Table 2.

Overview of different forms of Congenital Adrenal Hyperplasia and associated effects on fertility.

Forms of CAH	Effects on fertility
21-hydroxylase deficiency (61, 62, 63)	Classic Anatomic factors affecting sexual functioning Elevated androgens aromatised to oestrogens affecting HPG axis Elevated androgens directly inhibiting folliculogenesis Preferential secretion of LH that increases androgen levels Elevated progesterone impacting endometrium and HPG axis TARTs in male patients Psychosocial factors including increased prevalence of non-heterosexual preference Non-classic Elevated androgens affecting HPG axis leading to anovulation
11β-hydroxylase deficiency (118)	Resembles 21-hydroxylase deficiency without significant progesterone elevation
17α-hydroxylase deficiency/17,20-lyase deficiency (119, 120, 121)	Classic Sexual infantilism Failure to develop secondary sexual characteristics 46,XX – Müllerian structures with streak gonads 46,XY – blind vaginal pouch Hypergonadotropic hypogonadism Impaired spermatogenesis and folliculogenesis Non-classic Females – may develop secondary sexual characteristics with case reports of spontaneous puberty Males – DSD with incomplete virilisation
Congenital lipoid hyperplasia (StAR deficiency) (122, 123)	Classic 46,XY – deficient fetal testicular steroidogenesis, phenotypically female external genitalia 46,XX – anovulatory cycles and development of ovarian cysts Non-classic Variable gonadal function reported
3β-HSD2 deficiency (124)	Infertility is usually seen in both 46,XX and 46,XY affected individuals. 46,XX typically have androgen excess
P450 oxidoreductase deficiency (PORD) (125)	Of reported cases, DSD present in 78% of females (46,XX) and 60% of males (46,XY) Ovarian cysts in 39%

DSD, disorder of sexual development; HPG, hypothalamic–pituitary–gonadal axis; HSD, hydroxysteroid dehydrogenase; LH, luteinising hormone; TART, testicular adrenal rest tumour.