Genomic coordinate 9:96,235,306
Here I present: “Male Pseudohermaphroditism Gynecomastia“, Victor McKusick, Mendelian Inheritance in Man’, 1966. (HSD17B3) 男性假兩性畸形乳房發育症。 icd10=Q56.1
INTRODUCTION.
Male pseudohermaphroditism gynecomastia refers to individuals with a 46,XY karyotype and testes, but with ambiguous external genitalia due to impaired androgen. Gynecomastia can appear in several specific conditions within this category.
There is evidence that male pseudohermaphroditism gynecomastia is caused by mutation in the enzyme 17-beta-hydroxysteroid dehydrogenase (HSD17B3) gene encoded on cytogenetic location 9q22.32 and genomic coordinate 9:96,235,306. The enzyme 17-beta-hydroxysteroid dehydrogenase (Enzyme Commission number #EC 1.1.1.62) converts androstenedione to testosterone in the fetal testes.
HSD17B3 deficiency is an autosomal recessive disorder that manifests, in males, as undermasculinization characterized by hypoplastic-to-normal internal genitalia (epididymis, vas deferens, seminal vesicles, and ejaculatory ducts) but female external genitalia and the absence of a prostate. This phenotype is caused by inadequate testicular synthesis of testosterone, which, in turn, results in insufficient formation of dihydrotestosterone in the anlage of the external genitalia and prostate during fetal development. At the expected time of puberty, there is a marked increase in plasma leuteinizing hormone and, consequently, in testicular secretion of androstenedione. Hence, a diagnostic hallmark of this disorder is a decreased plasma testosterone-to-androstenedione ratio. Significant amounts of the circulating androstenedione are, however, converted to testosterone, in peripheral tissues, thereby causing virilization.
