Which of the following is a primary function of FSH (Follicle Stimulating Hormone)?

Follicle Stimulating Hormone (FSH) plays a crucial role in the reproductive system, particularly in regulating the development and function of the gonads in both sexes. In females, one of the primary functions of FSH is to stimulate the growth and maturation of ovarian follicles, which contain the developing eggs. This process is vital for establishing a menstrual cycle and promoting ovulation. The rise of FSH levels leads to the development of these follicles and the eventual release of an egg during ovulation.

In males, while FSH does contribute to reproductive function by stimulating Sertoli cells to aid sperm production, the main focus of the question is on its role in females, making stimulation of egg production the correct answer. In contrast, the other options address functions unrelated to FSH: regulating metabolism and controlling kidney function are associated with different hormones, while testosterone production is primarily stimulated by Luteinizing Hormone (LH).