Primary hypogonadism (congenital or acquired): Testicular failure due to diseases and conditions in the body such as cryptorchidism, bilateral torsion, orchitis, vanishing testis syndrome, orchiectomy, Klinefelter Syndrome, chemotherapy, or toxic damage from alcohol or heavy metals; these men usually have low serum testosterone levels and gonadotropins (FSH, LH) above normal range Hypogonadotropic hypogonadism (congenital or acquired): Gonadotropin or luteinizing hormone-releasing hormone (LHRH) deficiency or pituitary-hypothalamic injury from tumors, trauma, or radiation; these men have low testosterone serum concentrations but have gonadotropins in the normal or low range.
Testosterone, an essential precursor of estrogen in women, is made in the ovaries and adrenal glands. There is a steady decline in testosterone levels from the 20s through menopause. With surgical menopause, the level of testosterone drops precipitously. No clear lower limit of testosterone has been established; however 15 ng per dL ( nmol per L) commonly is used. One study 38 found that women with 0 to 10 ng per dL (0 to nmol per L) had markedly decreased sexual desire in all situations and absent or markedly decreased orgasms. Because of studies like this, supplemented with anecdotal evidence, many women have been started on testosterone therapy.
Bone Density: An important factor to consider
In general, the maintenance of healthy bone density in all people is partly dependent on both estrogen and testosterone levels. When an individual's body produces estrogen as its main sex hormone (as in the case of female-bodied people), that estrogen in healthy levels protects against bone loss. If a female-bodied person were to begin testosterone therapy, there would be a time of transition in the body while hormone levels adjust. While testosterone would soon become a more dominant presence in the body of a trans man, he would still retain some estrogen in his system, both through the presence of his ovaries (if he has not had an oophorectomy) and/or via the natural aromatization of testosterone into estrogen (which takes place whether or not the ovaries are still present and functional).