title: Thyroid hormones and the interrelationship of cortisol and prolactin: influence of prolonged, exhaustive exercise.
abstract: 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.
  
  
  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 T(3) (fT(3)), free T(4) (fT(4)), 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, fT(3) 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 fT(3) responses were related (rs = -0.51, p < 0.02). Furthermore, the EXH prolactin and TSH responses were related (r(s) = +0.56, p < 0.01), and the 30 mR prolactin responses were related to the EXH TSH responses (r(s) = +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.
authors.affiliation: Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, NC 27599, USA. thackney@med.unc.edu
authors.forename: Anthony C
authors.initials: AC
authors.lastname: Hackney
authors.forename: Jennifer D
authors.initials: JD
authors.lastname: Dobridge
mesh_terms: D000328:Adult; D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D008297:Male; D010807:Physical Endurance / Q000502:physiology*; D011388:Prolactin / Q000097:blood*; D012016:Reference Values; D013963:Thyroid Hormones / Q000097:blood*; D013972:Thyrotropin / Q000097:blood; D055815:Young Adult
chemical_list: D013963:Thyroid Hormones; D011388:Prolactin; D013972:Thyrotropin; D006854:Hydrocortisone