TH and Anti-Thyroid agents French

Question 1

What is TSH stimulated and inhibited by?

Answer 1

Stim by: hypothalamic TRH

Inhib by: somatostatin, DA, glucocorticoids (stress)

Question 2

pts who are on lithium ions for ani-manic therapy can show hyper or hypothyroidism? How?

Answer 2

HYPOthyroidism

- inhibits cAMP generation → less uptake of iodine → hence blocks action of TSH

Question 3

Iodide organification is achieved via which enzyme? What else does this enzyme do?

Answer 3

Thyroid peroxidase
I- oxidized and incorporated into tyrosine residues (MIT, DIT) on Tg molecules

It also is involved in coupling the MIT + DIT on Tg

Question 4

How is T4 and T3 released from the thyroid gland?

Answer 4

via proteolysis

Question 5

TRH aka _____
Pharmacodynamics
Uses

Answer 5

Protirelin
activ PLC → ↑ IP3 → ↑intracellular Ca2+

Test for pituitary reserve of TSH if suspected hypo or hyperthyroidism

Question 6

Thyrotropin
Pharmacodynamics
Uses

Answer 6

TSH
stimulates cAMP production → increased Iodide uptake + TH production

Uses: therapy for metastatic thyroid carcinoma

Question 7

Most common cause of hypothyroidism

Answer 7

autoimmune thyroiditis (Hashimotos)

• glandular destruction due to cell-antibody mediated damage
• nontender thyroid

Question 8

Why does pregnancy require increased T4 dose?

Answer 8

due to increased levels of TBG (via elevated estrogen) and placental metabolism of T4-T3

Question 9

Sign of end stage untreated hypothyroidism and is an acute medical emergency

Answer 9

Myxedema coma

- hyponatremia, hypoglycemia, hypothermia, shock, death

Question 10

Things that increase binding of free T4 to TBG

Answer 10

Estrogen (increases levels of TBG)
SERMs (Selective estrogen receptor modulators)
Tamoxifen

Question 11

Things that Decrease binding of free T4 to TBG

Answer 11

Salicylates

Antiseizure meds

Question 12

Where is the majority of circulating T3 that is utilized derived from and where? What about T3 that is used in brain and pituitary?

Answer 12

Derived from T4 in the liver

T3 that is utilized by pit+brain is derived locally

Question 13

Drugs that inhibit 5’deiodinase which converts T4 → T3

Answer 13

Glucocorticoids
Beta-adrenergic receptor antagonist
Propylthiouracil

Question 14

↑
→↓ ←

α β

Answer 14

v

Question 15

Most common form of hyperthyroidism

Answer 15

Graves disease

• results from thyroid stimulation by autoantibodies that mimic TSH
• see exophthalmos and pretibial myxedema

Question 16

Tx for graves disease

Answer 16

1. Symptomatic improvement: beta blockers, corticosteroids
2. Interfere with H production: Thionamides, Iodides
3. Glandular destruction: surgery, radioactive iodine

Question 17

Thionamides that block thyroid peroxidase
Use?
when should you be careful using them?

Answer 17

Methimazole, Propylthiouracil
Tx graves disease
Can be teratogen - careful if preggo
- if you have to use one during pregnancy, go with PTU

Question 18

Use of propanolol in hyperthyroidism

Answer 18

symptomatic relief

advantage of blocking T4→T3 conversion

Question 19

How to treat thyroid storm

Answer 19

3 P’s
Propanolol (BB) - control symp (tachy, atrial fib, ↑Cardiac Output)
Propylthiouracil - block H synthesis + T4 → T3
Prednisolone (Cortico) - prevents shock, block T4 → T3

*thyroid storm is a sudden. acute exacrbation of thyrotoxicosis (hyperthyroidism)