Q.89. Which ONE of the following is the precursor molecule for corticosteroids?
(A) Androgen
(B) Estrogen
(C) Pregnenolone
(D) Mineralocorticoids

Pregnenolone serves as the key precursor for corticosteroids in steroidogenesis pathways. This multiple-choice question tests understanding of adrenal hormone biosynthesis.

Correct Answer

The correct option is (C) Pregnenolone.​

Pregnenolone forms directly from cholesterol via the enzyme CYP11A1 in adrenal mitochondria. It then branches into glucocorticoids like cortisol and mineralocorticoids like aldosterone through zona fasciculata and glomerulosa pathways.​

Option Explanations

• (A) Androgen: Androgens such as testosterone derive from pregnenolone via DHEA in the delta-5 or delta-4 pathways, positioning them as downstream products, not precursors, of corticosteroids.​

• (B) Estrogen: Estrogens like estradiol arise from androgen aromatization, making them end-products in gonadal tissues rather than precursors for adrenal corticosteroids.​

• (C) Pregnenolone: This molecule acts as the universal precursor for all steroids, including corticosteroids, after cholesterol side-chain cleavage.​

• (D) Mineralocorticoids: Mineralocorticoids like aldosterone represent final corticosteroids derived from pregnenolone via progesterone and DOC, so they cannot precede themselves.​

Steroidogenesis Pathway Overview

Cholesterol converts to pregnenolone in adrenal cortex mitochondria. Pregnenolone undergoes hydroxylation and cleavage: 17α-hydroxy pathway leads to cortisol, while the plain progesterone path yields aldosterone.​