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.