Effects of Radioactivity towards Human Reproductive Organs

Radiation effects are varying with the dose, dose rate, sex and age. In males, spermatogonia are the most radiosensitive whereas for spermatozoa and spermatids are radioresistant. In general, radiation could cause sterility effect that warrants special attention. When the testis received a scattered dose from nearby abdominal and pelvic irradiation field, this may directly affect the gonads thus leading to infertility and impaired sex steroid production. In general, lethally irradiated cells die during division. A direct radiation dose as low as 0.15 Gray (Gy) is able to cause a significant depression in the sperm count and temporary azoospermia occurring after exposure to doses of 0.3 Gray. Furthermore, after exposing to doses as low as 1 Gy both of their numbers and that of their daughter cells, the preleptotene spermatocytes, are severely reduced. The doses of irradiation required to kill spermatocytes are higher than for spermatogonia whereby 2-3 Gy is able to result in an inability to complete maturation division, with a resultant decrease in spermatid numbers. However, spermatids show no overt damage, but after 4-6 Gy the resultant spermatozoa are significantly decreased in number, signifying covert spermatid damage (Amanda L. et al., 1993).Hence male sterility will have a reduced sperm count and low motility. Other than this, irradiation of the testis might occur during therapeutic, diagnostic procedures and occupational exposure. Irradiation of the testis during the radiotherapy treatment of cancer usually involves fractionated exposures. Under certain conditions, fractionation results more stem cell to be killed than single dose treatments, although this has not been proven in man (Hahn et al.). In addition, radiation might also result from accidental exposure. For instance during nuclear reactor accidents, this exposure may result in whole body exposure at doses below the threshold for lethality but above those capable of inducing long-term sperm count depression.

In females, ovarian follicles are the most radiosensitive. The radiosensitivity of the oocyte varies during the growth phase and is dependent on the age, the strain of the animal, and the species. In women, primordial oocytes are more resistant to the effects of radiation than oocytes in growing follicles. Other than this, permanent sterility which is manifested by the damage to the ovarian follicles occurs with 320 to 625cGy of the irradiation. However, follicles may recover in 5 to 6 months if the dose is lower. In younger women, relatively large dose are required to cause the damage than in older women. As radiation could cause a devastating effect in the embryo and fetus in expectant mothers, diagnostic radiological and nuclear medicine procedures are contraindicated for them. This is due to radiopharmaceuticals will reside in the body following a biological half-life, therefore it is more likely to cross the placenta thus cause fetal damage and may have a higher rate of miscarriage or stillborn baby. In those women whom the uterus has been involved in the radiation field, there is evidence that radiation changes to the uterus result in failure to carry a pregnancy, which has implications for in vitro fertilization in women with concomitant ovarian failure (Amanda L. et al., 1993).