Final answer:
Luteinizing Hormone (LH) is the primary stimulus for Leydig cells in the testes to produce testosterone, as part of a regulatory mechanism involving the hypothalamus and pituitary gland.
Step-by-step explanation:
Leydig cells in the testes are stimulated to produce testosterone predominantly by the hormone Luteinizing Hormone (LH). The regulation of Leydig cell testosterone production is orchestrated by the hypothalamus and pituitary gland through a hormonal cascade. The hypothalamus secretes gonadotropin-releasing hormone (GnRH), which then stimulates the anterior pituitary gland to secrete LH. When LH binds to receptors on Leydig cells, it upregulates testosterone production, playing a crucial role in the male reproductive system.
It is important to note that although Follicle Stimulating Hormone (FSH) is also stimulated by GnRH, it acts on the Sertoli cells to support sperm maturation and not directly on the Leydig cells. The other hormones mentioned, inhibin and GnRH itself, do not directly stimulate Leydig cells to produce testosterone.