Final answer:
Testosterone secretion by the testes starts soon after testis formation, with Leydig cells producing testosterone by the seventh week of embryonic development, peaking in the second trimester. Testosterone levels remain low in childhood and rise significantly during puberty to contribute to the development of male reproductive structures and secondary sexual characteristics.
Step-by-step explanation:
The testis begins to secrete testosterone soon after its formation. This process is initiated by the Leydig cells, which are crucial in the development of male reproductive structures. During male embryonic development, Leydig cells start producing testosterone by the seventh week, reaching peak levels in the second trimester. This secretion plays a critical role in the anatomical differentiation of the male sexual organs. Nonetheless, during childhood, the levels of testosterone are low and only rise significantly at the onset of puberty. At puberty, the hypothalamus triggers the release of follicle-stimulating hormone (FSH) and luteinizing hormone (LH). LH stimulates the Leydig cells to produce and release more testosterone, which in turn stimulates spermatogenesis and contributes to the development of secondary sexual characteristics such as facial and pubic hair, deepening of the voice, and increased muscle mass.