Study summary · research use only
Discrepancy between serum leptin values and total body fat in response to the oral growth hormone secretagogue MK-677
Plain-language summary
Paraphrased from the published abstract below — not a verdict on whether anything works.
This randomized, double-blind, parallel human study examined the oral GH secretagogue MK-677's effects on serum leptin, thyroid hormones, and testosterone in obese males. Twenty-four obese males, 19-49 years of age, with body mass index over 30 kg/m2 and waist:hip ratio over 0.95, received MK-677 (25 mg/day; n = 12) or placebo (n = 12) for 8 weeks. The authors report MK-677 transiently increased serum leptin and leptin/body fat ratio at 2 weeks but not at 8 weeks, and increased free triiodothyronine at 8 weeks. Peak TSH was increased at 8 weeks but stayed within the normal range. LH and FSH peaks were similar to placebo, while total testosterone was reduced though the testosterone/SHBG ratio was unchanged. The authors state MK-677 affected circulating factors relevant to adipose tissue and fuel metabolism.
Abstract
Growth hormone (GH) treatment decreases total body fat while this effect has not yet been documented for the oral GH secretagogue MK-677. In the present study, the effects of MK-677 treatment on serum levels of leptin, thyroid hormones and testosterone were determined. This was a randomized, double-blind, and parallel study. Twenty-four healthy obese males, 19-49 years of age, with body mass index (BMI) > 30 kg/m2 and a waist:hip ratio > 0.95, were treated with MK-677 (25 mg/day; n = 12) or placebo (n = 12) for 8 weeks. MK-677 treatment increased serum leptin levels and leptin/body fat ratio at 2 weeks of treatment (P < 0.05 vs. placebo) but no significant change was observed at 8 weeks. An increase in serum free 3, 5, 3'-triiodothyronine (free T3) was not detected until 8 weeks of MK-677 treatment (P < 0.05 vs. placebo). Peak serum thyroid stimulating hormone (TSH) concentration after MK-677 administration was similar to that after placebo administration at initiation of treatment and at 2 weeks. At 8 weeks of MK-677 treatment, mean peak serum TSH concentration was increased (P < 0.05 vs. placebo) although it remained within the normal range. Serum peak values of luteinizing hormone (LH) and follicle stimulating hormone (FSH) were similar after MK-677 and placebo administration. MK-677 treatment reduced serum total testosterone (P < 0.05 vs. placebo) although total testosterone/sex hormone-binding globulin (SHBG) ratio (an index of free testosterone) was not changed. Treatment with the oral GH secretagogue MK-677 transiently increased serum leptin levels and leptin/body fat ratio at 2 weeks of treatment, and increased serum free T3 after 8 weeks. These results indicate that MK-677 treatment is able to affect circulating factors of importance for adipose tissue mass and fuel metabolism.
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