The contribution of thyroxine-binding prealbumin to the binding of thyroxine in human serum, as assessed by immunoadsorption.

An immunoadsorption technique employing a rabbit antiserum specific for human serum prealbumin has been devised to remove thyroxine (T(4))-binding prealbumin (TBPA) from serum completely without affecting the T(4)-binding activity of thyroxine-binding globulin (TBG) or the concentration of the other major proteins in serum. As judged from the proportion of T(4) associated with the antigen-antibody precipitate, only about 15% of the endogenous T(4) is bound by TBPA, a value considerably less than that indicated by electrophoretic methods. As judged from the increase in the proportion of free T(4) that followed immunoadsorption of TBPA, TBPA does act as one determinant of the proportion of free T(4) but is far less important than TBG in this respect. A decrease in the T(4)-binding capacity of TBPA cannot solely account for the increase in the proportion of free T(4) in the sera of ill patients, since a comparable increase does not occur in normal sera after complete removal of TBPA. From data obtained in normal and abnormal sera before and after immunoadsorption of TBPA, estimates of the equilibrium constants for the interactions between T(4) and its binding proteins, as they exist in serum, have been derived. The values obtained were: K(ALB), 6.2 x 10(5); K(TBPA), 2.3 x 10(8); and K(TBG), 1.7 x 10(10).

Observations on the maturation of thyroid function in early fetal life.

Serum samples were obtained from 21 normal human fetuses after therapeutic abortion for psychiatric indications. Fetal crown-rump length ranged from 5.2 to 22.5 cm, corresponding to the gestational age of 65-168 days.Serum thyroxine, assayed by a modification of the Murphy-Pattee method, was identified in the second smallest fetus examined at 78 days gestation. Thereafter it increased rapidly, maintaining a significant linear correlation with crown-rump length until term (r = 0.800, P < 0.001). Free thyroxine (FT4) also increased in a linear relation to gestational age (r = 0.908, P < 0.001), but reached term levels by 18-20 wk. Radioimmunoassayable thyroid-stimulating hormone (TSH) was detected at 78 days gestation. Levels increased rapidly with advancing gestation, so that by 16 wk almost all were within the range of term infants. After 16 wk gestation, levels were usually greater than 4.0 muU/cc, higher than that seen in normal children. No correlation was demonstrated between the serum TSH levels and total thyroxine. TSH and FT4, however, increased in a parallel manner with a significant positive correlation. This suggested that fetal TSH secretion was responsive to FT4 levels from very early in gestation, possibly as early as 11 wk.Thyroxine-binding globulin (TBG) was detected in a fetus of 78 days gestation (1.4 mug/100 ml). Levels increased rapidly, paralleling the rise in serum thyroxine and maintaining a linear correlation with crownrump length (r = 0.864, P < 0.001). Thyroxine-binding prealbumin binding capacity (TBPA) in fetuses 14-24 wk gestation was comparable with that seen at term. When examining the distribution of tracer amounts of thyroxine-(131)I (T4-(131)I) between the thyroxine-binding proteins, it was found that a major fraction was bound to TBPA and albumin during the early part of gestation. This decreased linearly with maturation of the fetus as the fraction bound to TBG increased. By 20 wk gestation fetal TBG was able to bind 78% of tracer despite a TBG capacity of only 7.7 mug/100 ml. This appeared to be the result of relatively low concentrations of TBPA and albumin during this period of gestation. The theoretical association constant calculated for fetal and newborn TBG was found to be similar to that estimated for normal adult males and females.

Relative rates of transcapillary movement of free thyroxine, protein-bound thyroxine, thyroxine-binding proteins, and albumin.

The rate of appearance of labeled thyroxine (T4) and albumin in lymph from various areas after simultaneous i.v. injection of the labeled substances in conscious ambulatory sheep has been used to estimate the relative rates of transcapillary movement of stable T4 and albumin. Labeled T4 appeared in hepatic lymph at the same rate as albumin. In intestinal and leg lymph, labeled T4 appeared eight and four times as rapidly as albumin indicating that T4 crosses capillaries in these areas independently of and much more rapidly than albumin and other proteins having similar distribution kinetics. The lymph:plasma ratios for all the T4-binding proteins including albumin were very similar in any one area showing that the relative fractional rates of transcapillary movement of these proteins were very similar. Therefore in extrahepatic areas, transcapillary movement of T4 in the protein-bound form was quantitatively much less important than in the free form. The findings support earlier views, recently questioned, that free T4 is of considerable physiological significance.

