Biomedical Research 11 (1) 55-59, 1990

INTERRELATIONSHIPS BETWEEN THE THYROID GLAND AND GASTRIN SECRETION: EFFECTS OE TRIIODOTHYRONINE AND THYROIDECTOMY

MASAKI FUJIMURA 1 , GEORGE H. GREELEY2 , FELIX LLUIS3 and JAMES C. THOMPSON4 ‘Second Department of Surgery, Shiga University of Medical Science, Seta, Otsu, Shiga 520—~2l, Japan, 2Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77550, U.S.A. and Guest Professor of University of Shizuoka, Yada, Shizuoka 422, Japan, 3Department of Surgery, Hospital Sta. Creu; Sant Pau, Universidad Autonoma de Barcelona, Balcelona, Spain, and “Department of Surgery, The University of Texas Medical Branch, Galveston, Texas 77550, U.S.A.

ABSTRACT The effects of alterations in thyroid hormone status on secretion of gastrin in the adult rat and dog were studied to better understand previously reported changes in gastric secretion following hypophysectomy. Administration of triiodothyronine (T3) increased serum levels of gastrin in fed rats and both basal and fed gastrin levels in dogs. In T3-treated rats, antral gastrin and somatostatin levels were reduced sig- nificantly (P<0.05), whereas gastrin-releasing peptide (GRP) levels were increased. These data suggest that T3-treatment increases gastrin release by reducing antral concentrations of somatostatin and increasing antral concentrations of gastrin- releasing peptide, two peptides that are thought to participate in the regulation of gastrin secretion. Thyroidectomy significantly (P<0.05) decreased the serum gas- trin response to food ingestion but did not affect basal levels ofgastrin in fasted rats. Thyroidectomy also significantly decreased serum levels of gastrin stimulated by gastrin-releasing peptide in fed rats

A marked increase in the number of hypophy- served in humans. It is not clear whether the sectomies has been reported in humans (13). pituitary or thyroid gland participates in this In a number of species, hypophysectomy is phenomenon observed in humans. The objec- followed by a reduction in stomach weight, tive of these studies therefore, was to examine gastric acid secretion, and parietal cell count and the effect of alterations in the thyroid status size (13). The absence of pituitary gland hor- on secretion of gastrin in the rat and dog. Fur- mones can alter function of the stomach directly thermore, changes in antral concentrations of or indirectly. In fact, evidence for a direct action somatostatin and gastrin-releasing peptide, is given by the observation that replacement which are thought to regulate gastrin release, of growth hormone in hypophysectomized were measured, to clarify their possible role rats reverses a hypophysectomy-induced on gastrin secretion. decrease in antral gastrin stores in rats (3). It is well known that hypophysectomy MATERIALS AND METHODS results in hypothyroidism due to a depletion of thyroid stimulating hormone. Hypogas- Animals trinemia during hypothyroidism (14) is ob- Male Sprague-Dawley rats (220—225 g) were