Defective CYP17A1 causes AH5

Steroid 17-alpha-hydroxylase/17,20 lyase (CYP17A1) mediates both 17-alpha-hydroxylase and 17,20-lyase activity, allowing the adrenal glands and gonads to synthesise both 17-alpha-hydroxylated glucocorticoids and sex steroids respectively (Kagimoto et al. 1998). Defects in CYP17A1 can cause Adrenal hyperplasia 5 (AH5), a form of congenital adrenal hyperplasia (CAH), a common recessive disease due to defective synthesis of cortisol and sex steroids. Common symptoms include mild hypocortisolism, ambiguous genitalia in genetic males or failure of the ovaries to function at puberty in genetic females, metabolic alkalosis due to hypokalemia and low-renin hypertension. CYP17A1 can have defects in either or both of 17-alpha-hydroxylase and 17,20-lyase activities thus patients can show combined partial 17-alpha-hydroxylase/17,20-lyase deficiency or isolated 17,20-lyase deficiency traits (Yanase et al. 1992, Kater & Biglieri 1994, Fluck & Miller 2006, Miller 2012).

类固醇17-α-羟化酶/17,20裂合酶（CYP17A1）介导17-α-羟化酶和17,20-裂合酶的活性，使得肾上腺和生殖腺分别合成17-α-羟化糖皮质激素和性激素（Kagimoto等，1998年）。CYP17A1的缺陷可导致肾上腺增生5型（AH5），一种先天性肾上腺增生（CAH）的形式，这是一种由于皮质醇和性激素合成缺陷而引起的常见隐性遗传疾病。常见症状包括轻度皮质醇缺乏、遗传男性外生殖器不明确或遗传女性在青春期卵巢功能不全，由于低钾血症和低肾素性高血压引起的代谢性碱中毒。CYP17A1的缺陷可能存在于17-α-羟化酶和17,20-裂合酶的任一或两者之中，因此患者可能表现出联合的17-α-羟化酶/17,20-裂合酶部分缺陷或孤立的17,20-裂合酶缺陷特征（Yanase等，1992年，Kater & Biglieri，1994年，Fluck & Miller，2006年，Miller，2012年）。