Male pseudohermaphroditism due to 17-beta-hydroxysteroid dehydrogenase deficiency

Male pseudohermaphroditism due to 17-beta-hydroxysteroid dehydrogenase deficiency is a deficiency of 17-beta-hydroxysteroid dehydrogenase isozyme 3 which leads to male pseudohermaphroditism, a condition characterized by incomplete differentiation of male genitalia in 46XY males. It is caused by mutations in the HSD17B3 gene.

Etiology
17-beta-hydroxysteroid dehydrogenase deficiency type 3 (17βHSD3) is a disorder in testosterone biosynthesis. As a consequence of this disorder, normal male sexual differentiation in impaired and hypovirilization occurs (less male sexual characteristics).

Clinical characteristics
17-beta-hydroxysteroid dehydrogenase deficiency-3 is clinically characterized by either ambiguous external genitalia or complete female external genitalia at birth as a consequence of impaired male sexual differentiation in 46,XY individuals. Further investigations on ambiguous genitalia will eventually lead to findings of intersexuality. Severe hypovirilization (absence of male differentiation) can lead to development of female external genitalia. These females (!) are often discovered when there is absence of menarche (first menstruation) and when they begin to virilize during puberty (slowly become more like a man; deepening of the voice, acne, male musculature etc). At careful examination, testis can often be found in the inguinal channel.

Biochemically
17-beta-hydroxysteroid dehydrogenase deficiency-3 is biochemically characterized by decreased levels of testosterone and increased levels of androstenedione as a result of the defect in conversion of androstenedione into testosterone. This leads to clinically important higher ratio of androstenedione to testosterone (A'dion/T).-

Genetics
17-beta-hydroxysteroid dehydrogenase deficiency-3 is caused by gene mutations found in the 17BHSD3 gene. 17-beta-hydroxysteroid dehydrogenase deficiency-3 is an autosomal recessive disorder.