The Thyroid Axis, Prolactin and Exercise in Humans

Abstract The thyroid hormones thyroxine and triiodothyronine as well as the anterior pituitary hormone prolactin each serve vital roles in humans. When challenged by stressful situations, all of these hormones respond in an attempt to maintain homeostasis. One powerful stressor to invoke the release of these hormones is physical activity, that is, exercise. The thyroids and prolactin each have independent roles allowing the body to accommodate to exercise. But they also share an interrelation in their responses. Hypothalamic thyrotropin-releasing hormone release invoked by stress stimulates the release of thyroid-stimulating hormone and thus the thyroids as well as the release of prolactin. Likewise, estrogen serves as an inter-connective regulatory link by stimulating the release of both the thyroids and prolactin. The roles of these hormones in exercise are multifaceted, but one overlapping and common function is their combined aid and support of the tissue inflammatory responses after exercise. This is highly critical for facilitating elements of the adaptive-recovery procedures to exercise and exercise training.