Context: An interaction between ghrelin, which is implicated in the regulation of short- and long-term energy balance, and thyroid function has been reported in hyperthyroidism where ghrelin levels are reversibly suppressed. We measured serum ghrelin levels and metabolic indices in hypothyroid patients before and after L-thyroxin replacement.

Patients and methods: Eleven patients were examined twice: 1) in the hypothyroid state, and 2) after at least 2 months of euthyroidism. Ten healthy subjects served as a control group. Ghrelin was measured in conjunction with indirect calorimetry and a hyperinsulinemic euglycemic clamp.

Results: Serum ghrelin levels were increased by 32% under basal conditions in the hypothyroid state (PRE) as compared to post treatment (POST) (pg/ml): 976.4 ± 80.8 vs. 736.8 ± 67.1 (p < 0.001). This difference prevailed during the clamp but a decline was observed in both states: 641.4 ± 82.2 vs. 444.3 ± 66.8 µg/ml (p = 0.005). The hypothyroid state was associated with decreased resting energy expenditure, increased respiratory quotient and insulin resistance. Serum ghrelin levels as well as the metabolic aberrations became normalized after L-thyroxin replacement as compared to the control subjects.

Conclusion: serum ghrelin levels are reversibly increased in hypothyroid patients. It remains to be investigated whether this represents a direct effect of iodothyronines on ghrelin secretion or clearance, or a compensatory response to the abnormal energy metabolism in hypothyroid patients.