triiodothyronine--reverse and Hypoglycemia

Previously, it has been observed that dexamethasone or adrenaline-induced hyperlipaemia in blood of chicken was significantly reduced after administration of reverse triiodothyronine (rT3). The present experiment was performed on chicken to determine the altered circulating non-esterified fatty acids (NEFA) induced by physiologically enhanced endogenous corticosterone and catecholamines may also be influenced by rT3. Rise of both hormones were induced by insulin administration. Changes in circulating glucose, corticosterone and catecholamines were additionally measured. Following insulin injection blood glucose fell on the average by 32.7% below control at 2 h of the experiment. Additional treatment with rT3 (rT3 + insulin group) gradually attenuated this decrease and at 4 and 6 h of the experiment it was 17.1% and 12.9% below control, respectively, suggesting on slight inhibition by rT3 of insulin-stimulated glucose utilization. Exposure to insulin significantly increased NEFA levels to about 670% above control group. Additional treatment with rT3 reduced this increase to 309% of control, suggesting inhibition of lipolysis by rT3. Similar alterations were observed in plasma corticosterone levels. Insulin treatment peaked the corticosterone levels maximally by 507.6% above control. Additional treatment with rT3 abolished this rise in the averages to 194.2% above control, possibly by interaction of rT3 with hypothalamo-adrenal axis. Insulin injection increased plasma catecholamines on the average by 21.5% and 53.4% for adrenaline and noradrenaline respectively. Supplementary treatment with rT3 intensified this rise by 55.6% and 71.6% respectively. The obtained results suggest on inhibitory effect of rT3 on hypoglycaemia, hyperlipaemia and plasma corticosterone concentrations in chickens treated with insulin. Contrary to this, rT3 enhanced the rise of plasma catecholamines due to insulin treatment. The obtained data favour the assumption that hypometabolic properties of rT3 depends mainly upon reduced supply of NEFA as a result of restricted lipolysis and to a lesser extent upon the supply of glucose.

Topics: Animals; Blood Glucose; Chickens; Corticosterone; Fatty Acids, Nonesterified; Hypoglycemia; Hypoglycemic Agents; Insulin; Triiodothyronine, Reverse

Biliary excretion of reverse triiodothyronine (rT3) was estimated in rats during hypoglycemia induced by a 10-min infusion of 1 U of insulin (INS) and for the following 5 h. During that period an increase in biliary rT3 was found. This was seen also during the infusion of exogenous glucagon (10 micrograms in 1.2 ml of saline per 1 h for 5 h) given independently of INS. The infusion of glucose (1 g/kg per 50 min or 2 g/kg per 110 min) following INS infusion delayed the increase in rT3. The increase in rT3 was prevented by actinomycin D (1 mg/kg) when injected before (90 min), but not after (30 min) INS, and also by cycloheximide (2.5 mg/kg) injected immediately before INS. The same dose of cycloheximide also prevented a similar increase of rT3 during the infusion of exogenous glucagon. Verapamil (5 mg/kg divided into five doses per 4 h) blunted the increase of rT3. These data indicate that following INS injection counter-regulatory hormones may be responsible for the increased production of rT3; this altered metabolic activity apparently is dependent on protein synthesis.

Topics: Animals; Bile; Cycloheximide; Dactinomycin; Glucose; Hypoglycemia; Insulin; Male; Rats; Rats, Wistar; Triiodothyronine, Reverse; Verapamil

Ethanol-induced hypoglycemia after 44 hours of complete fasting was allowed to last for four hours. S-T3 decreased significantly (p less than 0.05), by 16.5%, S-rT3 remained unchanged and S-cortisol increased significantly (p less than 0.01). No correlation was found between S-T3 and S-cortisol. An association was found between S-T3 and blood glucose (p less than 0.05). An acute low S-T3 was achieved by depressing the peripheral availability and utilization of glucose. No association to a simultaneous increase in S-cortisol was found. An increase in S-rT3 failed to appear, probably also due to glucopenia.

Topics: Adult; Blood Glucose; Ethanol; Female; Humans; Hydrocortisone; Hypoglycemia; Insulin; Male; Middle Aged; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse

Topics: Asphyxia Neonatorum; Humans; Hypoglycemia; Infant, Newborn; Infant, Newborn, Diseases; Infections; Meconium; Pneumonia, Aspiration; Surgical Procedures, Operative; Thyroid Gland; Thyroid Hormones; Thyrotropin; Thyroxine; Thyroxine-Binding Proteins; Triiodothyronine; Triiodothyronine, Reverse

The effect of insulin-induced hypoglycemia on serum thyroid hormone concentrations was studied in nine healthy individuals. Before, during and after the hypoglycemia blood samples were taken for measurement of the concentrations of glucose, thyroxine (T(4)), triiodothyronine (T(3)), reverse triiodothyronine (rT(3)), catecholamines and pituitary hormones.There was no change in the mean serum T(4) level (+/- the standard error of the mean) of 67 +/- 2 mug/l. However, the T(3) concentrations rose from a mean basal level of 1.86 +/- 0.06 mug/l to a mean peak of 2.51 +/- 0.21 mug/l (P < 0.01) at 45 minutes after the insulin injection, and the rT(3) concentrations fell from a mean basal level of 0.184 +/- 0.008 mug/l to a mean nadir of 0.171 +/- 0.022 mug/l (not a significant change). The mean peak epinephrine level was 545 +/- 103 ng/l and it occurred between 30 and 45 minutes after the insulin injection; the mean peak norepinephrine level was 584 +/- 114 ng/l and it occurred between 30 and 90 minutes after the injection. The growth hormone levels reached a mean peak of 26.1 +/- 4.8 mug/l and the plasma cortisol levels rose to 215 +/- 9 mug/l. The mean basal prolactin level was 8.5 +/- 0.9 mug/l; in five subjects there was a rise to a mean peak of 50.6 +/- 14.6 mug/l, whereas in the remaining four no significant increase occurred. No correlation was found between the changes in the serum T(3) concentration and any of the other factors studied.It was concluded that acute hypoglycemia is associated with a rapid increase in the serum T(3) concentration.

Topics: Adult; Blood Glucose; Epinephrine; Female; Growth Hormone; Humans; Hydrocortisone; Hypoglycemia; Insulin; Male; Norepinephrine; Thyroxine; Triiodothyronine; Triiodothyronine, Reverse