Hyperthyroidism

Question 1

Describe how thyroid hormone is made.

Answer 1

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)

Question 2

What are some things that can decrease thyroid binding globulin? What does this do to levels of thyroid hormone?

Answer 2

Low protein states, low TBG
--nephrotic syndrome
--liver disease
Total T3/T4 decreased
Free T3, T4 same.

Question 3

What are some things that can increase thyroid binding globulin? What does this do to levels of thyroid hormone?

Answer 3

Pregnancy, OCP can increase TBG
Total T3/T4 increase.
Free T3/T4 same.

Question 4

If you suspect thyrotoxicosis, but thyroid levels are normal. What could the possible cause be?

Answer 4

menopause
panic attack
anxiety
pheochromocytoma

Question 5

What are 2 conditions that could cause neg. results on radioactive iodine uptake?

Answer 5

1. subacute thyroiditis. Painful tender thyroid.
2. factitious hyperthyroidism: taking exogenous T3/T4 for weight loss or something. Sometimes seen in health care workers.

Question 6

Describe the presentation of a thyroglossal duct cyst.

Answer 6

anterior midline neck mass

moves w/ swallowing

Question 7

What is the remnant of the thyroid tissue?

Answer 7

foramen cecum is the normal remnant of the thyroglossal duct

another remnant that is possible is the pyramidal lobe of the thyroid

Question 8

What are the 4 functions of T3?

Answer 8

4Bs
brain maturation
bone growth
beta adrenergic effects
basal metabolic rate increases

Question 9

What does hyper/hypothyroidism do to cholesterol levels? GI motility?

Answer 9

hypothyroidism: increased cholesterol in blood (decrease in LDL receptors)
constipation
hyperthyroidism: decreased cholesterol in blood (increase in LDL receptors)
diarrhea

Question 10

T/F the hot nodules of the toxic multi nodular goiter are malignant.

Answer 10

False. benign, but do secrete excess T3/T4

Question 11

What is the presentation of a thyroid storm?

Answer 11

stress-induced catecholamine surge
agitation, delirium
fever
diarrhea
coma
tachyarrhythmia

Question 12

What are the 3Ps of treatment for thyroid storm?

Answer 12

3Ps
propranolol
PTU
prednisolone

Question 13

What is Jod-Basedow Phenomenon?

Answer 13

Iodine-induced hyperthyroidism
when those w/ iodine deficiency (hypothyroidism) or hyperthyroidism take in a bunch of iodine in diet, contrast dye, or amiodarone. Can get thyrotoxicosis.

Question 14

What is the MOA of propylthiouracil?

Answer 14

inhibits organification of thyroglobulin and I2 via peroxidase enzyme

inhibits peripheral conversion T4–>T3

Question 15

What are the side effects of PTU?

Answer 15

agranulocytosis
liver dysfunction
can cause hypothyroidism in fetus if used during pregnancy

still: preferred to methimazole for use during pregnancy in the 1st trimester

Question 16

What is the MOA of methimazole?

Answer 16

inhibits peroxidase (organification of TG & I2)

Question 17

What are the SE of methimazole?

Answer 17

agranulocytosis
can cause fetal hypothyroidism or fetal aplasia cutis
preferred to PTU in 2nd or 3rd trimesters of pregnancy

Question 18

Aside from PTU or methimazole, what are other treatments for hyperthyroidism?

Answer 18

beta blocker
radioactive iodine**
surgical resection**
**require treatment for hypothyroidism afterwards

Question 19

What is a weird teratoma that can cause hyperthyroidism?

Answer 19

struma ovarii–teratoma
has functional thyroid tissue
can cause hyperthyroidism