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Pathology

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Genetics

Question
4 out of 9
 

An XX infant is found to have external male genitalia and internal female genitalia. Physical examination reveals decreased BP, while laboratory examination reveals a serum sodium level of 132 meq/L. Additionally, bilateral adrenal cortical hyperplasia is present. A deficiency of which of the following enzymes is most likely to produce the clinical findings in this infants? (AIPG 2010)



A 3-β-dehydrogenase
B 11-hydroxylase

C 17-hydroxylase
D 21-hydroxylase

Ans. D 21-hydroxylase

a. Congenital adrenal hyperplasia (CAH) is a syndrome that results from a defect in the synthesis of cortisol.

b. This leads to excess ACTH secretion by the anterior Pituitary and resultant adrenal hyperplasia.

c. The defect in the synthesis of cortisol is the result of a deficiency in one of the enzymes in the normal pathway of cortisol synthesis, such as 21 or 11-hydroxylase.

d. Most cases of CAH result from a deficiency of 21-hydroxylase.

e. There is increased formation of 17-hydroxyprogesterone, which is then shunted into the production of testosterone.

f. This may cause virilism (pseudohermaphroditism) in female infants. That is, XX females with CAH develop ovaries, female ductal structure, and external male genitalia.

Genetics Flashcard List

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