PIT1 abnormality.

The PIT1 gene product, Pit-1/GHF-1, binds to and transactivates the promoter sequences of the growth hormone, prolactin, and thyroid-stimulating hormone beta (also called thyrotropin) subunit genes. Abnormalities of the PIT1 gene, which encodes a pituitary-specific POU-domain DNA binding factor, cause a combined deficiency of growth hormone, prolactin, and thyrotropin (PIT1 abnormality). PIT1 abnormality is a typical 'transcription factor disease (abnormality)', as DNA-binding studies and transactivation studies with mutant Pit-1/GHF-1 protein and its target sequences made clear how the mutated protein causes the abnormality. PIT1 abnormality occurs both recessively and dominantly, according to the function of the mutated protein. Furthermore, observation of patients of different ages with the same mutation showed progressive phenotype as the patients grow old.