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Leptin and the pituitary-thyroid axis: a comparative study in lean, obese, hypothyroid and hyperthyroid subjects
J H Pinkney1, S J Goodrick, J Katz
1University of Bristol, Department of Medicine, Bristol Royal Infirmary, UK.
Clinical Endocrinology
|April 10, 1999
Summary
Plasma leptin levels are elevated in hypothyroidism and correlate with thyroid function and body fat. Treatment for hypothyroidism reduces leptin levels, suggesting a reversible interaction between leptin and the pituitary-thyroid axis.
Area of Science:
- Endocrinology
- Metabolic Research
- Hormone Interactions
Background:
- Leptin, a key regulator of energy balance, and the pituitary-thyroid axis are crucial for metabolic homeostasis.
- Understanding their interplay is essential for elucidating metabolic and endocrine disorders.
Purpose of the Study:
- To investigate the relationship between plasma leptin levels and thyroid hormone status in euthyroid, hyperthyroid, and hypothyroid individuals.
- To explore the impact of obesity on leptin and thyroid hormone interactions.
- To assess the effect of hypothyroidism treatment on plasma leptin concentrations.
Main Methods:
- Cross-sectional study involving euthyroid (lean and obese), hyperthyroid, and hypothyroid patients.
- Measurement of plasma leptin, free thyroid hormones (T3), and thyroid-stimulating hormone (TSH).
- Longitudinal assessment of hypothyroid patients during thyroxine replacement therapy.
Main Results:
- Plasma leptin was significantly elevated in obese euthyroid and untreated hypothyroid subjects compared to lean euthyroid and hyperthyroid subjects.
- In obese euthyroid individuals, TSH levels correlated positively with body fat percentage and plasma leptin.
- Treatment of hypothyroidism with thyroxine led to a significant decrease in plasma leptin levels.
Conclusions:
- Leptin and the pituitary-thyroid axis interact in euthyroid states, with both positively correlating with adiposity.
- Hypothyroidism is associated with reversible increases in plasma leptin concentrations.
- These findings support a bidirectional relationship between leptin and thyroid function.