IGF1 deficiency in newly diagnosed Graves' disease patients

Thyroid hormones influence the GH/IGF1 axis, but previous studies have reported discrepant results regarding serum IGF1 levels in hyperthyroidism. We have therefore investigated, at diagnosis, the relationship between serum IGF1 levels and the main characteristics of Graves' disease (GD): severity of hyperthyroidism, goiter size, presence of active Graves' ophthalmopathy (GO), antythyroid antibodies status and titer.

This cross-sectional study included 98 newly diagnosed hyperthyroid patients with GD who presented consecutively at our clinic. The main measured parameters were: TSH, FT4, FT3, TT3, thyroglobulin,anti-thyroid peroxidase antibodies (TPOAb), anti-thyroglobulin antibodies (ATA), thyrotropin receptor antibodies (TRAb), IGF1. Patients were considered IGF deficient if IGF1 z score was ≤-2SD from mean for age.

In GD patients, men had higher IGF1 levels (p=0.023) and IGF1 z scores (p=0.013) than women. 18.4% of GD patients were, at diagnosis, IGF1 deficient. Compared to patients without IGF1 deficiency, these patients presented higher thyroglobulin (median=72.55, IQR=116.02 vs median=11.40, IQR=80.74 ng/ml, p=0.002) and FT3 (median=11.30, IQR=7.64 vs median=7.33, IQR=5.72 pg/ml, p=0.027), and lower ATA (median=20, IQR=0 vs median=34.05, IQR=161 iu/ml, p<0.001) levels. Thyroglobulin was independently associated with IGF1 deficiency (AUROC=0.732, 95% CI: 0.620-0.844, p=0.002; cut-off for thyroglobulin=50.40 ng/ml, Se=77.8%, Sp=70%). IGF1 status was not influenced by gender (p=0.084), current smoking (p=0.558), goiter size (p=0.533), active ophthalmopathy (p=0.334), TRAb (p=0.239) or TPOAb status (p=0.367).

Nearly one fifth of newly diagnosed GD patients had IGF1 deficiency. IGF1 deficiency was associated with lower ATA titers, higher thyroglobulin levels and more severe FT3 hyperthyroidism at diagnosis.