Effect of Acute Hyperglycemia - and Isoproterenol - induced Hypothalamic Somatostatin Release on the Thyroid Hormone Releasing Hormone - induced Thyroid Stimulating Hormone Secretion / 대한내분비학회지

ABSTRACT

BACKGROUND: Acute hyperglycemia stimulates somatostatin (SRIH) release from the hypothalamus, and which in turn suppress growth hormone (GH) secretion and thyroid stimulating hormone (TSH) from the anterior pituitary gland. Beta-adrenergic pathway is known to stimulate the hypothalamus SRIH release. Recently, We demonstrated that isoproterenol, a beta-adrenergic agonist, had an additional suppressive effect on the suppression by glucose of GHRH-stimulated GH response. Therefore, the present study aimed to determine whether isoproterenol has an additional suppressive effect on the suppression by glucose of TRH-stimulated TSH response. METHODS: Seven healthy young men, aged 24 to 27 years, were studied. Four different TRH stimulation tests were carried out. (Test 1) TRH (Hoechst AG, Germany), 200 microgram bolus, was given intravenously at 0 minute. (Test 2) Glucose, 100 g, was given orally 30 min before TRH administration. (Test 3) Isoproterenol(Isuprel, Sanofi Winthrop, USA), 0.012 pg/kg, was infused continuously for 120 min after TRH administration. (Test 4) After pretreatment with glucose as Test 2, isoproterenol and TRH were administered as Test 3. RESULTS: Oral glucose ingestion significantly suppressed the TRH-stimulated TSH secretion. Isoproterenol infusion significantly suppressed the TRH-stimulated TSH secretion. Glucose-induced suppression of the TSH response was significantly greater than that by isoproterenol. 1soproterenol infusion after glucose pretreatment did not show any additional suppressive effect on the glucose-induced suppression of TSH response to TRH. CONCLUSION: The results suggest that isoproterenol infusion in addition to glucose pretreatment before the TRH stimulation test is not necessary for the development of stronger stimulation test for the hypothalamic somatostatin secretion.