Protein-bound Iodine Concentration Research Articles

Age-dependent thyroid absorbed doses for radiobiologically significant radioisotopes of iodine.

In light of the post-Chernobyl increase in pediatric thyroid cancer incidence, among other recent events, there is renewed interest in radioiodine thyroid dosimetry and effects. Among the radioiodines produced in fission of 235U, only 131I [(T1/2)p = 8.04 d], 132I (2.3 h), 133I (20.3 h), and 135I (6.7 h) may undergo significant environmental dispersion. Age-dependent thyroid absorbed dose estimates for these radiobiologically significant radioiodines and for the "medical" radioisotopes 123I (13.2 h) and 125I (60 d) have been derived, incorporating the effect of absorption following inhalation or ingestion. This effect has generally been ignored in previously derived estimates of radioiodine absorbed doses to the thyroid. Based on the latest ICRP lung and gut models, inhaled radioiodine is absorbed at a rate of 0.175 h(-1) and exhaled at 0.101 to 0.118 h(-1) (depending on age) and ingested radioiodine is completely absorbed in the stomach at a rate of 1 h(-1). Whole-body compartmental models (SAAM II) were fit to previously published 24-h thyroid uptakes, thyroid half-times, and 48-h plasma concentration of protein-bound iodine. The resulting fitted models were used to calculate thyroid residence times of radioiodine. The mean thyroid absorbed doses [cGy/37 kBq (rad/microCi) injected intravenously] were then calculated using the age-dependent S(thyroid<--thyroid) factors (MIRDOSE III), with the highest doses (from 0.49 for 123I to 36 for 131I) in newborns and the lowest doses (from 0.014 for 123I to 1.4 for 131I) in adults in inverse relation to the thyroid mass. Although the thyroid absorbed dose for inhalation is substantially (30 to 70%) less than that for injection for all radioiodines and at all ages, it is markedly (25%) less for ingestion only for short-lived 132I.

Simplified measurement of protein-bound iodine with epithermal neutron activation analysis

A refined method for the measurement of protein-bound iodine (PBI) in blood serum was demonstrated by the use of epithermal neutron activation analysis (ENAA). PBI in ammonium sulfate-precipitated serum protein, after epithermal neutron activation, was determined by high resolution γ-ray spectrometry. From our results, the PBI concentration was 67.8 ± 2.2 ng/mL. Good agreement was obtained with published data, ranging from 40 to 80 ng/mL, which had been obtained using different analytical techniques. The validity of these techniques for PBI has been born out by a very good accuracy and simplicity without temperature dependence.

In-Patient Treatment of Chronic Varicose Venous Ulcers. A Randomized Trial of Cadexomer Iodine versus Standard Dressings

A total of 67 patients with treatment resistant chronic venous ulcers were admitted to hospital for 6 weeks of bed rest and daily dressings. The patients came from a rural area in Poland with poor socioeconomic conditions. They were randomized to treatment with either standard dressings or with cadexomer iodine. After 6 weeks all but four patients had shown a clear reduction of ulcer area; the mean reduction was 54% within the former group and 71% with cadexomer iodine. The latter treatment was significantly more effective than the standard hospital dressings in debriding the ulcer, accelerating healing and reducing pain. Elevation of serum concentrations of protein-bound iodine occurred after treatment with cadexomer iodine in patients with large ulcers, but tests of thyroid function showed no changes associated with the use of cadexomer iodine. It is concluded that cadexomer iodine significantly accelerates the healing of chronic, infected, treatment-resistant, venous ulcers in hospitalized patients.

Plasma marking of arctic foxes with iophenoxic acid.

Six arctic foxes (Alopex lagopus) were marked with iophenoxic acid (IA), a substance which elevates concentrations of protein-bound iodine in blood plasma. Buccal absorption of IA was determined by placing 20 mg IA dissolved in 100% ethyl alcohol on the tongue. Blood samples collected from 1 to 36 wk following exposure showed that all foxes were marked already at 1 wk and continued until 13 wk; two foxes were still marked at 36 wk. Clearance rates for iodine varied with initial dose response, and those foxes with high 1-wk iodine concentrations excreted iodine more rapidly than those with lower initial concentrations; by 13-wk excretion rates were similar.

