Serum gastrin levels in patients with thyroid dysfunction.

Fasting serum gastrin levels measured by radioimmunoassay were found to be elevated in patients with hyperthyroidism and low in patients with hypothyroidism. The oral administration of beef extracts resulted in more increase of serum gastrin in hyperthyroid patients than in normal subjects. After restoration of the euthyroid state by treatment, no more increase in serum gastrin levels was observed. Slight correlation between gastrin levels and serum T3 levels was observed in pretreated hyperthyroid patients (r = 0.40), but significant correlation between them was found after restoration of the euthyroid state by treatment (r = 0.50). However, it seemed to be able to divide into two groups in the pretreated patients. One was a patient group whose gastrin levels correlated closely to serum T3 levels (r = 0.83, p less than 0.01). The other was a group whose serum gastrin levels remained in low even in high T3 levels (r = 0.81, p less than 0.01). Different sensitivity to thyroid hormone in the G-cells of gastrointestinal tract may exist in these two groups, because patients age and duration of their illness were not different between them.