Table 1. Factors that regulate circulating leptin levels.
| Factors promoting leptin secretion |
|---|
| * Excess energy stored as fat (obesity) |
| * Overfeeding |
| Glucose |
| Insulin |
| Glucocorticoids |
| Estrogens‡ |
| Inflammatory cytokines, including Tumor Necrosis Factor-α and Interleukin-6 (acute effect) |
| Factors inhibiting leptin secretion |
| * Low energy states with decreased fat stores (leanness) |
| * Fasting |
| Catecholamines and adrenergic agonists |
| Thyroid hormones |
| Androgens ‡ |
| Peroxisome Proliferator-activated Receptor-γ (PPARγ) agonists† |
| Inflammatory cytokines, including Tumor Necrosis Factor-α (prolonged effect) |
*
Denotes major factor influencing leptin levels.
†
Unlike animals, in humans PPARγ agonists decrease leptin gene expression but increase subcutaneous fat mass. Thus, the net effect is null.