A 7-month study of ingestion of sodium cyclamate by human volunteers

Men given daily doses of up to 16 g of Na-cyclamate in colored capsules for as long as 213 days suffered no untoward effects during the study other than softening of the stool. This change occurred in two of eight men given 10 g/day of Na-cyclamate and in seven of eight men given 16 g/day; it appeared in none of eight men given 5 g/day of Na-cyclamate. All men who ingested Na-cyclamate excreted cyclohexylamine in their urines on one or more occasions. Administration of Na-bicarbonate or ammonium chloride with Na-cyclamate did not influence urinary excretion of cyclohexylamine. Apparent increases in the concentration of protein-bound iodine within the bloods of men given Na-cyclamate were found to be artifacts arising from iodine in the material used to color the capsules. The results of the study are believed to indicate that any daily dose of Na-cyclamate that can be ingested by human beings without the production of diarrhea will not be injurious to the individuals during the period of ingestion.

The influence of dietary iodine on iodine in the blood serum of cows and calves in the perinatal period

Concentrations of total iodine (TI) and protein-bound iodine (PBI) in the blood serum of both cows and their neonatal calves were related to the iodine content of the diet fed to the cows. A group of six cows (group 1) fed a diet containing 0.6 ppm iodine had mean concentrations of TI and PBI of 4.1 and 3.4 microgram/100 ml respectively. A second group (group 2), fed a diet containing 4.6 ppm iodine, had concentrations of 33.8 and 7.6 microgram/100 ml of TI and PBI respectively. Calves of groups 1 and 2 had mean concentrations of TI of 21 microgram/100 ml and 96 microgram/100 ml respectively within 24 h of birth, but these concentrations declined markedly over a period of eight days. Evidence was obtained that the high concentrations of TI, and also of PBI, in neonatal calves relative to the concentrations in their dams resulted mainly from placental transfer rather than from the ingestion of colostrum.

4 Investigation and treatment of hypothyroidism

INVESTIGATION The investigation of patients with suspected hypothyroidism falls naturally into two stages. Preliminary investigation is required to determine the level of thyroid function and confirm, or refute, a clinical diagnosis of thyroid failure, and the use of other diagnostic procedures is required to identify the cause of hypothyroidism in some patients. Tests to Determine the Level of Thyroid Function The laboratory techniques available for assessing the level of thyroid function fall into three groups and the use of each allows different aspects of impaired thyroid function to be defined. The three groups of techniques are: tests of thyroid function; tests of peripheral tissue function; and tests of hypothalamic--pituitary function. The techniques have been reviewed in detail elsewhere (Evered, 1974, 1976). Tests of thyroid function Direct or indirect techniques for measuring circulating thyroid hormone concentrations have been widely available for many years. Serum thyroxine (T4) concentration may be measured by a competitive protein binding assay (Murphy, 1965) or by radioimmunoassay (Mitsuma et al, 1972). These procedures measure total serum T4 concentration, and thus alterations in thyroxine-binding globulin (TBG) capacity (e.g. pregnancy, oral contraceptive therapy, liver disease, etc.) may lead to total hormone concentrations which are at variance with the clinical assessment of the patient. The serum T4 concentration can, however, be corrected for changes in TBG by carrying out a thyroid hormone binding test (e.g. T3 resin uptake, T3 Sephadex uptake), which will estimate residual TBG capacity and may be used to calculate a free thyroxine index (FTI) (Clark and Horn, 1965). The older technique of estimating the protein-bound iodine (PBI) concentration also

Effect of a variable magnetic field of industrial frequency on thyroid function and tissue thyroxine uptake in rats

