Administration Of Triiodothyronine Research Articles

Influence of Triiodothyronine on Feedlot Performance and Carcass Characteristics of Growing-Finishing Swine

Three experiments, involving a total of 147 pigs, were conducted to determine the effect of various levels and periods of administration of triiodothyronine on the weight gain, feed conversion, gland weights and carcass characteristics of growing-finishing swine. Weanling pigs were fed levels of 25, 50, 75, 125, 250 and 500 mg. triiodothyronine/ton of feed throughout the growing-finishing period. Pigs were also fed 50 mg. triiodothyronine commencing at 110 lb. and 150 lb. body weight. In one experiment a 14% protein ration was compared to a 21% protein ration. Results are as follows: Levels of 125 mg. and above appeared to be too high by virtue of a reduction in the efficiency of feed conversion. No consistent improvement in gains or feed conversion was elicited at levels of 25–75 mg., although in one instance a statistically significant improvement in gains (P<.05) was observed at a 50-mg. level of supplementation. Triiodothyronine supplementation tended to reduce the size of the thyroid gland, but appeared to have no affect on the size of the pituitary and adrenal glands. Carcass measurements revealed no significant effects due to triiodothyronine administration. Triiodothyronine effects were not significantly influenced by the protein levels studied. However, pigs fed 14% protein rations gained faster, converted feed more efficiently (P<.01), gave higher dressing percentages (P<.01) and were thicker in backfat (P<.01) than comparable pigs fed 21% protein rations.

Thyroid hormone administration and ovarian and adrenal activity in rats bearing hypothalamic lesions.

Bilaterally symmetrical electrolytic lesions which damaged arcuate nucleus and median eminence in the hypothalamus of adult female rats regularly produced atrophy of the reproductive tract (and reduced thyroid function) but were without consistent effect on adrenal morphology. Hypothalamic obesity and genital hypoplasia were frequently associated. Thyroxine and triiodothy-ronine administration to intact animals induced ovarian and uterine hypertrophy as well as adrenal enlargement. Similar treatment in operated rats failed to reverse the gonadal atrophy but did not interfere with the adrenal hypertrophy. A differential response was also found in rats made severely hypo-thyroid with propylthiouracil prior to hypothalamic destruction. Ovarian atrophy without concomitant change in adrenal cortex occurred following placing of lesions and goitrogen withdrawal. Evidences of adreno-cortical activation were seen in rats with diabetes insipidus (lesion-induced) and in chronically starved animals with marked hypoth...

Effect of tranquilizing agents on radioactive iodine uptake in the thyroid gland.

There are many patients who arouse clinical suspicion of having hyperthyroidism yet who do not suffer from true thyrotoxicosis. These patients usually have no enlargement of the thyroid gland and lack the true eye signs of toxic diffuse goiter (Grave's disease). They are nervous and insomnic, complain of palpitation of the heart, and have some degree of tachycardia. They may or may not show evidence of weight loss and may even be obese. A routine study of 24-hour uptake of radioactive iodine (I 131 ) by the thyroid gland in these persons will often show an uptake which is in the upper normal or even in the toxic range. 1 Further studies may reveal normal thyroid function by means of such tests as conversion ratios (ratio of inorganic to organic iodine in plasma) and plasma protein-bound iodine studies. It has been shown that oral administration of thyroid extract or triiodothyronine will

The effect of triiodothyronine administration on the elevated protein-bound iodine level in human pregnancy

1.1. Depression of the elevated PBI level of pregnant women followed the administration of triiodothyronine in the second and third trimesters.2.2. The data reveal that the pituitary-thyroid relation is normally responsive in pregnancy, and that the elevation in PBI is not due to the abnormal relation seen in hyperthyroidism.3.3. The data tend to exclude the possibility of more than limited placental secretion of thyrotropin.4.4. The implications are discussed of the finding that larger doses of triiodothyronine were required to suppress the PBI level in the last trimester of pregnancy than in the preceding trimester.

The metabolism of 1131-labelled thyroid hormones in the hypophysis and brain of the rabbit.

The distribution and metabolism of thyroid hormones in the brains and the hypophyses of normal rabbits was determined after intravenous administration of I131-labelled triiodothyronine or thyroxine. Triiodothyronine concentrated in the gray matter of the brain, principally in the region of the paraventricular nucleus and the median eminence, and, more heavily, in the hypophyseal lobes. The pattern of distribution of thyroxine was similar, but concentration was much less intense. Very little activity was detected in the adenohypophysis, although the existence of an extravascular thyroxine space there was determined. Triiodothyronine rapidly left the plasma, but uptake in the tissues was slower, reaching a peak after about two hours. This pattern of concentration in time may have been dependent on the formation of a previously postulated plasma-triiodothyronine complex as a precursor of the tissue triiodothyronine. It resulted in high concentration gradients between tissues and plasma. Levels as high as 75:...

THE FUNCTION OF THE THYROID IN EUTHYROID PATIENTS WITH EXOPHTHALMOS

In the presence of severe exophthalmos it has been known that the basal metabolic rate, serum concentration of protein-bound iodine, and radioiodine uptake may be normal or compatible with either hypo- or hyperthyroidism. These findings have defied the clinician to relate exophthalmos directly to thyroid function. However, in a recent study of ten clinically euthyroid patients, Werner (1955) found all tests of function normal except for suppression of uptake by administration of triiodothyronine; here the patients with exophthalmos responded like thyrotoxic patients in that their uptake was not suppressed. In an attempt to elucidate further the function of the thyroid gland in clinically euthyroid patients with exophthalmos, eight such patients have been studied. Measurements included basal metabolic rates, serum concentration of protein-bound iodide (PBI), uptake of I131 by the thyroid, and the conversion ratio of I131 in serum (PBI131). Paper chromatographic analyses were made of the serum

Note on the effects of thyroidectomy and thyroid hormone administration on the concentration of bile cholesterol and cholic acid.

