title: Thyroid hormone and estrogen regulate exercise-induced growth hormone release.
abstract: Growth hormone (GH) regulates whole body metabolism, and physical exercise is the most potent stimulus to induce its secretion in humans. The mechanisms underlying GH secretion after exercise remain to be defined. The aim of this study was to elucidate the role of estrogen and pituitary type 1 deiodinase (D1) activation on exercise-induced GH secretion. Ten days after bilateral ovariectomy, animals were submitted to 20 min of treadmill exercise at 75% of maximum aerobic capacity and tissues were harvested immediately or 30 min after exercise. Non-exercised animals were used as controls. A significant increase in D1 activity occurred immediately after exercise (~60%) in sham-operated animals and GH was higher (~6-fold) 30 min after exercise. Estrogen deficient rats exhibited basal levels of GH and D1 activity comparable to those found in control rats. However, after exercise both D1 activity and serum GH levels were blunted compared to sedentary rats. To understand the potential cause-effect of D1 activation in exercise-induced GH release, we pharmacologically blocked D1 activity by propylthiouracil (PTU) injection into intact rats and submitted them to the acute exercise session. D1 inhibition blocked exercise-induced GH secretion, although basal levels were unaltered. In conclusion, estrogen deficiency impairs the induction of thyroid hormone activating enzyme D1 in the pituitary, and GH release by acute exercise. Also, acute D1 activation is essential for exercise-induced GH response.
authors: Institute of Biophysics Carlos Chagas Filho and School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Daniele Leão
authors: DL
authors: Ignacio
authors: Institute of Biophysics Carlos Chagas Filho and School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Diego H
authors: DH
authors: da S Silvestre
authors: Institute of Biophysics Carlos Chagas Filho and School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: João Paulo Albuquerque
authors: JP
authors: Cavalcanti-de-Albuquerque
authors: Institute of Biophysics Carlos Chagas Filho and School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Ruy Andrade
authors: RA
authors: Louzada
authors: Institute of Biophysics Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors: Denise P
authors: DP
authors: Carvalho
authors: Institute of Biophysics Carlos Chagas Filho and School of Physical Education and Sports, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil; Department of Endocrinology and Metabolism, Rush University Medical Center, Chicago, Illinois, United States of America.
authors: João Pedro
authors: JP
authors: Werneck-de-Castro
mesh_terms: D000818:Animals; D004967:Estrogens / Q000378:metabolism*; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D007453:Iodide Peroxidase / Q000037:antagonists & inhibitors / Q000378:metabolism*; D010805:Physical Conditioning, Animal; D010902:Pituitary Gland / Q000378:metabolism; D011441:Propylthiouracil / Q000008:administration & dosage; D051381:Rats; D013963:Thyroid Hormones / Q000378:metabolism*
chemical_list: D004967:Estrogens; D013963:Thyroid Hormones; D011441:Propylthiouracil; D013006:Growth Hormone; D007453:Iodide Peroxidase