What does follicle-stimulating hormone (FSH) primarily regulate?

Follicle-stimulating hormone (FSH) is primarily responsible for regulating the development and function of the reproductive system. In males, FSH plays a crucial role in promoting the production of sperm within the testes. It stimulates the Sertoli cells in the seminiferous tubules, which are essential for nurturing and supporting the development of sperm cells during spermatogenesis. This function is vital for male fertility.

In females, FSH is also important, as it stimulates the growth and maturation of ovarian follicles, which are critical for ovulation and the menstrual cycle. However, the question specifically addresses the primary regulation of FSH in males. Therefore, while both males and females are influenced by FSH, its direct and primary role in stimulating sperm production in males is the most accurate answer.

The other options do not reflect the primary function of FSH; testosterone production, for example, is primarily influenced by luteinizing hormone (LH), while insulin secretion is regulated by other hormones related to glucose metabolism, not FSH.