375 Thyroid Gland Physiology and Testing Flashcards
Normal weight of thyroid gland (H20 C375 P2692)
12-20 g
The thyroid gland develops from the floor of the primitive pharynx during what week of gestation? (H20 C375 P2692)
3rd week
Thyroid hormon synthesis begins at about how many weeks’ gestation?
11 weeks
Protein precursor of thyroid hormones (H20 C375 P2692)
Thyroglobulin
The most useful physiologic marker of thyroid hormone action (H20 C375 P2692)
TSH
The major positive regulator of TSH synthesis (H20 C375 P2693)
TRH
Dominant regulator of TSH production (H20 C375 P2693)
Thyroid hormones
Peak TSH secretion occurs how many minutes after exogenous TRH? (H20 C375 P2693)
15 minutes
Plasma half-life of TSH
50 mins
Critical first step in thyroid hormone synthesis (H20 C375 P2693)
Iodide uptake
A disorder characterized by defective organification of iodine, goiter, and sensorineural deafness, caused by a mutation of the pendrin gene (H20 C375 P2693)
Pendred syndrome
Most common cause of preventable mental deficiency (H20 C375 P2693)
Iodine deficiency
RDA for iodine for pregnant women (H20 C375 P2694)
220 μg
Urinary iodine in iodine-sufficient populations (H20 C375 P2694)
> 10 μg/dL
Uncoupled mono- and diiodoty- rosines (MIT, DIT) are deiodinated by this enzyme (H20 C375 P2694)
Dehalogenase
A phenomenon where excess iodide transiently inhibits thyroid iodide organification (H20 C375 P2694)
Wolff-Chaikoff effect
Women with a precarious iodine intake of this amount are most at risk of developing a goiter during pregnancy or giving birth to an infant with a goiter and hypothyroidism. (H20 C375 P2694)
<50 μg/d
The World Health Organization recommends a daily iodine intake of this amount during pregnancy and lactation (H20 C375 P2694)
250 μg
RDA for iodine for breastfeeding women (H20 C375 P2694)
290 μg
Prenatal vitamins should contain this amount of iodine per tablet. (H20 C375 P2694)
150 μg
hCG- induced changes in thyroid function can result in this condition, that may be associated with hyperemesis gravidarum. (H20 C375 P2694)
Transient gestational hyperthyroidism
Total T4 and T3 levels are about how many times higher throughout pregnancy (H20 C375 P2694)
1.5×
Serum half-life of T4 (H20 C375 P2695)
7 days
Thyroid hormone requirements are increased by up to ___ during pregnancy in levothyroxine-treated hypothyroid women. (H20 C375 P2695)
45%
Protein that carries about 80% of bound thyroid hormones (H20 C375 P2695)
TBG
Most important source of reveres T3 (H20 C375 P2696)
Type III deiodinase
An autosomal dominant disorder characterized by elevated thyroid hormone levels and inappropriately normal or elevated TSH. (H20 C375 P2696)
Resistance to thyroid hormone (RTH)
Provides definitive diagnosis of RTH (H20 C375 P2696)
DNA sequence analysis of the TRβ gene
Provides the most accurate measurement of thyroid volume and nodularity and is useful for assessment of goiter prevalence in iodine deficient regions.
Ultrasound imaging
Sign characterized by difficulty breathing especially when the arms are raised. (H20 C375 P2697)
Pemberton’s sign
It is reasonable to only measure antibodies to this protein when considering autoimmune thyroid disease (H20 C375 P2697)
TPO antibodies
Serum Tg levels are increased in all type of thyrotoxicosis except: (H20 C375 P2697)
Thyrotoxicosis factitia
