Thyroid hormones and the interrelationship of cortisol and prolactin: influence of prolonged, exhaustive exercise Hormony tarczycy a wzajemne relacje między stężeniem kortyzolu i prolaktyny: wpływ długotrwałego, wyczerpującego wysiłku fizycznego

Background: This study examined how prolonged, exhaustive exercise affects: (1) thyroid hormones, and (2) the interrelationship of cortisol and prolactin responses to such exercise on thyroid hormones. Material and methods: Male subjects performed a treadmill run at their individual ventilatory threshold until exhaustion. Blood samples were taken before exercise at rest, baseline (BL), at exhaustion (EXH), 30-60-90-minutes into recovery (30 mR, 60 mR, 90 mR), and 24-hours into recovery from exercise (24 hR). Blood was analyzed for free T3 (fT3), free T4 (fT4), thyroid-stimulating hormone (TSH), cortisol and prolactin. Results: ANOVA analysis revealed that at EXH all hormones were increased (p < 0.01) from BL levels. At 30 mR and 60 mR the thyroid hormones had decreased and returned to BL levels; however, cortisol and prolactin remained significantly increased (p < 0.05). At 90 mR all hormones were not different from BL levels. By 24 hR, cortisol, fT3 and TSH were decreased from BL (p < 0.05). Correlations revealed EXH cortisol responses were related to the 24 hR TSH responses (rs = –0.69, p < 0.01). In addition, EXH cortisol and 24 hR fT3 responses were related (rs = –0.51, p < 0.02). Furthermore, the EXH prolactin and TSH responses were related (rs = +0.56, p < 0.01), and the 30 mR prolactin responses were related to the EXH TSH responses (rs = +0.43, p < 0.05). Conclusions: Exhaustive exercise; (1) decreases select thyroid hormones by 24 hours into recovery, (2) cortisol responses are inversely related to these thyroid reductions, and (3) prolactin responses (increases) are directly related to TSH changes. (Pol J Endocrinol 2009; 60 (4): 252–257)