Gonadotropin Decrease Induced by Prolonged Exercise at About 55% of the V̇O₂max in Different Phases of the Menstrual Cycle

Abstract

In order to evaluate the influence of physical exercise on the hypothalamic-pituitary-ovarian axis, we studied ten women in the early follicular phase (EFP), twelve in the late follicular phase (LEP) and nine in the luteal phase (LP). The test consisted of a 90-minutc physical exercise on a motor driven treadmill at 55 60% of V̇O₂max. Blood samples were taken before, during and after the test. Prolactin and Cortisol did not increase in any phase. Estradiol showed a significant increase in LFP (from 361.5±110.6 to 472.7±138.9 pmol/L) and in LP (from 457.2±94.6 to 555.3±96.9 pmol/L) but not in EFP. Progesterone levels increased significantly only in LP (from 28.2±6.7 to 33.5±6.7 mmol/L): Luteinizing hormone (LH) levels decreased significantly in all phases: from 13.7±2.0 to 10.5±1.1 IU/L in EFP; from 14.6±2.1 to 11.5±1.9 IU/L in LFP and from 7.5±1.3 to 5.7±1.0 IU/L in LP, while follicle stimulating hormone (FSH) levels decreased only in LFP (from 8.1+0.5 to 6.7±0.6 IU/L). Our exercise protocol (prolonged, continous and moderate) was able to cause a decrease in gonadotropins levels, and this phenomenon is not due to changes in the other tested hormones.

Key words

Gonadotropins - estradiol - progesterone - prolactin - Cortisol - menstrual cycle - physical exercise