Isolated 17,20-lyase deficiency

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Isolated 17,20-lyase deficiency
Synonyms	17,20-desmolase deficiency
Pronounce	N/A
Specialty	N/A
Symptoms	Hypertension, ambiguous genitalia, hypogonadism
Complications	Infertility, adrenal hyperplasia
Onset	Congenital
Duration	Lifelong
Types	N/A
Causes	Mutations in the CYP17A1 gene
Risks	Family history of the condition
Diagnosis	Genetic testing, hormone level testing
Differential diagnosis	Congenital adrenal hyperplasia, androgen insensitivity syndrome
Prevention	N/A
Treatment	Hormone replacement therapy, surgery
Medication	Glucocorticoids, mineralocorticoids
Prognosis	Variable, depending on severity and treatment
Frequency	Rare
Deaths	N/A

Isolated 17,20-lyase deficiency is a rare congenital disorder that affects the production of sex steroids due to a defect in the enzyme 17,20-lyase. This enzyme is crucial for the biosynthesis of androgens and estrogens from progestogens.

Pathophysiology

The enzyme 17,20-lyase, also known as CYP17A1, is responsible for the conversion of pregnenolone and progesterone into their respective 17-hydroxylated products, which are then converted into dehydroepiandrosterone (DHEA) and androstenedione. In isolated 17,20-lyase deficiency, mutations in the CYP17A1 gene impair this conversion, leading to decreased levels of DHEA and androstenedione, and consequently, reduced synthesis of testosterone and estradiol.

Clinical Presentation

Patients with isolated 17,20-lyase deficiency typically present with ambiguous genitalia or disorder of sex development (DSD) in 46,XY individuals, due to insufficient androgen production. 46,XX individuals may present with delayed puberty, primary amenorrhea, and lack of secondary sexual characteristics.

Diagnosis

Diagnosis is based on clinical presentation, hormonal assays showing low levels of androgens and estrogens with elevated levels of gonadotropins, and genetic testing confirming mutations in the CYP17A1 gene.

Treatment

Management of isolated 17,20-lyase deficiency involves hormone replacement therapy to induce and maintain secondary sexual characteristics and to address any associated adrenal insufficiency. Glucocorticoids may be administered to suppress elevated adrenocorticotropic hormone (ACTH) levels.

See also

• Congenital adrenal hyperplasia
• Disorder of sex development
• CYP17A1
• Androgen
• Estrogen
• Hormone replacement therapy

See Also

• Endocrinology
• Genetic disorder
• Steroidogenesis

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