Thyroid hormone regulation of human pituitary alpha subunit gene expression.

The thyroid hormone T3 exerts an inhibitory effect upon pre-translational expression of the alpha subunit gene in the anterior pituitary. In the intact animal oestrogen alone is without effect upon alpha gene expression but oestrogen modulates the influence of T3 deficiency upon the alpha gene. T3 effects upon alpha transcription are mediated via sequences within 98 bp of the transcriptional start site of the gene and similar 5' flanking sequences of the alpha gene mediate both T3 regulation and oestrogen modulation of T3 inhibition. This oestrogen effect may be mediated directly via interaction of the oestrogen receptor with the alpha gene thyroid hormone response element to which the oestrogen receptor is able to bind.