Pro-opiomelanocortin (POMC) is cleaved differently in different pituitary cell types. In the anterior pituitary corticotroph, the principal products are:

• A ACTH, beta-lipotropin and beta-endorphin, with minimal MSH production ✓
• B Alpha-MSH and CLIP as the dominant products, with little ACTH
• C Melanotropins exclusively, because PC1 is absent from the pituitary
• D Beta-endorphin alone, since ACTH is produced only in the hypothalamus

Explanation

In anterior pituitary corticotrophs, prohormone convertase 1 cleaves POMC into ACTH, beta-lipotropin and beta-endorphin. In the intermediate lobe (prominent in rodents, rudimentary in humans), PC2 further cleaves ACTH to alpha-MSH and CLIP. Humans lack a functional intermediate lobe, so circulating MSH derives largely from ACTH cleavage elsewhere. Option B describes intermediate lobe processing, and ACTH is definitively a pituitary product, ruling out D.

Reference: Ganong's Review of Medical Physiology, 26th ed.

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Written and medically reviewed by the StethoPrep medical team.