MCQ – 90225

Enzyme deficiency in congenital adrenal hyperplasia leading to the decreased synthesis of cortisol, aldosterone, and androstenedione is

Correct Answer » A Explanation

A. 3β-Hydroxysteroid dehydrogenase

• Correct answer according to the provided study material.
• Deficiency causes decreased synthesis of:
  • Cortisol
  • Aldosterone
  • Androgens, including reduced testosterone production; dehydroepiandrosterone (DHEA) may be increased due to the pathway abnormality.
• It can cause:
  • Salt-wasting crisis
  • Dehydration
  • Hyperkalemia
  • Under-virilization/ambiguous genitalia in males
  • Mild virilization in females because DHEA is a weak androgen.

B. 11β-Hydroxylase

• Incorrect.
• Causes decreased cortisol synthesis.
• However, mineralocorticoid activity is increased due to accumulation of 11-deoxycorticosterone (DOC).
• Causes:
  • Hypertension
  • Hypokalemia
  • Increased androgens
  • Virilization in females.

C. 17α-Hydroxylase

• Incorrect.
• Causes decreased:
  • Cortisol
  • Sex hormones/androgens
• Mineralocorticoid activity is increased because of accumulation of DOC.
• Therefore, patients typically have:
  • Hypertension
  • Hypokalemia
  • Failure of sexual development
  • Undervirilization in males.

D. 21-Hydroxylase

• Incorrect.
• This is the most common cause of congenital adrenal hyperplasia.
• Causes decreased:
  • Cortisol
  • Aldosterone
• However, androgen production is increased, not decreased.
• Excess androgens cause:
  • Virilization/ambiguous genitalia in 46,XX infants
  • Precocious puberty in males
• Therefore, it does not fit the question because androstenedione/androgen activity is increased.