Expression of thyroid-stimulating hormone receptors and thyroglobulin in limbic regions in the adult human brain

Expression of the human thyroid-specific proteins, thyroid-stimulating hormone receptor (TSH-R) and thyroglobulin (TG) in non-thyroid tissue is well-documented. TSH-R has been identified in the heart, kidney, bone, pituitary, adipose tissue, skin and astrocyte cultures. TG has been identified in the skin, thymus and kidney. However, none of those previous studies had identified TSH-R or TG in specific human brain regions. Previously, a pilot study conducted by our group on normal adult human brain demonstrated TSH-R and TG in cortical neurons and cerebral vasculature, respectively, within various brain areas. In the present study, we extend this investigation of thyroid proteins specifically in limbic regions of normal human brain. Forensic human samples of amygdalae, cingulate gyrii, frontal cortices, hippocampii, hypothalamii, and thalamii were obtained from five individuals who had died of causes unrelated to head injury and had no evidence of brain disease or psychological abnormality. Tissues were probed with commercial polyclonal antibodies against human TSH-R and TG which resulted in the significant demonstration of neuronal TSH-R in all limbic regions examined. Other novel results demonstrated TG in vascular smooth muscle of all limbic regions and in some neurons. Finding thyroid proteins in limbic areas of the human brain is unique, and this study demonstrates that cerebro-limbic localisation of thyroid proteins may have potential roles in neuro-psycho-pharmacology.