Insulin release in response to calcium in the diagnosis of insulinoma.

A calcium infusion (4 mg Ca++/kg/hr) significantly increased plasma insulin levels and reduced blood glucose in 4 patients with insulin-secreting pancreatic islet cell tumors. These parameters were not altered by a similar infusion of calcium in normal volunteers, 2 patients with alimentary hypoglycemia, and 2 with functional hypoglycemia. No difference in response was observed between patients with benign and malignant beta-cell tumors. Infusion of diazoxide (600 mg) with calcium blocked the stimulation of the latter on insulin secretion. The results indicate the usefulness of calcium infusion in the diagnosis of insulin-secreting tumor.

Thyrotropin-releasing hormone (TRH)-induced growth hormone (hGH) responses in cirrhotic men.

The plasma growth hormone (hGH) responses to an intravenous challenge of 400 micrograms of thyrotropin-releasing hormone (TRH) were evaluated in 14 normal controls and in 29 chronic alcoholic men. The normal controls had either a minimal or no hGH response to TRH, having basal hGH levels of 0.9 +/- 0.2 ng per ml and peak hGH levels of 2.0 +/- 0.5 ng per ml. In contrast, the chronic alcoholic men had a basal hGH level of 2.8 +/- 0.4 ng per ml, 3 times the basal level of the normal controls (P less than 0.01). The peak hGH response of the alcoholic men was 7.4 +/- 1.5 ng per ml (P less than 0.01). The 29 alcoholic men could be divided into two groups based upon the presence or absence of cirrhosis as determined by liver biopsy. The 16 alcoholic men with cirrhosis had greater basal hGH levels (3.5 +/- 0.6 ng per ml) and peak hGH levels (9.5 +/- 2.3 ng per ml) than did the 13 alcoholic men without cirrhosis (basal hGH 2.1 +/- 0.6 ng per ml, peak hGH 4.9 +/- 1.5 ng/ml). Plasma estradiol levels were similar in the normal controls and in the alcoholic men. In contrast, plasma estrone was greater in the alcoholic men (32.2 +/- 3.5 pg per ml) than in the normal controls (18.9 +/- 1.8 pg per ml) (P less than 0.05). However, when the plasma estrone levels of alcoholic men with cirrhosis were compared to those of the alcoholic men without cirrhosis no difference existed. Thus it is difficult to ascribe the increased hGH responses of the cirrhotic alcoholic men when compared to those of the noncirrhotic alcoholic men as being a result of increased basal estrogen levels.

Simultaneous ectopic production of parathyroid hormone and calcitonin.

Two patients with cancer were evaluated in whom there was evidence for the simultaneous ectopic production of parathyroid hormone (PTH) and calcitonin (CT). One patient had a gastric carcinoid and the other had a pancreatic islet cell carcinoma. Abnormal concentrations of parathyroid hormone and calcitonin were demonstrated by radioimmunoassay in the peripheral blood of each patient and in the gastric tumor. In the pancreatic tumor, immunohistologic studies also demonstrated the presence of CT and PTH and suggested that each hormone was produced by different cells of the tumor. Plasma concentrations of the hormones responded to functional tests of secretion and to tumor chemotherapy. These studies demonstrate the simultaneous ectopic production of the two physiologically antagonistic hormones, PTH and CT, and confirm their value as diagnostic markers for several types of malignancies.

Triiodothyronine and thyroxine in hyperthyroidism. Comparison of the acute changes during therapy with antithyroid agents.