Serum triiodothyronine: measurements in human serum by radioimmunoassay with corroboration by gas-liquid chromatography.

Serum triiodothyronine (T(3)) has been measured by radioimmunoassay and corroborated by analysis of the identical samples with a previously described gas-liquid chromatographic technique. Special features of the radioimmunoassay procedure which permit determinations in unextracted serum include the use of a T(3)-free serum preparation for the construction of the standard curve and of tetrachlorothyronine to inhibit binding of T(3) to thyroxine-binding globulin.T(3) values by radioimmunoassay were 138 +/-23 ng/100 ml (mean +/-SD) in 82 normal subjects, 62 +/-9 ng/100 ml in 45 hypothyroid patients, and 494 +/-265 ng/100 ml in 60 patients with toxic diffuse goiter. In the hypothyroid group, the range was similar in patients with both primary and secondary hypothyroidism. There was no overlap between the three thyroidal states. Elevated T(3) levels were seen in 40 cases that appeared clinically hyperthyroid but had normal serum thyroxine (T(3)) determinations, a syndrome we have called T(3) toxicosis. Values obtained with radioimmunoassay agreed closely with those we had previously found by gas-liquid chromatography which were 68 +/-2 ng/100 ml in hypothyroidism, 137 +/-23 ng/100 ml in normal subjects, and 510 +/-131 ng/100 ml in untreated toxic diffuse goiter. Since T(3) is very potent and its level varies in different clinical states, accurate T(3) measurements are required to assess a patient's thyroid status properly. The radioimmunoassay for T(3) appears to be sufficiently sensitive, precise, and simple to permit its routine clinical application for this purpose.

Thyroid hormone binding by human serum prealbumin (TBPA). Electrophoretic studies of triiodothyronine-TBPA interaction.

Thyroxine-binding prealbumin (TBPA) in normal human serum has been shown in a polyacrylamide gel electrophoresis system to bind 7-9% of tracer level purified [(125)I]triiodothyronine (T3), and more than 30% of T3 in serum deficient in thyroxinebinding globulin (TBG). The T3-TBPA interaction has been confirmed at pH 9.0 and pH 7.4 in this electrophoretic demonstration of TBPA binding of T3 in serum. Purified human TBPA has also been shown to bind T3. Progressive additions of unlabeled thyroxine (T4) to serum containing tracer [(125)I]T3 displace T3 from TBG, its principal carrier, to TBPA and albumin; however, T4 loading does not lead to significant T3 displacement from TBPA even at T4 levels known to saturate TBPA. Loading of serum with unlabeled T3 results in displacement of more than 50% of [(125)I]T3 from TBPA, as well as from TBG, to albumin. Studies carried out with serum containing diphenylhydantoin (DPH) or MK-185, known inhibitors of T4 binding by TBG, also showed T3 displacement from TBG to TBPA and albumin. Although salicylate and tetraiodothyroacetic acid (TETRAC) displace T4 from sites on TBPA, they have only minimal effects on T3-TBPA interaction.

Measurement of circulating desialylated glycoproteins and correlation with hepatocellular damage.

Addition of increasing amounts of (125)I-labeled desialylated thyroxine-binding globulin (DTBG) to hepatic cell membranes resulted in a progressive increase in binding. Saturability of membrane sites was indicated by a concentration beyond which further increases in [(125)I]DTBG resulted in no further binding. The binding curve for [(125)I]DTBG was similar to binding curves of desialylated orosomucoid, fetuin, and ceruloplasmin. An inhibition assay system using hepatic cell membranes showed that desialylated orosomucoid had a greater affinity for membrane binding sites than did DTBG but desialylated fetuin and ceruloplasmin bound less avidly than DTBG. Serum from normal persons and patients with a variety of illnesses was tested for its ability to inhibit [(125)I]DTBG binding. The inhibitory activity of 1 ml of normal serum was equivalent to that of 0.2-2 mug DTBG. Patients with Laënnec's cirrhosis, biliary cirrhosis, and hepatic metastases had greatly increased inhibitory activity in their serum. Patients with jaundice due to extrahepatic obstruction had inhibitory activity not significantly different from that found in normal serum. Column chromatography of normal serum on Sephadex G-200 resulted in inhibitory activity throughout the range of protein molecular weight. Desialylation of normal serum with neuraminidase enhanced the inhibitory activity but did not change the distribution of the activity. Gel chromatography of cirrhotic serum showed markedly increased inhibitory activity associated with the macroglobulins and the 4.5S peak and a new peak of inhibitory activity in the low molecular weight area was also seen. Inhibition of desialylated glycoprotein binding to liver cell membranes by serum from patients with hepatocellular disease raises the possibility that desialylated serum glycoproteins accumulate in the circulation and that patients with compromised hepatocellular function may no longer be able to clear them from the circulation. Alternatively, accumulation of desialylated glycoproteins in the circulation could result from defective protein synthesis by the diseased liver.

