The Relevance of the TRH-Test in the Differential Diagnosis of Exophthalmos

The recent discovery of the hypothalamic releasing hormones has greatly advanced our knowledge of the hypothalamic-pituitary system. Each anterior pituitary hormone has its hypothalamic counterpart in a release stimulating and/or inhibiting hormone. Available for clinical use are the hypothalamic hormones TRH (thyrotrophin releasing hormone) and LHRH (luteinizing hormone releasing hormone, which also stimulates the release of the follicle stimulating hormone FSH). The pituitary thyrotrophin and gonadotropin reserve can now be asssessed accurately by injecting TRH and LHRH, and measuring the thyrotrophin and gonadotropin response respectively. The main clinical use of the TRH-stimulation test is however in the diagnosis of thyroid disorders.