A case of hyperthyroidism caused by the syndrome of inappropriate secretion of thyroid stimulating hormone. Association of primary hypergonadotropic hypogonadism.

Abstract

A 49-year-old man with hyperthyroidism caused by the syndrome of inappropriate secretion of TSH (SITSH) is reported. A diagnosis of infertility and hypospermatogenesis due to primary hypergonadotropic hypogonadism had been made 10 years ago. Serum TSH levels were inappropriately elevated with thyrotoxic high levels of thyroid hormone in serum, but no tumorous mass was demonstrated in the pituitary gland. The non-tumorous pituitary resistance of TSH to thyroid hormonal suppression was confirmed by low levels of glycoprotein a-subunit and low a-subunit/TSH ratios in serum before and after the stimulation by TRH. In addition, the patient had elevated levels of LH and FSH in serum, and their exaggerated responses to LH-RH, although serum testosterone concentrations were normal, indicating primary hypogonadism. It is of interest that SITSH appeared in the hypogonadal patient who was preceded by the long standing hypersecretion of LH and FSH.