Differential expression of alpha- and beta-thyroid hormone receptor genes in the developing rat brain under...

One of the most alarming observations of iodine deficiency disorders (IDD) is neurological cretinism which is caused due to lack of T3 during the crucial stages of brain development. We have developed an iodine-deficient rat model to study the pattern of T3 receptor genes expression in the brain during postnatal development under iodine deficiency. We observed increased expression of c-erbA-alpha 2 and -beta 1 T3 receptor transcripts while c-erbA-alpha 1 remains unchanged in the brain of the iodine-deficient neonates compared with their euthyroid counterparts. Up-regulation of the beta 1 form in the developing brain under iodine deficiency is suggestive of an adaptive process coming into play to protect it from the damages that are inflicted due to hypothyroidism. Though the significance of the increased alpha 2 form in the iodine-deficient rat brain has not yet been ascertained, it can be conjectured that it acts as a homeostatic control over 'functional receptor' (namely beta 1) under developmental hypothyroidism.