For a long period of time humans could not answer the question of what makes a man, a man, and a women, a women. As was recently found main difference is not just in presence of genitals. Probably one will ask why? The answer is that genitals themselves are indirect products of another matter. The name of this matter is testosterone.
“Testosterone is a hormone that stimulates sexual development in male human beings. It belongs to a family of hormones called androgens. Primarily the testicles, a part of male sex glands, produce androgens. The ovaries in females and the adrenal glands in both sexes also yield small amounts of testosterone and other androgens (The world book encyclopedia).”
In its earliest crucial functions, in developing embryo, testosterone play the key role in telling the cells of the genetically male embryo to develop as a male. It is amazing, but all human embryo begins as females for the first few weeks of an embryo’s life, a small group of cells have potential to develop either as ovaries or testes. About one million of genes that are needed to direct the development of a human being, one single gene (the “SRY” gene), which is carried on the Y chromosome, is responsible for determining the sex of the embryo. If the embryo’s cells contain the “SRY” gene, the embryo will develop testes, which at some point and for a limited period of time early in its development produce and release a big amount of testosterone. It turn, testosterone then signal the cells of other parts of the embryo to develop as a male.
As shown in the study by a Stanford research group namely testosterone is responsible for formation of genitals. An experiment was held on newborn female rats. They were injected with testosterone. Surprisingly, but the female rats developed male genitals, and female genitals began disappearing. Later “converted” female rats started revealing purely male behavior, and they were fully aware of usage of their “new” male genitals. The same experiment was performed with male newborn rats. It is amazing, but their penises withered and later completely disappeared. This experiment is not ethical to perform on humans, but random facts suggest that all most the same can be done with humans. For instance, in lesbian couple, butches (female that represents male) use testosterone injections to develop male features such as deep voice, facial hair and muscles (“The He Hormone,” Andrew Syllivan)
In girls, the adrenal glands begin to produce testosterone earlier than in boys. That’s is how and why girls mature earlier, as a rule, than boys. It was testosterone that stimulated the growth of girls pubic hair and underarm hair (there are testosterone receptors in the skin of the pubic area and the skin of the underarm that are genetically programmed to react to testosterone by producing hair). And testosterone stimulated girls skin to produce more oil, contributing to the acne of girls early teenage years, but also to the healthy glow of the skin and the shine of the hair.
The medical book Reproductive Endocrinology by Drs. Samuel Yen and Rovert Jaffe, states; “Testosterone and other androgens have some biological activity o virtually every tissue in the body.” Among the most important functions listed are “anabolic actions, such as stimulation of linear body growth, nitrogen retention, and muscular development.” This statement means that testosterone works to keep the cells of the body functioning efficiently, making the best use of nourishment of growth and maintenance, and particularly contributing to the health of bones and muscles.
Having knowledge of the way testosterone function in the body, artificial testosterone injections can be used for variety of purposes. One of the purposes of artificial use of testosterone is to stimulate sex drive. The balance of this hormone is responsible for initiating and maintaining the production of sperm from early puberty throughout adulthood in male body. During childhood and adolescence, these hormones are responsible for:
1) Growth of genitals
2) Depth of pitch of the voice, increase muscle mass, and growth of bones.