Differential expression and interaction of melatonin and thyroid hormone receptors with estrogen receptor α improve ovarian functions in letrozole-induced rat polycystic ovary syndrome

Fil: Ghosh, Hindole. Kalinga University. Department of Zoology; India Fil: Rai, Seema. Guru Ghasidas Vishwavidyalaya. Department of Zoology; India Fil: Manzar, Md Dilshad. Majmaah University. College of Applied Medical Sciences. Department of Nursing; Arabia Saudita Fil: Pandi Perumal, Seithikurippu R. Saveetha University. Saveetha Institute of Medical and Technical Sciences. Saveetha Medical College and Hospitals; India Fil: Brown, Gregory M. University of Toronto. Centre for Addiction and Mental Health. Department of Psychiatry; Canada Fil: Reiter, Russel J. University of Texas. Health Science Center at San Antonio. Department of Cell Systems and Anatomy, Estados Unidos Fil: Cardinali, Daniel Pedro. Pontificia Universidad Católica Argentina. Facultad de Ciencias Médicas. Instituto de Investigaciones Biomédicas; Argentina Abstract: The objective of the present study was to investigate the effect of melatonin and L-thyroxine (T4) on the expression of various receptors, and some metabolic, reproductive, and gonadotropic hormones in letrozole-induced polycystic ovary syndrome (PCOS) in rats. - Material and methods: Assessment of gravimetric, hormonal profile and thyroid histology and relative expression of melatonin receptors (MT1, MT2) and estrogen receptor α (Erα) in thyroid and ovary, and type II iodothyronine deiodinase (Dio2) and thyroid hormone receptor α (TRα) in the ovary were performed using standard protocols. - Key findings: A significant increase in thyroid follicles numbers was noted in the hyperthyroid rat. T4 treatment to PCOS showed the expected increment in the circulating level of triiodothyronine (T3) and T4. Melatonin and T4 treatment of PCOS rats resulted in a significant decrease in the circulating level of T3 and T4. Hyperthyroid rats showed a decrement in plasma melatonin levels. However, T4 treatment to PCOS rats showed increased circulating melatonin levels, and a decrease in the circulating level of gonadotropins (LH and FSH), and testosterone. Melatonin treatment to PCOS-hyperthyroid rats resulted in the normal expression of ovarian and thyroid MT1 and ERα, receptors, which had been altered in PCOS and hyperthyroid rats, without any significant change in the MT2 receptor. - Significance: The present findings suggest a fine interplay and cross-talk via melatonin and its two receptors with ERα, TRα, and Dio2in thyroid and ovarian tissue during PCOS and hyperthyroidism pathogenicity.