The uptake of131I by the thyroid gland and of thyroxine by the tissues of various organs, and also the protein-bound iodine (PBI) concentration in the blood plasma were studied in albino rats exposed to a variable magnetic field (VMF) with an intensity of 200 Oe, of industrial frequency, for different durations and at different intervals. In resonse to exposure for 15 min the PBI level rose. With an increase in the exposure to 6.5 h and, in particular, to 24 h the PBI level and thyroxine uptake by the tissues of the testes, heart, liver, and spleen fell. In the case of repeated exposure to a VMF (up to 6.5 h daily for 5 days) a significant increase was found in the131I concentration in the thyroid, gland and the PBI level, whereas thyroxine uptake by the tissues was considerably reduced. It is suggested that the state of the thyroid function and the tissue response to thyroxine are modified depending on the duration and rhythm of exposure to a magnetic field.

Plasma Protein-Bound Iodine and Lipids in Genetically Different Types of Cattle Grazing in a Tropical Environment

The plasma concentrations of protein-bound iodine (PBI), cholesterol and phospholipid were studied in British (Shorthorn × Hereford) and zebu cross (Brahman × British and Africander × British) cattle grazing in a tropical environment. In 20-month-old cattle, plasma PBI, cholesterol and phospholipid levels were higher ( P < 0.01) in zebu cross than in British animals and higher ( P < 0.01) in females than in males. Plasma PBI levels were positively correlated ( P < 0.001) with both cholesterol and phospholipid levels. Within sexes, the lipid level at a given PBI level was higher in zebu cross than in British animals. In pregnant cows the correlations between PBI and cholesterol levels were significant ( P < 0.001) but the relationship was negative in British animals. There were significant correlations between blood parameters of dams and birth-weight of calf in the British and Brahman-cross breeds. The results emphasize the importance of taking account of breed and sex differences when studying the blood chemistry of cattle in tropical areas.

Thyroxine and protein-bound iodine concentrations in plasma of the pacific hagfish, Eptatretus stouti (Cyclostomata)

1. 1. Plasma levels of thyroxine (T 4) were determined by competitive protein-binding analysis and compared with plasma concentrations of protein-bound iodine (PBI). 2. 2. Measurements were made on samples from normal, hypophysial-Lesioned and sham-operated fish. 3. 3. In normal animals, which had been held in the laboratory for 3 weeks, the measured T 4 values ranged from 2 to 3 μg/100 ml of plasma and PBI levels varied from 5 to 8 μg/100 ml. 4. 4. T 4 concentrations were significantly lower in both the hypophysial-Lesioned and sham-operated fish which had been maintained in the laboratory for 18 weeks. 5. 5. PBI levels tended to be lower in the experimental fish than in normal animals, but the differences were not significant. 6. 6. In both normal and experimental hagfish, thyroxine iodine comprised less than one-third of the plasma content of organic iodine.

The Influence of Fatty Acids on Serum Thyroxine Determination by Competitive Protein-Binding Radioassay

Thyroxine concentration, determined by competitive protein-binding radioassay (T4(D)), increased in serum stored at 20 degrees C and 37 degrees C. The increase correlated well with the increase in nonesterified fatty acids (NEFA). In vitro addition of NEFA to serum and in vivo increase in NEFA induced by post-prandial heparin injection resulted in a proportional increase in T4(D) values. Protein-bound iodine and thyroxine concentration, as determined by radioimmunoassay, were not influenced by storage and changes in NEFA concentration. NEFA interfere with T4(D), leading to elevated results.

RELEASE OF THYROXINE FROM THE LIVER DURING ANAESTHESIA AND SURGERY

During relatively minor surgical procedures under halothane anaesthesia, an increase in plasma protein-bound iodine concentration was observed. In patients previously given thyroxine labelled with radio-iodine, plasma radioactivity concentrations also increased. There was a concomitant decrease in radioactivity in the liver. The results suggest that anaesthesia leads to a progressive discharge of protein-bound thyroxine from the liver into the plasma. The effect is believed to be reversible.

Augmentation of the peripheral metabolism of L-triiodothyronine and L-thyroxine after acclimation to cold. Multifocal stimulation of the binding of iodothyronines by tissues.

