OBJECTIVE: The aim of this study was to investigate the messenger ribonucleic acid expression of leptin (L-mRNA) and the leptin receptor (OB-RmRNA) in subcutaneous fat tissue and to determine their relationship with leptin and testosterone and steroid serum levels over the course of the menstrual cycle (MC), in obese (OBW) and non-obese women (NOW). DESIGN: Observational study investigating mRNA transcript expression of leptin and the leptin receptor from human subcutaneous fat specimens, as

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... l as leptin serum levels, both in relation to the testosterone and sex hormones during the MC in obese and non-obese women. METHODS: Nineteen women, thirteen with a body mass index (BMI) ≥ 25 Kg/m 2 and 6 with BMI < 25 Kg/m 2 were included. RT-PCR was used to detect L-mRNA transcripts of leptin and its receptor in samples from 28 fat biopsies taken from seven volunteers (20 from OW and 8 from NOW). The serum concentrations of leptin and steroid hormones were measured throughout the MC using radioinmuno analysis. RESULTS: The percentages of women expressing leptin L-mRNA during the phases of the MC were: early follicular (EF), 14.3%; late follicular (LF), 28.6%; early luteal (EL), 14.3%; and late luteal (LL), 42.9%. The percentages of OB-RmRNA were: EF, 71.4%; LF, 14.3%; EL, 28.6%; and LL, 71.4%. Leptin serum levels were directly related to BMI (p < 0.001), and testosterone (p < 0.001) and indirectly to SHBG (p < 0.001). CONCLUSION: The L-mRNA expression and its receptor in subcutaneous human tissue are regulated throughout the MC in a periodic manner. The physiological role of testosterone in regulation of expression L-mRNA and OB-RmRNA during the secretory phase of the MC in obese women requires further investigation.