Flashcards in Hyperthyroidism Deck (19)
Describe how thyroid hormone is made.
Iodine taken up into cuboidal epithelial cells of thyroid
I- -->I2 via oxidation by peroxidase
Tg + I2 organification
Tg/I2-->MIT or DIT by adding tyrosines and iodine
MIT/DIT-->T3/T4 via condensation.
More T4 made than T3.
Stored in Colloid, enough for 2-3 mo.
When needed, proteolytic release from Tg. T3/T4 released into blood.
In the periphery, T4-->T3 (active form)
What are some things that can decrease thyroid binding globulin? What does this do to levels of thyroid hormone?
Low protein states, low TBG
Total T3/T4 decreased
Free T3, T4 same.
What are some things that can increase thyroid binding globulin? What does this do to levels of thyroid hormone?
Pregnancy, OCP can increase TBG
Total T3/T4 increase.
Free T3/T4 same.
If you suspect thyrotoxicosis, but thyroid levels are normal. What could the possible cause be?
What are 2 conditions that could cause neg. results on radioactive iodine uptake?
1. subacute thyroiditis. Painful tender thyroid.
2. factitious hyperthyroidism: taking exogenous T3/T4 for weight loss or something. Sometimes seen in health care workers.
Describe the presentation of a thyroglossal duct cyst.
anterior midline neck mass
moves w/ swallowing
What is the remnant of the thyroid tissue?
foramen cecum is the normal remnant of the thyroglossal duct
another remnant that is possible is the pyramidal lobe of the thyroid
What are the 4 functions of T3?
beta adrenergic effects
basal metabolic rate increases
What does hyper/hypothyroidism do to cholesterol levels? GI motility?
hypothyroidism: increased cholesterol in blood (decrease in LDL receptors)
hyperthyroidism: decreased cholesterol in blood (increase in LDL receptors)
T/F the hot nodules of the toxic multi nodular goiter are malignant.
False. benign, but do secrete excess T3/T4
What is the presentation of a thyroid storm?
stress-induced catecholamine surge
What are the 3Ps of treatment for thyroid storm?
What is Jod-Basedow Phenomenon?
when those w/ iodine deficiency (hypothyroidism) or hyperthyroidism take in a bunch of iodine in diet, contrast dye, or amiodarone. Can get thyrotoxicosis.
What is the MOA of propylthiouracil?
inhibits organification of thyroglobulin and I2 via peroxidase enzyme
inhibits peripheral conversion T4-->T3
What are the side effects of PTU?
can cause hypothyroidism in fetus if used during pregnancy
still: preferred to methimazole for use during pregnancy in the 1st trimester
What is the MOA of methimazole?
inhibits peroxidase (organification of TG & I2)
What are the SE of methimazole?
can cause fetal hypothyroidism or fetal aplasia cutis
preferred to PTU in 2nd or 3rd trimesters of pregnancy
Aside from PTU or methimazole, what are other treatments for hyperthyroidism?
**require treatment for hypothyroidism afterwards