Hypothyroidism Flashcards
What are the muscles that overlie the Thyroid gland?
SCM
Omohyoid
Sternohyoid
How do you palpate the thyroid gland?
Superior to inferior, from the hyoid cartilage, have them swallow, and compare
Why use your stethoscope with hypothyroidism?
May hear a bruit
sign***
What is the first step of thyroid hormone synthesis?
Trapping of Iodide by the Na/I symporter
What is the second step of thyroid hormone synthesis?
Trapping–TPO catalyzes iodine oxidation to thyroglobulin
What is the third strep of thyroid hormone synthesis?
COupling–MITs and DITs
What is the Jod Basedow effect?
Initial increase in organification with iodide synthesis
What is the Wolff-Chaikoff effect?
Very high concentrations of iodide actually inhibit organification of T4
What is the Escape phenomenon with thyroid function?
AT extremely high iodide concentrations, organification will resume
How is T4 converted to T3?
5’ Deiodination in the periphery by deiodinase
What are the two subunits of TSH? What is the function of each
Alpha subunit
Beta subunit = active part
What happens to prolactin levels with TRH levels?
May increase. Thus hypothyroidism may cause prolactin
Why is it that a woman who is hypothyroid may have high levels of prolactin?
TRH causes increase in prolactin
What is the major output of the thyroid gland?
T4 (95% of secretion)
What is the process that converts T4 to T3 in the periphery?
5’ Deiodination
What is the half life of T4? T3?
T4 = 7 days T3 = 1 day
True or false: thyroid hormone bound to proteins have no biological effect?
True
What is the purpose of transporting thyroid hormone bound to protein?
Allows for a reserve and a buffer
What percent of T4 and T3 are “free” in the serum?
T4 = 0.04% T3 = 0.4%
What is the main protein that binds thyroid hormone?
Thyroid binding globulin
What are the labs that are evaluated for thyroid issues?
Free T4 and FT3 vs T4
What are the factors that may increase TBG levels? (2)
Estrogen (pregnancy, BCP)
What are the factors that decrease TBG? (3)
Systemic illness
Glucocorticoids
Cirrhosis
What is the main lab test to assess for thyroid function? Why?
TSH levels are the most sensitive and are less prone to fluctuations
What is the relationship to TSH with hypo/hyperthyroidism?
Inverse
Why is T3 not a good lab test to order?
Prone to fluctuations
Which is better: T4 levels or total thyroid hormone?
T4
What is the relationship between TSH and FT4?
Inverse
What happens to TSH levels as you progress from hypo to hyperthyroidism?
Decreases
What are the tests that assess for autoimmune thyroid dzs? What is the problem with this?
Thyroperoxidase Ab
Super sensitive to any sort of autoimmune disease
What are the three ab that can be obtained for suspected autoimmune thyroid dz?
Thyroperoxidase
Thyroglobulin
Thyrotropin ab