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Leptin Concentrations, Sex Hormones, and Cortisol in Nondiabetic Men—Authors’ Response

University of Texas Health Sciences Center San Antonio, Texas 78284

P. Karhapää, L. Mykkänen and M. Laakso

Kuopio University Hospital Kuopio, Finland

Thanks to Dr. J. Licinio for his letter on our report (1). We are, of course, well aware that leptin levels have a diurnal variation. We have previously published that leptin levels vary diurnally in diabetic subjects (2) and that glibenclamide (but not acarbose) raises leptin concentrations. In that report we cited the report of Sinha et al. (2) but were not aware of your report of Licinio et al. (3). We did, however, cite evidence (4, 5) for the circadian rhythm of cortisol in our report as one of the explanations for the circadian variation in leptin (2). So we are certainly not unaware of the circadian rhythm of leptin and indeed cortisol.

We were surprised by the letter as our report treats almost exclusively the observation that sex hormones are unlikely to explain the sex difference in leptin levels. We acknowledge that repeated sampling may improve precision for both sex hormones and cortisol, but our correlations of both sex hormones and cortisol with obesity (i.e. BMI) are in the range previously reported for studies that used multiple sampling. So we stand by the precision of our laboratory measurements. We admire both the financial resources of the investigators and the fortitude of the 6 subjects to have 1242 measurements made. We acknowledge that leptin is involved in cortisol release, although we suspect that the association of leptin with cortisol is much weaker than its relation to adiposity; thus, carefully controlled pharmacologic studies or very frequent sampling (as were done by Licinio et al. (2)) are necessary to elucidate this association.

Footnotes

Address correspondence to: Steven M. Haffner, Department of Internal Medicine, University of Texas Health Sciences Center, 7703 Floyd Curl Drive, San Antonio, Texas 78284-7873.

Received November 20, 1997.

References

1. Haffner SM, Miettinen H, Karhapää P, Mykkänen L, Laakso M. 1997 Leptin concentrations, sex hormones, and cortisol in nondiabetic men. J Clin Endocrinol Metab. 82:1807–1809.[Abstract/Free Full Text]
2. Haffner SM, Hanefeld M, Fischer S, Fücker K, Leonhart W. 1997 Glibenclamide, but not acarbose, increases leptin concentrations parallel to changes in insulin in subjects with NIDDM. Diabetes Care. 20:1430–1434.[Abstract]
3. Licinio J, Mantzoros C, Negrão AB, et al. 1997 Human leptin levels are pulsatile and inversely related to pituitary-adrenal function. Nat Med. 3:575–579.[CrossRef][Medline]
4. Weitzman ED, Zimmerman JC, Czeisler CA, Ronda JM. 1983 Cortisol secretion is inhibited during sleep in normal man. J Clin Endocrinol Metab. 56:352–358.[Abstract/Free Full Text]
5. Lejeune-Lenain C, Van Cauter E, Desir D, Beyloos M, Franckson JRM. 1987 Control of circadian and episodic variations of adrenal androgens secretion in man. J Endocrinol Invest. 10:267–276.[Medline]

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