hypogodadic hypogonadism

A 21-year-old male is referred to the endocrine clinic with poorly developed secondary sexual characteristics. The only relevant finding on history is that he has a very poor sense of smell.

On examination he has no axillary or pubertal hair, a 3 cm penis and testicular volumes of approximately 5 ml bilaterally. Smell test reveals that he is unable to distinguish acetone and coffee.

Investigations reveal:

Testosterone 4 nmol/l (10-30)
Prolactin 380 mU/l (<450)
FSH 2.1 IU/l (1-7)
LH 1.5 IU/l (1-10)

What is the most likely diagnosis?

(Please select 1 option)

5-alpha reductase deficiency
Kallman’s syndrome This is the correct answerThis is the correct answer
Klinefelter’s syndrome
Microdeletion of the Y chromosome IncorrectIncorrect answer selected

This patient has evidence of hypogonadotrophic hypogonadism with a low testosterone and a low follicle-stimulating hormone (FSH) and luteinising hormone (LH). In this case, there is isolated gonadotrophic deficiency as evidenced by a normal prolactin. This is seen in Kallman’s syndrome, which is often associated with anosmia.

In Klinefelter’s syndrome an elevated LH/FSH would be expected, as this is due to testicular failure as would be the case in 5-alpha reductase deficiency.

Craniopharyngioma is a possibility as it does cause hypogonadotrophic hypogonadism but abnormalities in sense of smell would not be expected.

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