In 66 untreated patients with hyperthyroidism, serum triiodothyronine (T(3)) and thyroxine (T(4)) concentrations were measured by immunoassay. The mean T(3) level was 478+/-28 ng/100 ml (all values mean+/-SEM) and the T(4) was 20.6+/-0.6 mug/100 ml. The serum T(4)/T(3) ratio by weight was 48+/-2 as opposed to a value of 71+/-3 in euthyroid adults. There was a significant inverse correlation of the T(4)/T(3) ratios with serum T(3) (r=0.77; P<0.01) but not with serum T(4)(r=0.21). These results suggested that relative overproduction of T(3) is consistently present in patients with hyperthyroidism. To examine the acute effects of various antithyroid agents on serum T(3) and T(4) concentrations, iodide, propylthiouracil (PTU), and methylmercaptoimidazole (MMI) were given alone to mine patients, and serial T(3) and T(4) measurements were made. There was an acute decrease in serum T(3) over the first 5 days in the three iodide and three PTU-treated patients which was greater than that seen in the MMI group. This suggested that PTU and MMI had different effects on T(3) production. To compare the effects of PTU and MMI under conditions in which thyroidal hormone release was minimized, these drugs were given in combination with iodide. The mean daily dosage of PTU was 827 (n=11) and of MMI was 88 (n=8). In the PTU+iodide group, the initial serum T(3) concentration was 586+/-61 ng/100 ml and decreased significantly to 326+/-41 on day 1 and to 248+/-21 on days 2 and 3, respectively, and did not change further on days 4 and 5. In the MMI + iodide group, basal serum T(3) was 645+/-90 ng/100 ml and decreased to 568+/-81, 452+/-73, and 344+/-51 on days 1, 2, and 3, respectively, and did not change thereafter. While the initial T(3) concentrations in serum were not different in the PTU and MMI groups, the T(3) concentrations in the PTU patients were significantly lower on days 1 and 2 and during the apparent plateau period on days 3-5. Serum T(4) concentrations decreased gradually in both groups, from 23.9+/-2.0 mug/100 ml, initially, to 17.5+/-1.6 on day 5 in the PTU group and from 22.0+/-2.6 to 14.6+/-2.0 in the MMI-treated patients. The T(4) values were not significantly different at any time. These changes resulted in increases in the serum T(4)/T(3) ratios in both groups, but these ratios were substantially higher in the patients treated with PTU + iodide. The initial serum T(4)/T(3) ratio was 43+/-3 and increased to 74+/-7 and 88+/-7 on days 1 and 2 in the PTU group, reaching a plateau value of 91+/-7 during days 3-5. Comparable values for MMI-treated patients were 35+/-2, 42+/-3, 52+/-6, and 54+/-3 during the plateau period. Previous investigations have shown that PTU inhibits T(4) deiodination in hyperthyroid patients and decreases T(3) production from T(4) in animals. The greater acute decrease in serum T(3) and the higher serum T(4)/T(3) ratios in the PTU-treated patients seems best explained by an inhibition of peripheral T(3) production by this agent. This conclusion is further supported by a direct relationship between the T(4)/T(3) ratio on days 3-5 and the dose of PTU administered. These results further suggest that both thyroidal and extrathyroidal pathways contribute substantially to the apparent overproduction of T(3) in hyperthyroidism.

Serum triiodothyronine and thyroxine in the neonate and the acute increases in these hormones following delivery.

Low triiodothyronine (T(3)) and high normal thyroxine (T(4)) concentrations are present in cord sera from full term infants. To examine this phenomenon further, radioimmunoassay of T(3) and T(4) was carried out in paired maternal and cord sera as well as capillary sera from neonates at different intervals after delivery. Free T(3) and free T(4) concentrations were also estiamted in cord and maternal sera by equilibrium dialysis. In 12 paired specimens, the T(3) concentration in cord sera was significantly lower than the maternal level (51+/-4 vs. 161+/-11 ng/100 ml, mean +/-SE). Mean free T(3) concentration was also lower in the cord samples (0.15+/-0.02 vs. 0.31+/-0.04 ng/100 ml). whereas total and free T(4) concentrations were not significantly different. Umbilical vein and artery samples from 11 neonates did not differ significantly in their T(3) and T(4) concentrations. In seven infants the mean T(3) concentration increased from 51+/-3 ng/100 ml at delivery to 79+/-13 at 15 min and 191+/-16 at 90 min. In four other infants the mean T(3) concentration at 24 and 48 h was not significantly different from the 90 min value of the previous group. Less pronounced changes were observed for T(4) which increased from 12.3+/-2.0 mug/100 ml (mean +/-SE) at delivery to 14.1+/-1.9 at 90 min and appeared to have reached a plateau at approximately twice the cord value by 24-48 h after delivery.The maternal-fetal gradient observed for free T(3) is further evidence of the autonomy of the fetal thyroidpituitary axis. The time course of the abrupt increase in serum T(3) in the neonate suggests that it results from the earlier acute increase in serum TSH which occurs shortly after birth. This suggests that the neonatal thyroid contains significant quantities of T(3). Therefore, unavailability of thyroidal T(3) does not appear to explain the low total and free T(3) concentrations present in the sera of newborns.