SUMMARY The diminished cholesterol concentration in bile obtained after thyroidectomy, previously demonstrated by Rosenman, Friedman &amp; Byers [1951], has been confirmed, but an increased concentration after chronic administration of triiodothyronine (T3) or triiodothyroacetic acid (TA3) could not be demonstrated. The blood and bile cholesterol concentrations were not affected by large single doses of T3 or TA3. Secretion of biliary cholic acid was reduced after thyroidectomy and by prolonged administration of T3 or TA3. A low iodine diet had the same effect as thyroidectomy on the concentrations of bile cholesterol and cholic acid.

Studies in nonmyxedematous hypometabolism. II. Turnover of I131-labeld thyroxine after intravenous infusion.

THE term “euthyroid hypometabolism,” has been utilized to describe a group of patients having basal metabolic rates below −20 per cent in association with a variety of clinical symptoms suggestive of hypothyroidism but in whom other customary parameters of thyroid function are within normal limits. The concept that the low metabolic rate might be the result of a defect in the peripheral metabolism of thyroxine received support from our experience in the treatment of such patients with triiodothyronine or with mixtures of triiodothyronine and thyroxine (1, 2). In each of 4 cases, the basal metabolic rate was persistently elevated following the oral administration of triiodothyronine, alone or with thyroxine, although equivalent doses of desiccated thyroid had been ineffective. Previous studies in such patients failed to reveal any abnormality of thyroidal function as measured by the serum levels of protein-bound iodine and cholesterol, or by the 24-hour thyroidal uptake of I131. With the availability of I131-labeled l-thyroxine, it became possible to investigate more directly the peripheral metabolism of thyroxine. The utility of this technique has been demonstrated (3, 4) in a small number of subjects with normal thyroid function, hyperthyroidism, myxedema, panhypopituitarism and hypermetabolism without thyroid disease, but no such data are available in patients with euthyroid hypometabolism. The present communication reports the results of preliminaiy experiments designed to study the peripheral metabolism of thyroid hormone in patients with this syndrome.

Enhancement by triodothyronine of response to corticotrophin in anterior hypopituitarism.

SUMMARY Changes in response of the adrenal cortex to corticotrophin caused by the simultaneous intravenous administration of tri-iodothyronine have been studied in two patients with anterior pituitary insufficiency. Tri-iodothyronine caused increases in urinary excretion of ketogenic steroids and in plasma hydrocortisone. Blood eosinophils fell sharply. In addition, changes in sodium and potassium balance, and fasting blood sugar levels were observed which were consistent with increased activity of the adrenal cortex. Rapid changes in b.m.r., serum creatine and blood cholesterol were those known to be produced by tri-iodothyronine alone; so, to a large extent, was the increased negative nitrogen balance.

Interrelation of insulin activity and thyroid function.

The effect of variation in thyroid status on insulin metabolism and glycogen synthesis has been studied in rats. In vitro incubation of rat diaphragm with 0.1 mg triiodothyronine or 0.1 mg thyroxine for 30 and 45 minutes had no effect on I131 insulin uptake of the diaphragm. Daily intraperitoneal injections of 50 γ triiodothyronine increased the oxygen consumption and had an increasing effect on in vitro insulin diaphragm uptake, beginning after 2 days, reaching a maximum of 32% over controls on the 5th day. With continued administration of triiodothyronine diaphragm insulin uptake declined to control levels on the twelfth day of triiodothyronine administration. During the first 2 minutes after intravenous administration of I131 insulin in triiodothyronine treated animals (50 γ daily, i.p. for 5 days) muscle showed an increased uptake of insulin. There was a subsequent progressive fall in tissue uptake to approximately levels found in control animals. Blood radioactivity disappeared more rapidly after injection in the thyrotoxic animal than in the control or hypothyroid rats. Glycogen deposition (insulin-glycogen effect) in the thyrotoxic animals was greater than in controls. However, while tissues from control animals continued to deposit glycogen at the same rate, the diaphragm from thyrotoxic rats showed after 30 minutes of incubation a marked fall in glycogen synthesis. Glycogen synthesis by diaphragm from triiodothyronine treated animals incubated in glucose alone without insulin equilibration was the same as control diaphragm.

Effect of phosphate in enhancing the action of triiodothyronine.

IT HAS been reported from our laboratories that the intravenous administration of triiodothyronine (T-3) to a myxedematous patient was followed by a marked rise in oxygen consumption within seven hours. The intravenous administration of triiodothyronine in comparable, or even greater doses, to intact dogs has not in our hands been observed to cause any acute elevation in oxygen consumption. However, during the course of studies in dogs designed to determine the effect of triiodothyronine on the oxygen consumption of kidney tissue, it was observed that the intravenous administration of triiodothyronine to animals receiving a continuous infusion of phosphate produced a marked and rapid increase in oxygen consumption and death from what appeared to be a thyroid storm. These observations suggested that a phosphate load enhanced the action of this thyroid hormone.

Effects of in vitro administration of thyroxine and triiodothyronine on surviving liver slices.

Liver slices from frog, turtle, guinea pig, greyhound and man were incubated in Krebs-Ringer-Phosphate medium and their oxygen uptake determined manometrically. The addition of l-thyroxine or l-triiodothyronine to the suspension medium did not produce an increased oxygen consumption.