Effect of radiation on the human reproductive system.

Irradiation may have a profound effect on reproductive function. The schedule of the delivered irradiation (total dose, number of fractions, and duration) is an important determinant of the radiobiological effect on the tissues involved and varies among different tissues and organs. Irradiation to the central nervous system may affect the timing of the onset of puberty, result in hyperprolactinemia, or cause gonadotropin deficiency if the hypothalamic-pituitary axis is involved in the radiation field. Direct irradiation to the testis will, in lower doses, affect the germinal epithelium: doses of irradiation greater than 0.35 Gy cause aspermia, which may be reversible. The time taken for recovery increases with larger doses; however, with doses in excess of 2 Gy aspermia may be permanent. At higher radiation doses (> 15 Gy), Leydig cell function will also be affected. In addition to radiation dose, the vulnerability of the testis is dependent on the age at irradiation and the pubertal status of the male. In the female, the response of the ovary to the effects of irradiation varies with age as well as dose, and separation of ovarian dysfunction into hormonal and fertility effects is not clearcut. An ovarian dose of 4 Gy may cause a 30% incidence of sterility in young women, but 100% sterility in women over 40 years of age. Pelvic irradiation may also have a profound effect on the uterus, with arrested growth in the prepubertal girl, and failure of uterine expansion during pregnancy with subsequent miscarriages and premature labor.