is estimated around __ per 1000 individuals.
hypothyroidism, 18
________________ is caused by TSH deficiency,
secondary hypothyroidism
_________________ is caused by TRH deficiency.
tertiary hypothyroidism
causes of primary hypothyroidism
Chronic Autoimmune (Hashimoto's) Thyroiditis
Radioiodine Therapy
External Neck Irradiation
Iodine Deficiency or Excess
Congenital Thyroid Agenesis, Dysgenesis or Defects in Thyroid Hormone Synthesis
congenital hypothyroidism, also called:

Affects approx. 1 of every ___ births. Potential causes:

Neonatal screening & thyroid hormone replacement therapy averts permanent disabilities
-lack of thyroid gland
-abnormal biosynthesis of T3 & T4
-abnormal biosynthesis or secretion of TSH
Clinical Manifestations of Hypothyroidism: Many of the symptoms and signs that accompany the _____________________ are similar to those of hypothyroidism. As examples, older patients who are euthyroid may complain of fatigue, cold extremities, dry skin, and constipation.
normal aging process
Calcium (Ca+2) is important for a wide range of intracellular & extracellular biological processes including:
-muscle contraction
-blood clotting
-formation of cardiac action potentials
-enzyme activation
-cell signaling (as in second messenger systems like IP3)
-bone & tooth structure
Total serum concentration of calcium in human is maintained between _________ mg/dL. Deviations in either direction are not readily tolerated and, if severe, can be life-threatening
8.5 to 10.5 mg/dL
About _____ mg of Ca+2 is ingested per day, but only ___ of this amount is absorbed from the small intestine and enters the ECF.
1000, 1/3
Ca+2 is taken up along the entire length of the small intestine, but uptake is greatest in the _____ and ____.
ileum and jejunum
Both ionized and complexed calcium pass freely through the glomerular membranes. Normally, ______% of the 10,000 mg of Ca+2 filtered by the glomeruli each day is reabsorbed by the ____________.
98-99%, renal tubules
The adult human body contains approximately _____ g of Ca+2, about ___% of which is sequestered in bone, primarily in the form of ___________ crystals. In addition to providing structural support, bone serves as an enormous _________ for Ca+2 salts.
1000g, 99%, hydroxyapatite, reservoir
Each day, about ___ mg of Ca+2 is exchanged between ____ and the ___. Much of this exchange reflects resorption and reformation of bone as the skeleton undergoes constant remodeling.
600mg, bone and ECF
What are the three definable fractions of Ca+2 in the blood
1) ionized or “free” calcium 50%)
2) protein-bound calcium (40%)
3) complexed to citrate & phosphate forming soluble complexes (10%)
Both complexed and ionized Ca+2 are ultrafilterable, so that about 60% of the total Ca+2 in blood crosses semi-permeable membranes. Nearly 90% of the protein-bound Ca+2 is bound to ______ and the remainder to globulins. The binding of Ca+2 to albumin is __ dependent.
albumin, pH
Because it is the ionized fraction of Ca+2 that is physiologically important, it is not surprising that patients who hyperventilate and develop acute respiratory ______ may develop carpal spasm and even seizures due to increased neural excitability.
The binding of Ca+2 to albumin is __ dependent. Acute acidosis ________ (decreases or increases) binding and (decreases or increases) ionized Ca+2, whereas acute alkalois ________ binding with a consequent _________ in ionized Ca+2.
pH, acidosis decreases binding and increases ionized Ca+2, alkalosis increase binding and decreases ionized Ca+2
Parathyroid glands are well vascularized and derive their blood supply mainly from the _____________ arteries.
inferior thyroid
They are well vascularized and derive their blood supply mainly from the inferior thyroid arteries. These glands adhere to the posterior surface of the thyroid gland or occasionally are embedded with the thyroid tissue.
What are the most predominant cells in the parathyroid glands?
The principal or chief cells
What the two main functions of the principal or chief cells of the parathyroid gland?
a) synthesis & secretion of PTH
b) sensors of minute fluctuations of ECF Ca+2.
The function of the second parathyroid cell type, the _______ cells, is unknown. Some recent evidence suggests that they may be degenerated principal cells. Few ______cells are seen before puberty, but their number increases thereafter with age.
oxyphil, oxyphil
stimulus for secretion is hypocalcemia
-“straight-chain” protein hormone of 84 amino acids
-½ life in the blood of 2-3 minutes
-metabolized by its target tissues
-metabolites excreted in urine
What are the 3 tissues the parathyroid works on either directly or indirectly
bones (direct), kidney (direct), intestine (indirect)
PTH effects on bone (direct)
-stimulates existing osteoclast activity
-stimulates new osteoclast production
PTH effects on the kidneys (direct)
-stimulates the reabsorption of Ca+2 in distal convoluted tubules
-stimulates 1-hydroxylation of 25-hydroxycholecalciferol (i.e. -- activation of Vitamin D)
PTH effects on the intestines (indirect)
-intestinal uptake of Ca+2 is stimulated by "active" Vitamin D
-PTH has no directs effect on intestinal absorption of Ca+2
PTH stimulates 1-Hydroxylation of 25- hydroxycholecalciferol in the ______ (an organ) -- this creates the active form of _______ called 1(a),25 dihydroxycholecalciferol
kidney, Vit D
The protein hormone (32-amino acids) that is synthesized and secreted by the parafollicular cells of the thyroid gland.
calcitonin is secreted by what cells of the thyroid gland
Stimulus for calcitonin secretion in many animals is ____________.
Calcitonin will promptly and dramatically lower the level of ECF Ca+2 by acting on the _____ and _______.
bone and kidneys
Calcitonin does not appear to be a major factor in calcium homeostasis in humans. Recent evidence has shown that the importance of calcitonin may be limited to protection against excessive bone ________.
Possible etiologies for hypercalcemia:
-bone malignancies
-prolonged immobilization
-excess vitamin D and calcium in the diet
An ________ in ECF calcium depresses central and peripheral neural excitability, resulting in mental sluggishness, dulling of consciousness, muscle weakness and hypo-reflexia.
Increased concentrations of ________ in blood may cause _______ salts to precipitate out of solution because of their low solubility at physiological pH. "Stones" form, especially in the kidney, where they product severe painful damage (renal colic), which can lead renal failure and hypertension.
If the _________ is due to excessive bone resorption, an increased incidence of fractures can also occur.
calcium, calcium, hypercalcemia
Possible etiologies of hypocalcemia:
-surgical removal of parathyroids
-vitamin D deficiency
-impaired ability to activate vitamin D
When the ECF concentration of _______ (falls or rises) below normal, the nervous system becomes progressively more excitable because of increased permeability of neuronal membranes to sodium. This results in hyper-reflexia as well as spontaneous, asynchronous & involuntary contractions of skeletal muscles (_______).
calcium, falls, tetany
A typical attack of hypocalcemic tetany involves muscular spasms in the face (____________ sign) and characteristic contortions of the arms and hands (________ sign).
Chvostek's sign, Trousseau's sign
Pronounced (hypocalcemia or hypercalcemia) may produce more generalized muscular contractions and convulsions. Laryngeal spasm and contraction of respiratory muscles may compromise breathing.