A 17-year-old Tanner stage 2 female presents with a history of bilateral spontaneous milky discharge from her breasts for 2 months. Menarche was at age 12 years, and her periods had been regular until 4 months before this visit to your office. In addition, she complains of headache on awakening for the past 2 weeks. The most useful screening test is

Correct Answer: C

Rationale: Galactorrhea (milky discharge), amenorrhea, and headaches suggest hyperprolactinemia, possibly from a pituitary adenoma. Serum prolactin level (C) is the most useful initial test. Rationale: Pregnancy tests (A, B) are relevant but less likely given Tanner stage 2 and no sexual history implied; prolactin directly assesses the suspected cause, unlike estrogen (D) or LH (E, not listed).

Correct Answer: B

Rationale: Bromocriptine (B), a dopamine agonist, is first-line for prolactinomas, shrinking tumors and normalizing prolactin. Rationale: Surgery (A) is for large/non-responsive tumors; Ondansetron (C) treats nausea, phenothiazine (D) increases prolactin, and antidepressants (E) are unrelated.

Correct Answer: D

Rationale: NF2 (A), Huntington (B), Marfan (C), are AD; Friedreich ataxia (D) is AR (GAA repeat on chromosome 9). Rationale: AD disorders need one allele; FRDA requires two.

Correct Answer: B

Rationale: Color blindness (B) is the most common XLR disorder (1 in 12 males). Rationale: Hemophilia (D) and fragile X (E) are less frequent; Rett (A) is XLD.

Correct Answer: B

Rationale: PWS is most commonly due to paternal 15q11-13 deletion (B, ~70%). Rationale: Maternal deletion (A) causes Angelman; paternal UPD (C) is less common (~25%).