Thyrostimulin (a TSH-like Hormone) Expression in Orbital and Thyroid Tissue

Objective: To investigate gene expression of thyrostimulin in orbital and thyroid tissue from patients with and without Graves' disease. Design: Real-time reverse transcriptase polymerase chain reaction (RT-PCR) was used for detection of thyrostimulin gene expression in intraorbital adipose tissue from patients with severe ophthalmopathy and thyroid healthy controls in addition to thyrostimulin expression in normal thyroid tissue, multinodular goiter tissue, and Graves' thyroid tissue. Main Outcome: In intraorbital tissue, thyrostimulin expression was identified in both patients and controls with fluorescence intensities varying between 0.23 and 0.88 in patients and 0.29 and 8.9 in controls before treatment with DNase. The signal of thyrostimulin was weak or absent in intraorbital adipose tissue from patients with ophthalmopathy and thyroid healthy controls after treatment of samples with DNase. This was in contrast to the expression of the thyroid-stimulating hormone (TSH) receptor and the housekeeping gene cyclophilin A that were detected both before and after DNase treatment. Similar results were found when analyzing human and rat thyroid tissue. Conclusions: Neither did we demonstrate gene expression of thyrostimulin in intraorbital adipose tissue or in thyroid tissue, nor could we confirm earlier findings in rat thyroid tissue. Whether thyrostimulin is a regulator of thyroid function has to be further investigated in future studies.