title: Supra-physiological rhGH administration induces gender-related differences in the hypothalamus-pituitary-thyroid (HPT) axis in healthy individuals.
abstract: OBJECTIVE
  The use of recombinant human growth hormone (rhGH) is a common habit among athletes. While the effects of rhGH administration have been described with contrasting results in males, no data exist in females to date. The aim of the present study was to evaluate the effects of rhGH administration on TSH, FT4and FT3levels and the time requested to return to baseline values after treatment withdrawal.
  
  
  METHODS
  Twenty-one healthy trained male and female athletes were treated with 0.03 mg rhGH/kg body mass 6 days/week for 3 weeks. We collected blood samples immediately before the first daily rhGH administration, at 3, 4, 8, 15 and 21 days of treatment and at 3 and 9 days after rhGH withdrawal.
  
  
  RESULTS
  In males, rhGH administration induced a significant (p < 0.01) early and stable TSH decrease and IGF-I increase, and a delayed FT4reduction without FT3modification, suggesting a central regulatory mechanism. In females, rhGH administration induced a significant (p < 0.01) early and transient TSH decrease and IGF-I increase, and a transient reduction in FT4without any changes in FT3concentrations. rhGH withdrawal was associated with a prompt normalization of TSH and FT4levels in males, while in females the effects of rhGH treatment had already disappeared during the last period of treatment.
  
  
  CONCLUSIONS
  We suggest that rhGH inhibits TSH at central level both in males and females. The pattern of normalization was different in the two genders probably due to gonadal steroids modulation on GH-IGF-I axis.
authors.affiliation: Unit of Endocrinology, Department of Motor, Human and Health Sciences, University of Rome "Foro Italico", Piazza Lauro de Bosis, 15, 00135, Rome, Italy. paolo.sgro@uniroma4.it.
authors.forename: P
authors.initials: P
authors.lastname: Sgrò
authors.affiliation: Department of Experimental Medicine, "Sapienza" University of Rome, Viale Regina Elena 324, 00161, Rome, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Sansone
authors.affiliation: Unit of Sports Medicine, Department of Motor, Human and Health Sciences, University of Rome "Foro Italico" , Piazza Lauro de Bosis, 15, 00135, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Parisi
authors.affiliation: Experimental Laboratory for Auxo-endocrinological Research, Istituto Auxologico Italiano, Via Ariosto, 13, 20145, Milan, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sartorio
authors.affiliation: Department of Experimental Medicine, "Sapienza" University of Rome, Viale Regina Elena 324, 00161, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Sansone
authors.affiliation: Department of Experimental Medicine, "Sapienza" University of Rome, Viale Regina Elena 324, 00161, Rome, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Romanelli
authors.affiliation: Department of Experimental Medicine, "Sapienza" University of Rome, Viale Regina Elena 324, 00161, Rome, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Lenzi
authors.affiliation: Unit of Endocrinology, Department of Motor, Human and Health Sciences, University of Rome "Foro Italico", Piazza Lauro de Bosis, 15, 00135, Rome, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Di Luigi
mesh_terms: D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000097:blood; D005260:Female; D019382:Human Growth Hormone / Q000008:administration & dosage* / Q000494:pharmacology*; D006801:Humans; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis; D008297:Male; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D012737:Sex Factors; D013961:Thyroid Gland / Q000187:drug effects / Q000378:metabolism*; D013972:Thyrotropin / Q000097:blood; D013974:Thyroxine / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D019382:Human Growth Hormone; D007334:Insulin-Like Growth Factor I; D013972:Thyrotropin; D013974:Thyroxine
keywords: Doping; FT4; IGF-I; Recombinant human growth hormone; TSH