Increased metabolism of thyroid hormones was observed in rats adapted to an ambient temperature of 4 degrees C. The increased hormonal degradation was manifested in enhanced metabolic, urinary deiodinative, biliary, and fecal clearances of iodothyronines. Increased metabolic clearances were due to stimulation of cellular hormonal disposition, evidenced by elevated intrinsic cellular clearances. After adaptation, the concentration of protein-bound iodine in plasma was decreased, and the binding of the hormones by plasma proteins was increased. The enhanced rate of metabolism of iodothyronines was associated with stimulation of the binding of these hormones by diverse tissues, suggesting the participation of extrahepatic degradative foci in the increased hormonal deiodination observed in vivo. Increased hepatocellular binding and a significantly enlarged hepatic distribution space of thyroxine were noted. Hepatocellular binding of triiodothyronine was similarly augmented, and a smaller but significant increase in the hepatic space of this iodothyronine was detected. Analysis of the hepatic subcellular partition of iodothyronines 35 min after the intravenous administration of isotopically labeled thyroid hormones disclosed increased hormonal binding by the microsomal fraction in cold-adapted animals and an attendant increase in the microsomal protein concentration. Partial microsomal subfractionation in a discontinuous sucrose gradient indicated that the observed stimulation of microsomal hormonal binding was associated with proliferation of the smooth endoplasmic reticulum.

Some nutritional implications of group-feeding hill sheep

SUMMARYIn the first experiment two groups of 11 Scottish Blackface ewes were given either 6·10 kg dried grass pellets plus 1·63 kg chopped dried grass daily (Group A) or 8·17 kg hay plus 1·32 kg oat pellets (Group B). During a 10-day experimental period individual dry-matter intakes ranged from 484 to 939 g/day (CV 22·3%) in Group A and from 613 to 883 g/day (CV 13·3%) in Group B. In Group B dry-matter intakes from oats were much more variable (10 to 149 g/day; CV 35·8%) than those from hay (530 to 762 g/day; CV 12·9%). Plasma protein-bound iodine (PBI) concentrations were significantly higher in the Group A sheep.In the second experiment the treatments were: group-penned, group-fed (GG); group-penned, individually fed (GI); and individually penned, individually fed (II). Within each treatment there were two groups of 12 ewes; one group was given a high level of feeding (H) and the other a low level (L) for a 7-week experimental period. Allowances of pelleted concentrates ranged from 7 to 15 g/kg in the L groups and from 18 to 26 g/kg in the H groups. The same mean quantities per kg were given to GG sheep, and food intakes ranged from 5·7 to 17·7 g/kg (CV 25·3%) in GGL and from 12·5 to 30·8 g/kg (CV 24·8%) in GGH. Plasma PBI concentrations were significantly higher in L sheep than in H sheep, and higher in GG than in II. Plasma non-esterified fatty acid concentrations were significantly higher in L sheep than in H sheep and higher in GG than in GI and II.The principal factors determining variations in food intakes between individual animals fed in groups and some of the nutritional implications of group-feeding sheep are discussed.

CONGENITAL EUTHYROID GOITRE AND PARTIAL PERIPHERAL RESISTANCE TO THYROID HORMONES

A woman aged 25, who had had goitre at birth and had undergone thyroidectomy twice for non-toxic goitre during childhood, was entirely euthyroid. Concentrations of protein-bound iodine, total and free thyroxine, and total triiodothyronine were about twice the normal upper level, and the daily turnover of thyroxine was about doubled, but the level of thyrotrophin in the blood and the responses of thyrotrophin-stimulating hormone and triiodothyronine to stimulation with thyrotrophin-releasing hormone were normal. These findings are compatible with partial resistance to thyroid hormones in the peripheral tissues, including the anterior pituitary. The syndrome differs from the peripheral resistance described by other workers, with deaf-mutism, delayed bone development, and stippled epiphyses. It thus represents a different type of unresponsiveness to thyroid hormones.

Accelerated cellular uptake and metabolism of L-thyroxine during acute Salmonella typhimurium sepsis.

