Abstract

Background:The relationship of altered thyroid status with GH and components of insulin-like Growth factor (IGF-1) axis is complex and not fully understood. We aimed to evaluate changes in Acid labile subunit (ALS) and IGF-1 in hyperthyroidism, before and after normalization of thyroid status.

Methods:Thirty-four hyperthyroid patients matched with 36 normal controls were studied. The patients and controls were assessed at baseline and the patients were followed up prospectively and re-assessed after 6 months of treatment with antithyroid drug (ATD) (carbimazole). On each occasion, blood was collected for measurement of ALS, IGF-1, glucose, insulin, intact proinsulin and thyroid function.

Results: Pre-treatment levels of ALS (p=0.012) and IGF-1 (p=0.007) were significantly lower in patients than controls. Five to 10 weeks post-treatment with ATD, all patients were restored to euthyroidism. ALS and IGF-1 levels increased significantly to similar levels of controls after 6 months of ATD. Within the patients, ALS (p=0.049) and IGF-1 (p=0.001) correlated inversely with free T3, whereas, only IGF-1 (p=0.005) correlated inversely with free T4.

Conclusion:These results demonstrate that untreated hyperthyroidism is associated with reduction in ALS and IGF-1. Due to the fact that ALS and IGF-1 were related inversely with thyroid status and their concentrations were normalized with euthyroidism, it would be possible to consider their reductions as helpful markers of altered thyroid status, namely hyperthyroidism.

Keywords

ALS, IGF-1, hyperthyroidism, medical treatment, insulin-like growth factor, IR, radioactive iodine uptake, HOMA, coefficients of variation, CV, IGF-binding protein, GH, growth hormone