Biomedical subjects

C H Bivens

Publications and source records attributed to C H Bivens.

12 recordsLinked to original sources

PubMed1976

Inhibitory effect of serotonin antagonists on growth hormone release in acromegalic patients.

We evaluated the effect of the serotonin antagonists cyproheptadine (Cypro) and methysergide (Methy) on growth hormone secretion in six patients with acromegaly. Two days administration of Cypro decreased the plasma GH concentration during oral glucose tolerance tests in four of the six patients evaluated; 2 days administration of Methy reduced the plasma GH levels of only one of the four patients evaluated. The one patient whose plasma GH concentration was lowered by Methy, did not have a decrease in plasma GH concentration after Cypro administration. Acromegalic patients have normal serum serotonin concentration and normal 5-hydroxyindoleacetic acid excretion. If Cypro lowers plasma GH by antagonizing serotonin, our data would suggest that serotoninergic neuronal pathways are important in the regulation of pituitary GH secretion in some patients with acromegaly.

Acromegaly↗

PubMed1975

The role of cortisol and growth hormone in the counter-regulation of insulin-induced hypoglycemia.

Four normal volunteers underwent a control insulin tolerance test (ITT) and an insulin tolerance test (ITT) after two days administration of the serotonin antagonist cyproheptadine (Cypro). Cypro administration resulted in an 81 +/- 11.4% (M +/- SEM) reduction in cortisol secretion and a 73 +/- 15.1% reduction in growth hormone (GH) secretion. Despite the reduction in hypoglycemia-induced cortisol and GH secretion, there was a similar decline and recovery of plasma glucose in the control ITT and the ITT after Cypro administration. Although previous studies indicate that normal basal levels of cortisol and growth hormone are needed for normal counter-regulation after insulin-induced hypoglycemia, augmented secretion of these hormones is probably not essential for this response. Hypoglycemia-induced increases in epinephrine and glucagon, secretion may contribute to the restoration of the normal plasma glucose concentration after insulin-induced hypoglycemia.

Blood Glucose↗

PubMed1975

Effect of cyproheptadine administration on insulin secretion in acromegalic, diabetic and normal subjects.

The effect of cyproheptadine (Cypro) and Placebo administration on insulin secretion and glucose utilization following i.v. glucose (IVGTT) was evaluated in 8 normal, 7 diabetic and 8 acromegalic subjects. Five of the diabetic subjects had overt diabetes and two of the diabetic subjects had "chemical" diabetes (oral GTT). One of the acromegalic subjects had overt diabetes, while one had borderline glucose tolerance and six had normal glucose tolerance (oral GTT). Cypro increased insulin secretion in the acromegalic but not in the diabetic or normal subjects. Methysergide (Methyl) increased insulin secretion in acromegalic and diabetic subjects but not in normal subjects. Methy and Cypro both increased insulin secretion in the same acromegalic subjects. None of the three groups of subjects had a modification in insulin secretion following Placebo administration. Neither Placebo, Cypro or Methy altered the glucose utilization rate contant (KG). There was no change in insulin half life or tissue sensitivity to insulin from Cypro (normal and acromegalic subjects) or Methy (normal subjects) administration. Despite their increase in insulin secretion in response to serotonin antagonists, acromegalic subjects have normal urinary 5-hydroxyindoleacetic acid excretion and normal serum serotonin concentrations. Their response cannot therefore be attributed to a generalized overproduction of serotonin.

Acromegaly↗

PubMed1975

Glucose intolerance in the carcinoid syndrome.

We assayed glucose tolerance and insulin secretion in ten patients with metastatic carcinoid tumors and the carcinoid syndrome ("active tumors") and in seven patients with metastatic carcinoid tumors without the carcinoid syndrome ("inactive tumors"). The patients with "active tumors" had elevated serum serotonin levels while the patients with "inactive tumors" had normal serum serotonin levels. Of the ten patients with "active tumors," five had diabetic and three had borderline intravenous glucose disposal rate constants (KG = 0.88 +/- 0.07, M. +/- S.E.M.). Their KG was significantly lower (p less than 0.01) than a group of age-matched normals. All of the patients with "inactive tumors" had normal KG values (KG = 1.67 +/- 0.24). Their KG did not differ from that of age-matched normal subjects. Both groups of carcinoid patients had a comparable decrease in their insulinogenic index. Two days' administration of the serotonin antagonist cyproheptadine (Cypro) to eight of the patients with "active tumors" resulted in a significant increase in the "insulinogenic index" (50%) but a nonsignificant increase in the KG (12%). Administration of p-chlorophenylalanine, a compound that blocks serotonin synthesis, resulted in an increase in both the KG (60%) and the "insulinogenic index" (55%). The insulin half-life (t1/2) of patients with "active tumors" (6.1 +/- 0.4 min.) did not differ from the t1/2 of normal subjects (6.6 +/- 0.4 min.), suggesting that the decreased plasma insulin levels following intravenous glucose were due to impaired insulin secretion rather than accelerated insulin destruction. Seven of the patients received treatment with the antitumor agent streptozotocin (Strepto). The patients received cumulative doses of from 70 to 300 mg. of Strepto per kilogram body weight with no impairment in glucose tolerance or insulin secretion. We conclude that there is high incidence of glucose intolerance (80%) and impaired insulin secretion in patients with the carcinoid syndrome and that serotonin plays a role in producing these alterations.

Adult↗

PubMed1974