**Question:** Follicle stimulating hormone (FSH) receptors are present on:

**Core Concept:** Follicle-stimulating hormone (FSH) is a gonadotropin hormone produced by the anterior pituitary gland that plays a crucial role in regulating the menstrual cycle and spermatogenesis. FSH receptors are specific proteins on target cells that interact with FSH to initiate a response.

**Why the Correct Answer is Right:**
FSH receptors are present on cells that require FSH stimulation for their function. In females, these include granulosa cells in the ovarian follicles, which are essential for the development and maturation of ovarian follicles and subsequent estrogen production. In males, FSH receptors are found on Sertoli cells in the testes, which support spermatogenesis and hormone production.

**Why Each Wrong Option is Incorrect:**
A. Germ cells in the testes: Although FSH plays a role in spermatogenesis, the correct answer is D (Sertoli cells), not A (germ cells).
B. Leydig cells in the testes: While Leydig cells produce testosterone, their primary function is not dependent on FSH. The correct answer is D (Sertoli cells), not B (Leydig cells).
C. Ovarian theca cells: Theca cells produce androgen hormones, but their function is not directly related to FSH receptors. The correct answer is D (Sertoli cells), not C (theca cells).
D. Sertoli cells in the testes: As mentioned earlier, FSH receptors are indeed present on Sertoli cells. These cells support spermatogenesis and hormone production, making this the correct answer.

**Clinical Pearl:**
Understanding FSH receptors and their specific targets is crucial for understanding fertility and male reproductive health. A deficiency or excess of FSH can lead to issues like infertility, precocious puberty, or delayed puberty, depending on the gender. This highlights the importance of this hormone and its receptors in reproductive health.

**Correct Answer:** D. Sertoli cells in the testes