Reduced peripheral thyroid hormone action in Turner Syndrome patients under growth hormone therapy

SUSPERREGUY S; MIRAS MB; MONTESINOS MM; MASCANFRONI ID; MUÑOZ L; SOBRERO G; SILVANO L; MASINI-REPISO AM; PELLIZAS CG

Viña del Mar, Chile

Congreso; XVIII Annual Meeting of the Latinoamerican Pediatric Endocrinology Society (SLEP); 2006

Sociedad latinoamericana de Endocrinología Pediátrica

Introduction and objectives: we reported that GH and IGF-I reduced TH action in rat tissues by lessening TH receptor (TR) expression. In TS, GH therapy improves adult height although the response is below the registered in other growth disorders. High GH doses are used in TS and supraphysiological IGF-I serum concentrations attained. Since somatic growth depends on TH status, a lesser TH action in bone induced by high IGF-I levels may be involved in the reduced final height of TS patients. Considering bone is not a human available tissue, we aimed at assessing the effect of GH treatment to TS patients on peripheral TH action. We measured TR mRNA levels in peripheral blood mononuclear cells (PBMC) and serum markers of TH action: thyrotropin (TSH), osteocalcin (OC), ß crosslaps (ßCL) and sex hormone binding globulin (SHBG) levels. Methodology: Ten normal, 10 TS and 10 TS under GH treatment (recombinant GH from mammalian or E. Coli cells, for at least 6 months, 0.33 mg/kg/week) were enrolled (5-14 y/o, prepuberal girls). Total RNA from PBMC was extracted (ficoll-hypaque) and TR mRNAs semi-quantified (in parallel to the ß-actin ) by RT-PCR. Serum TSH, OC, ßCL and SHBG were measured by EQLIA (Roche Elecsys 2010). Results: 1) TR mRNAs from PBMC were similar between normal and TS, but they were significantly reduced in TS-GH treated vs. TS; 2) GH therapy increased TSH, OC and ßCL, and reduced SHBG levels. Conclusions: GH reduced TRs from PBMC and some serum markers of TH action in TS patients. This effect would also take place at bone level and may be one of the factors involved in the reduced final height attained in GH-treated TS.