The effects of acute Salmonella typhimurium sepsis on the kinetics of peripheral L-thyroxine (T(4)) distribution and metabolism and on serum total and free T(4) concentrations were studied in rhesus monkeys inoculated i.v. with either heat-killed or viable organisms. The rate of disappearance of labeled T(4) from serum was increased within 8 h after inoculation of monkeys with either heat-killed or viable Salmonella. The effects of the heat-killed organisms were transient and no longer evident by 16 h postinoculation. The monkeys inoculated with the viable Salmonella experienced a 2-3 day febrile, septic illness that was accompanied by an increase in the absolute rate of T(4) disposal. In the infected monkeys, serum total T(4) and endogenously labeled protein-bound iodine concentrations fell significantly during the period of acute sepsis and then rose during convalescence to values that exceeded the preinoculation values, suggesting that thyroidal secretion of hormone had increased in response to a primary depletion of the peripheral hormonal pool. Total cellular and hepatic uptakes of T(4) were enhanced by 4 h after inoculation of monkeys with either heat-killed or viable Salmonella, but the increase in total cellular uptake persisted for 24 h only in the monkeys inoculated with the viable organisms. These alterations in T(4) kinetics could neither be correlated with changes in the binding of T(4) in plasma nor attributed to an increase in vascular permeability. Moreover, they could not be ascribed to an in vitro product of bacterial growth, suggesting that the presence of the organisms themselves was required. An acceleration of T(4) disappearance was also observed during Escherichia coli and Diplococcus pucumoniae bacteremias. Our findings are consistent with a primary increase in the cellular uptake and metabolism of T(4) during bacterial sepsis, possibly related to phagocytic cell function in the host.

Serum triiodothyronine concentration in the iodine‐deficient rat

AbstractA low iodine diet fed to rats resulted in decreased absolute amounts of circulating triiodothyronine and protein‐bound iodine (PBI), but an increase in the triiodothyronine: protein‐bound iodine ratio. Since baseline protein‐bound iodine values were high, it is possible the “normal” diet fed was in fact a high iodine one. In this event, the fall in protein‐bound iodine with the low iodine diet would be greater than that in thyroxine concentration. The relative increase in triiodothyronine compared to PBI concentration with the low iodine diet could result from preforential synthesis and secretion of triiodothyronine by the iodine‐deficient thyroid; or could be due to accelerated removal of thyroxine due to increased peripheral utilization. Either change could keep body metabolism normal or nearly so over an extended period of iodine want.

Protein-Bound Iodine and Protein Concentration in Plasma and Pericardial Fluid of Metamorphosing Anuran Tadpoles

Protein-Bound Iodine and Protein Concentration in Plasma and Pericardial Fluid of Metamorphosing Anuran Tadpoles

Effects of chronic excess salt feedin: demonstration of normal thyroid function in salt-fed dogs with hypercholesterolemia.

SummaryThe hypercholesterolemia associated with chronic excess salt feeding is not due to hypothyroidism. As shown by thyroidal 131I uptake, by plasma protein-bound iodine concentrations, and by hi...

Thyroglobulin-like substances with low iodine content in the serum of patients receiving antithyroid therapy.

ABSTRACT Serum from 47 treated hyperthyroid patients was investigated for thyroglobulin using a “reversed” hemagglutination technique with erythrocytes coated with a highly purified thyroglobulin antibody. Thyroglobulin activity was demonstrated by this means in the serum of only 2 out of 18 patients who had previously undergone subtotal thyroidectomy, but in the serum of 11 out of 18 patients who were receiving antithyroid drugs [including 10 out of the 11 receiving methylthiouracil (MTU)] and in that of 5 out of 11 patients who had previously received antithyroid drugs. Experiments using Sephadex filtration and ultracentrifugation in sucrose gradient would suggest that the agglutinating substance in the serum of patients receiving MTU has a molecular weight of the same order as that of thyroglobulin, but the serum concentrations of protein-bound iodine (PBI) revealed that the iodine content of this thyroglobulin-like substance must—at least in some cases—be considerably lower than that normally found in...