Estrogens are most commonly used in combined hormonal contraception and hormonal replacement therapy in postmenopausal women. Therefore, in hormonal contraception, they are used to directly impair the woman’s fertility at the moment, and in hormonal replacement therapy are used in patients that have already completed their fertile period. However, hyperestrogenism resulting from estrogen administration may cause menstrual irregularities, amenorrhea and subsequent infertility in otherwise healthy women.
In men, estrogens can be administered in the treatment of some hormone-sensitive cancers, most notably prostate cancer. Estrogens act as anti-androgens, disrupting the growth stimulation of the tumour by androgens. However, the side effects of estrogen therapy in men can reduce both fertility and life quality of the patient. Due to supressed testosterone activity, the patients may experience feminization (development of female physical characteristics), gynecomastia, sexual dysfunction due to combined reduced sex drive and erectile dysfunction, hypogonadism (decreased function of the testes) and infertility.
Progesterone and progestins
Progestins can be used to reduce the adverse effects on fertility caused by estrogen excess, such as anovulation and endometrial hyperplasia. Progesterone and progestins are also used during the luteal phase of the menstrual cycle to increase the chances of success of IVF procedure – a practice known as luteal support. They prepare the uterine lining for implantation and support early pregnancy.
Progestins are also used in combined or progestin-only hormonal contraception. They mimic the effects of progesterone and supress the release of gonadotropin from the pituitary, creating a state of reversible infertility (fertility is restored if their administration is discontinued).
In men, administration of progestins can similarly lead to gonadotropin suppression, reduced testosterone secretion, and therefore, reduced fertility.
Exogenous androgens mimic the functions of testosterone in the body, and therefore lead to an increase in muscle mass and sex drive. However, they inhibit the release of gonadotropins through the negative feedback mechanism, and thus impair the hormonal stimulation necessary for the function of the testes. The testes then produce less testosterone, which is needed directly in the testicular fluid for healthy spermiogenesis. Without testicular testosterone production, the spermiogenesis is ineffective and may cease completely. This eventually leads to failure of the testes to produce sperm, called non-obstructive azoospermia, which is a direct cause of male infertility.
Androgen administration in women disrupts gonadotropin and female sex hormone secretion, leading to menstrual irregularities, amenorrhea, breast atrophy, hypogonadism and infertility. Anabolic androgens are also teratogenic during pregnancy (may cause damage to the fetus).