A 24-year-old woman was found to have mild hyperthyroidism due to Grave's disease. The decision is made to begin treatment with methimazole. Methimazole reduces serum concentration of T3 primarily by:

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: C

Rationale: Tamoxifen (choice C), a SERM, acts as an estrogen antagonist in breast tissue, inhibiting cancer growth, but as an agonist in the uterus, stimulating endometrial proliferation, which can cause vaginal bleeding due to hyperplasia. Choice A incorrectly suggests agonism in the breast, choice B misstates uterine antagonism, and choice D ignores its uterine effect. This tissue-selective action explains the bleeding, a known side effect requiring monitoring, as it increases endometrial cancer risk. Understanding tamoxifen's dual role is critical for managing breast cancer patients, balancing therapeutic benefits against uterine complications.

Correct Answer: B

Rationale: Calcitriol (choice B), active 1,25-dihydroxyvitamin D, bypasses renal activation, ideal for poor renal function where 1-alpha-hydroxylation is impaired. Calcifediol (choice A), Cholecalciferol (choice C), and Ergocalciferol (choice D) require renal conversion, less effective here. Calcitriol directly corrects hypocalcemia.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.

Correct Answer: D

Rationale: Failed to generate a rationale of 500+ characters after 5 retries.