Background: Sex steroids probably stimulate growth-hormone secretion during puberty, which in turn contributes to the development of gender specific body characteristics. Hypothetically, adequate growth hormone levels in transgender persons are also important to achieve the best therapeutic results. The influence of cross-sex hormone treatment (CHT) at growth-hormone production in adult transgender persons is not yet elucidated.
Objective: To investigate the influence of CHT on growth-hormone production by the determination insulin-like growth factor (IGF-1) levels.
Methods: This prospective study includes 89 transgender persons, 43 male-to-female individuals (MtFs) and 46 FtMs (age ≥18) who started with CHT between March 2015 and December 2015. MtFs were treated with cyproterone acetate in combination with estradiol transdermally or orally. FtMs were treated with testosterone transdermally or intramuscular. Serum IGF-1 and IGF binding protein 3 (IGFBP-3) levels were determined at baseline and after three of CHT. IGFBP-3 was determined to calculate the IGF-1/IGFBP-3 ratio to estimate the availability of free IGF-1. IGF-1 was measured using an automated immunoassay (Liaison, DiaSorin) and IGFBP-3 using an ELISA (DRG).
Results: In MtFs mean IGF-1 levels increased from 31 nmol/L to 36 nmol/L (16%, 95CI: 11% to 20%) between baseline and three months of CHT and the mean IGF-1/IGFBP-3 ratio with 25% (95CI: 17% to 32%). At baseline two MtFs had elevated IGF-1 levels (i.e. levels above the upper limit of their age-specific reference range), which increased to 14 MtFs after three months of CHT. In FtMs mean IGF-1 levels increased from 39 nmol/L to 43 nmol/L (10%, 95CI: 6% to 15%) and mean IGF-1/IGFBP-3 ratio with 28% (95CI: 21% to 37%). The number of FtMs with elevated IGF-1 levels increased from nine at baseline to 19 after three months of CHT.
Conclusions: In both MtFs and FtMs IGF-1 levels increased moderately during the first three months of CHT.