Abstract
Irisin (Ir) deficiency may be a contributing factor in metabolic disease. This study
aimed to investigate the effect of supraphysiological doses of recombinant human growth
hormone (rhGH) on Ir plasma concentration in relation to metabolic disorders, including
obesity and other components of metabolic syndrome. We studied 36 girls with Turner
syndrome (mean age 8.2 years) treated with rhGH (0.05 mg/kg/day). Anthropometric data
and fasting blood levels [e. g., Ir, insulin, glucose, glycated hemoglobin (HbA1c),
IGF-1, IGFBP-3, cholesterol, insulin resistance (HOMA-IR), and β-cell function (HOMA-β)]
were analyzed prior to and following rhGH therapy [mean (SD) follow-up of 1.47 (0.89)
years]. Insulin sensitivity (Matsuda index) was calculated before and after the glucose
load. Following rhGH therapy, an increase in IGF-1 [mean (SD) of 119.40 (62.47) ng/ml
to 439.08 (209.91) ng/ml, p=0.000], Ir [2.10 (1.03) μg/ml to 2.48 (0.78) μg/ml, p=0.036],
HOMA-IR [median (IQR) of 0.64 (0.45–1.30) to 0.92 (0.67–2.36), p=0.0206], and HOMA-β
values [45.00 (27.69–72.00) to 81.53 (51.43–132.00), p=0.0447] were observed. Multiple
regression analysis yielded no associations between Ir and metabolic and hormonal
parameters before rhGH treatment; however, on rhGH, the model (R2=0.56, adjusted R2=0.45) showed positive associations between Ir and IGF-1 standard deviation score and
HbA1c, and negative associations between Ir and fasting blood glucose, HDL-cholesterol,
and triglycerides. Despite manifestation of insulin resistance, rhGH application had
a positive effect on Ir regulation, and restored physiological conditions of lipid
and glucose metabolism.
Key words
irisin - growth hormone - insulin resistance - metabolic syndrome - HOMA-IR - beta-cell
function
