Question

(a) All of the following are associated with hypergonadotrophic hypogonadism in males, except: (Klinefelter, Noonan, viral orchitis are causes; one option is not). (b) Which of the following is the most common cause of hypergonadotrophic hypogonadism in males? Options for both parts: A. Viral orchitis, B. Klinefelter's syndrome, C. Kallmann's syndrome, D. Noonan syndrome.

• A. Viral orchitis
• B. Klinefelter's syndrome
• C. Kallmann's syndrome
• D. Noonan syndrome

Hint:

Kallmann's gives LOW gonadotropins, the others raise them.

Answer 1

The Correct Option is C

Step 1: Define the two types. Hypergonadotrophic hypogonadism means the testis (the gonad) has failed, so testosterone is low and the pituitary responds by pushing FSH and LH high (primary testicular failure). Hypogonadotrophic hypogonadism means the problem is above the testis, in the pituitary or hypothalamus, so the gonadotropins FSH and LH are low (secondary hypogonadism).
Step 2: Answer part (a), the exception. Viral orchitis (for example mumps), Klinefelter's syndrome (47,XXY) and Noonan syndrome all damage the testis directly, so all three are hypergonadotrophic (high gonadotropins). Kallmann's syndrome is the odd one out, because it is a failure of GnRH neuron migration with anosmia, giving LOW gonadotropins. So Kallmann's is NOT a cause of hypergonadotrophic hypogonadism. The exception is option C, Kallmann's syndrome.
Step 3: Answer part (b). Among the listed primary testicular causes, Klinefelter's syndrome (47,XXY) is the most common cause of primary (hypergonadotrophic) hypogonadism and the commonest cause of congenital male hypogonadism overall. Note: the printed key labelled part (b) as hypogonadotrophic, but Klinefelter's is a hypergonadotrophic disorder. Klinefelter's is the correct most common cause of hypergonadotrophic hypogonadism, which is the medically consistent reading.
Step 4: Reconcile the keys. For part (a) the answer is C (Kallmann's, the exception). For part (b) the answer is B (Klinefelter's, the commonest primary cause). Since this row records part (a) as the lead, the marked answer is option C.
Conclusion: Part (a) exception is Kallmann's syndrome, option C; part (b) commonest primary cause is Klinefelter's syndrome.