**Question:** FSH is secreted by:

A. Hypothalamus
B. Pars nervosa of the pituitary gland
C. Corpus luteum
D. Testes

**Core Concept:** FSH, luteinizing hormone (LH), and thyroid-stimulating hormone (TSH) are collectively known as the gonadotropins. These hormones are produced by the anterior pituitary gland, which is regulated by the hypothalamus. Gonadotropin-releasing hormone (GnRH) from the hypothalamus stimulates the anterior pituitary gland to produce FSH, LH, and TSH.

**Why the Correct Answer is Right:** FSH, along with LH, is produced by the pars nervosa (anterior) part of the pituitary gland. These hormones play a crucial role in regulating the menstrual cycle in females and spermatogenesis in males. FSH promotes the development and function of ovarian follicles and testicular spermatogenesis, respectively.

**Why Each Wrong Option is Incorrect:**

A. Hypothalamus: While the hypothalamus does secrete GnRH, which stimulates the pituitary gland to produce FSH and LH, it is not the source of these hormones themselves.
B. Pars intermedia: This term refers to the intermediate lobe of the pituitary gland, not the source of FSH production.
C. Corpus luteum: This is a temporary endocrine cell mass formed during the luteal phase of the menstrual cycle, not the source of FSH production.
D. Testes: FSH stimulates spermatogenesis in males, but it is produced by the pituitary gland, not the testes themselves.

**Clinical Pearl:** A proper understanding of the hormonal axis between the hypothalamus, pituitary gland, and gonads is essential for assessing fertility issues in patients and administering appropriate hormone replacement therapies.