PROLACTIN ACTIVITY IN JUVENILE HYPOTHYROIDISM AND PRECOCIOUS PUBERTY

Abstract

Two 8-year-old girls, one of whom had Down's syndrome, presented with myxedema and precocious sexual development. Elevated circulating thyrotrophin (TSH), luteinizing hormone (LH), follicle-stimulating hormone (FSH) levels, and prolactin activities were documented. Following treatment with thyroid extract, the abnormal clinical findings and the elevated levels of pituitary hormones returned to normal. The results of studies in our patients suggest a derangement in hypothalamic pituitary regulatory mechanisms. It is postulated that low circulating thyroxine may increase the hypothalamic content of thyroid-releasing hormone (TRH) and the sensitivity of the pituitary to TRH stimulation resulting in increased release of TSH and prolactin. The elevated plasma gonadotrophins may result from a nonspecific stimulation of the hypothalamic gonadotrophin-releasing hormone (LH-FSH-RH) or from a direct stimulation by prolactin of the LH-FSH-RH.