USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

What are the hormonal changes seen in males with Leydig cell dysfunction leading to primary hypogonadism?

1. ↓FSH, LH, testosterone, sperm count

2. ↓testosterone, sperm count; ↑LH; ↑FSH

3. ↑FSH, LH, testosterone, sperm count

4. Normal levels of all hormones

The correct answer is: ↓testosterone, sperm count; ↑LH; ↑FSH

Leydig cells are responsible for producing testosterone in males. When there is dysfunction in these cells, it leads to reduced testosterone levels. This decrease in testosterone is significant because it impacts various functions including libido, spermatogenesis, and overall male hormonal balance. In response to low testosterone levels, the hypothalamus and pituitary gland sense the deficiency and attempt to compensate. The hypothalamus increases the secretion of gonadotropin-releasing hormone (GnRH), which in turn prompts the anterior pituitary gland to release more luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Increased levels of LH occur because it is directly tied to the stimulation of Leydig cells for testosterone production. However, in the case of Leydig cell dysfunction, even with elevated LH levels, testosterone production remains impaired, resulting in low testosterone. On the other hand, FSH, which primarily regulates spermatogenesis via its action on Sertoli cells, may be elevated as well due to the reduced feedback inhibition from testosterone and inhibin B. Consequently, both LH and FSH can be elevated in response to the dysfunction of Leydig cells alongside the low testosterone levels and reduced sperm count. In summary, in males with Leydig cell dysfunction leading