CAH is associated with reduced fertility in both females and males.
Fertility and the pregnancy rate are reduced in female patients, both with classic and non-classic forms of the disease, although non-classical forms are affected only mildly. Long-term anovulation and endometrial dysfunction are two characteristic fertility-related symptoms in women with CAH. Both of these symptoms can be attributed to the elevated androgens, mainly testosterone, in the serum. The excess of testosterone suppresses the pituitary, which then does not stimulate the ovaries to release oocytes. Furthermore, testosterone may interfere with the function of ovarian cells directly.
Another cause of subfertility is elevated progesterone, which can be produced by conversion from the adrenal testosterone. Progesterone may then impair ovulation, and hinder implantation by altering the endometrium. Another reported effect of elevated progesterone is thickened cervical mucus, which may prevent the sperm from entering the uterus, therefore acting as contraception.
In men, reduced fertility may be due to two main factors. The first one is testicular dysfunction, caused by lower production of luteinizing hormone. The luteinizing hormone secretion is supressed by the excessive amounts of adrenal testosterone, which in turn causes dysfunction of the Leydig cells in the testes and low testicular testosterone. This inhibits sperm production, leading to reduced sperm count, or even azoospermia of non-obstructive type. Sertoli cells, which are also important in the development of the sperm, are usually also affected, as the amount of their product, inhibin B, is usually lower in males with CAH. Sertoli cell dysfunction then contributes to testicular failure to produce sperm cells.
The second factor is the increased risk of testicular adrenal rest tumors (TART). These tumors arise from aberrant adrenal cells present in the testis that grow in number due to stimulation by ACTH. TART is a significant risk factor for both Leydig and Sertoli cell dysfunction, because it damages the testicular tissue due to its growth. Furthermore, the TART may obstruct the seminiferous tubules of the testis, which in turn may also lead to azoospermia.