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Androgen insensitivity syndrome
Hypospadias and epispadias
Benign prostatic hyperplasia
Male hypoactive sexual desire disorder
Premature ovarian failure
Polycystic ovary syndrome
Sex cord-gonadal stromal tumor
Surface epithelial-stromal tumor
Germ cell ovarian tumor
Pelvic inflammatory disease
Female sexual interest and arousal disorder
Genito-pelvic pain and penetration disorder
Fibrocystic breast changes
Paget disease of the breast
Preeclampsia & eclampsia
Intrauterine growth restriction
Congenital cytomegalovirus (NORD)
Neonatal herpes simplex
Congenital rubella syndrome
Gestational trophoblastic disease
Fetal hydantoin syndrome
Fetal alcohol syndrome
Disorders of sex chromosomes: Pathology review
Disorders of sexual development and sex hormones: Pathology review
Sexually transmitted infections: Vaginitis and cervicitis: Pathology review
Sexually transmitted infections: Warts and ulcers: Pathology review
HIV and AIDS: Pathology review
Penile conditions: Pathology review
Testicular and scrotal conditions: Pathology review
Prostate disorders and cancer: Pathology review
Testicular tumors: Pathology review
Uterine disorders: Pathology review
Ovarian cysts and tumors: Pathology review
Cervical cancer: Pathology review
Vaginal and vulvar disorders: Pathology review
Benign breast conditions: Pathology review
Breast cancer: Pathology review
Complications during pregnancy: Pathology review
Congenital TORCH infections: Pathology review
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Antonia Syrnioti, MD
Brittany Norton, MFA
Tanner Marshall, MS
5α- reductase deficiency is a genetic disorder in which a protein called 5α reductase is defective or absent.
That’s an enzyme that converts the male hormone testosterone to its more potent form, called dihydrotestosterone.
One of the most important roles of dihydrotestosterone is to help male external genitalia develop in a male fetus.
Okay, normally, very early on in fetal life, male and female internal sex organs and external genitalia are undifferentiated and look identical.
Within the first few months of development, testes develop in the male fetus.
The testes start producing testosterone - a male steroid hormone that belongs to a class of hormones called androgens.
The testosterone gets released into the blood and a tiny fraction of it gets converted by 5α- reductase, which is mainly made in the skin of the genital area, into dihydrotestosterone.
Over time, dihydrotestosterone levels start rising and it affects undifferentiated genital structures.
Looking closely at these structures, at the top there’s the genital tubercle, which is a small projection.
Just below that, there's the urethral groove, which is the external opening of the urogenital sinus or the future urethra and bladder and is surrounded by the urethral folds and the labioscrotal swellings.
Now, once dihydrotestosterone reaches these structures, it makes the genital tubercle elongate into the phallus which will eventually be the penis.
The elongating genital tubercle pulls up the urethral folds which fuse in the midline, forming the spongy or penile urethra.
The tips of the urethral folds remain unfused and that forms the external urethral opening at the distal tip of the penis.
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