Leptin is a 16-kDa adipokine that regulates energy homeostasis. In diet-induced obesity in humans, serum leptin levels are typically:

• A High, with resistance to leptin signaling at the hypothalamus ✓
• B Low, indicating leptin deficiency
• C Normal, unaffected by adiposity
• D Absent, due to suppression by hyperinsulinemia

Explanation

In most common human obesity, leptin is produced proportionally to adipose mass and serum levels are markedly elevated. However, the hypothalamus exhibits leptin resistance due to: (1) impaired leptin transport across the blood-brain barrier (reduced leptin receptor in choroid plexus), (2) downregulation of long-form leptin receptor (Ob-Rb) signaling, and (3) SOCS3 upregulation inhibiting JAK2/STAT3 pathway. True leptin deficiency (Ob/Ob-equivalent) is rare in humans and presents as severe early-onset obesity with hypogonadism.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.