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Isolated 17,20-lyase deficiency
Isolated 17,20-lyase deficiency (ILD), also called isolated 17,20-desmolase deficiency, is a rare endocrine and autosomal recessive genetic disorder which is characterized by a complete or partial loss of 17,20-lyase activity and, in turn, impaired production of the androgen and estrogen sex steroids. The condition manifests itself as pseudohermaphroditism (partially or fully underdeveloped genitalia) in males, in whom it is considered to be a form of intersex, and, in both sexes, as a reduced or absent puberty/lack of development of secondary sexual characteristics, resulting in a somewhat childlike appearance in adulthood (if left untreated).〔(【引用サイトリンク】 Chapter 11 – 46,XY Disorders of Sexual Development )〕
Unlike the case of combined 17α-hydroxylase/17,20-lyase deficiency, isolated 17,20-lyase deficiency does not affect glucocorticoid production (or mineralocorticoid levels), and for that reason, does not result in adrenal hyperplasia or hypertension.〔〔
==Cause==
Isolated 17,20-lyase deficiency is caused by genetic mutations in the gene ''CYP17A1'', which encodes for 17,20-lyase, while not affecting 17α-hydroxylase, which is encoded by the same gene.〔〔
Observed physiological abnormalities of the condition include markedly elevated serum levels of progestogens such as progesterone and 17-hydroxyprogesterone (due to upregulation of precursor availability for androgen and estrogen synthesis), very low or fully absent peripheral concentrations of androgens such as dehydroepiandrosterone (DHEA), androstenedione, and testosterone and estrogens such as estradiol (due to the lack of 17,20-lyase activity, which is essential for their production), and high serum concentrations of the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone (LH) (due to a lack of negative feedback on account of the lack of sex hormones).
抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』
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