What role does luteinizing hormone (LH) play in the male reproductive system?

Luteinizing hormone (LH) plays a crucial role in the male reproductive system primarily by stimulating the Leydig cells in the testes to produce testosterone. This hormone is vital for the development and maintenance of male secondary sexual characteristics, libido, and overall reproductive function.

When LH is secreted from the anterior pituitary gland in response to gonadotropin-releasing hormone (GnRH) from the hypothalamus, it specifically binds to receptors on Leydig cells, which are responsible for testosterone production. Thus, the secretion of testosterone directly influences sperm production and overall male fertility, along with impacting muscle and bone mass.

In contrast to the other choices, LH does not directly stimulate sperm production, promote the development of the placenta, or facilitate muscle development independently of testosterone levels. Therefore, understanding LH's direct role in testosterone regulation is essential for comprehending male reproductive physiology.