A third mechanism is central nervous system/psychological: autoimmunity, which may affect brain excitability or autonomic regulation, leading to decreased libido independent of thyroid hormone levels; indeed, altered central excitability was observed in HT independent of TSH, and depressive symptoms (more frequent in HT) correlate with worse sexual function (especially lubrication and satisfaction domains) in euthyroid patients [13]. The gene discussed is TG; the disease is Autoimmunity.