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Klinefelter’s syndrome occurs when a man is born with one or more extra X chromosomes, leading to a variety of impacts that include underdeveloped testicles, impaired testosterone production ...
Testosterone is the primary male sex hormone and androgen in males. [3] In humans, testosterone plays a key role in the development of male reproductive tissues such as testicles and prostate, as well as promoting secondary sexual characteristics such as increased muscle and bone mass, and the growth of body hair.
Leydig cells release a class of hormones called androgens (19-carbon steroids). [8] They secrete testosterone, androstenedione and dehydroepiandrosterone (DHEA), when stimulated by the luteinizing hormone (LH), which is released from the anterior pituitary in response to gonadotropin releasing hormone which in turn is released by the hypothalamus.
The masculinization of the embryonic reproductive structures occurs as a result of testosterone secreted by the embryonic testes. Testosterone, however, is not the active agent within these organs. Once inside the target cells, testosterone is converted by means of an enzyme called 5α-reductase into the dihydrotestosterone (DHT).
Men with low serum testosterone levels should have other hormones checked, particularly luteinizing hormone to help determine why their testosterone levels are low and help choose the most appropriate treatment (most notably, testosterone is usually not appropriate for secondary or tertiary forms of male hypogonadism, in which the LH levels are ...
If conception does not occur, decreasing excretion of progesterone will allow the hypothalamus to restart secretion of GnRH. These hormone levels also control the uterine (menstrual) cycle causing the proliferation phase in preparation for ovulation, the secretory phase after ovulation, and menstruation when conception does not occur.
The researchers, who relied on animal testing to conduct the study, found the opposite was true when it came to testosterone, the male hormone produced mainly in the testes, and testicle size.
The challenge hypothesis makes different predictions regarding testosterone secretion for species in which males exhibit paternal care versus those in which males do not. When aggressive interactions among males arise in species that exhibit paternal care, testosterone levels are expected to be elevated.