Removing substances from blood by affinity chromatography. I. Removing bilirubin and other albumin-bound substances from plasma and blood with albumin-conjugated agarose beads.

Substances such as bilirubin that bind tightly to plasma proteins cannot readily be removed from blood. We describe here the use of affinity chromatography as a new approach to the removal of proteinbound metabolites and toxins from blood. Agarose beads were coupled via cyanogen bromide to human serum albumin so as to contain 30-50 mg of albumin/g wet wt. Such beads, when exposed to plasma from a patient with congenital nonhemolytic jaundice labeled with [(14)C]-bilirubin, bound more than 150 mug bilirubin/g of beads. The binding was saturable, concentration-dependent, relatively independent of flow rate, and reversible by elution with plasma, albumin, or 50% (vol/vol) ethanol. The beads could be repeatedly reused without loss of efficiency after ethanol elution and long storage in the cold. Salicylate, cortisol, and taurocholate, which bind weakly to albumin, were retarded by the beads but eluted with neutral buffer. Thyroxine, taurolithocholate, chenodeoxycholate, and digitoxin bound tightly but were eluted with 50% ethanol. Digoxin did not bind at all. When whole blood was passed over agarose-albumin beads, bilirubin was removed, calcium and magnesium fell slightly, but red cells, white cells, platelets, clotting factors, and a variety of electrolytes and proteins were substantially unchanged. Agarose-albumin beads may be useful for removing protein-bound substances from the blood of patients with liver failure, intoxication with protein-bound drugs, or specific metabolic deficits. Furthermore, it may be possible to make useful adsorbents by attaching other proteins to agarose or other polymer beads.

Carbamazepine and thyroid function in affectively ill patients. Clinical and theoretical implications.

Thyroid function was examined in 50 affectively ill patients before and four weeks after carbamazepine treatment. Carbamazepine significantly and substantially decreased peripheral thyroid hormone levels while increases in thyrotropin levels, although significant, were of much smaller magnitude. Furthermore, the decreases in levels of thyroxine (T4) and free T4 were significantly greater in carbamazepine responders than in nonresponders. These findings are discussed in light of current theories of the role of the thyroid axis in affective illness.

Seasonal changes in serum thyroid hormone binding proteins in the woodchuck (Marmota monax).

To evaluate the role of serum T4- and T3-binding proteins in the elevation of serum T4 and T3 concentrations in the woodchuck in the fall and winter, blood was collected from woodchucks during the four seasons of the year (seasonal study) and from 2-week fasted woodchucks in the summer (fasting study) and the serum concentrations of total T4 and T3 were measured. The distribution of [125I]4 and [125I]T3 tracers among the serum binding proteins and the serum T4-binding globulin (TBG) binding capacity for T4 was determined by polyacrylamide gel electrophoresis. Plasma concentrations of both T4 and T3 were highest in the winter. The major T4-binding protein in the woodchuck is TBG. There was an increase in both [125I]T4 and [125I]T3 tracer binding to serum TBG in fall and winter, and TBG binding capacity for T4 was 2-fold higher in winter than in summer. There were increases in TBG binding and in the TBG T4 binding capacity in the 2-week starved animals. The increased binding of T4 and T3 by TBG in the fall and winter may be partially responsible for the increased serum concentrations of T4 and T3 in the fall and winter in the woodchuck, a time when secretion of T4 and T3 by the thyroid gland is very low. This may be facilitated by the low or absent food consumption at these times of the year.

Relationship of oligosaccharide modification to the cause of serum thyroxine-binding globulin excess.

T4-binding globulin (TBG), a glycoprotein with four N-glycosyl complex oligosaccharide chains, exhibits sialic acid-dependent microheterogeneity on isoelectric focusing (IEF). Increasing the sialic acid content of TBG increases its anodal IEF mobility and decreases its rate of in vivo degradation, a mechanism for the elevation of serum TBG levels in pregnancy. In this study, the structure of oligosaccharides in TBG from subjects with various conditions associated with TBG excess was determined by measuring the proportion that bound to Concanavalin-A (Con-A). Since oligosaccharides with three or more branches (antennae) attached to the trimannosyl core are excluded from binding to Con-A, the percentage of serum TBG not bound to Con-A (% peak A) represented the portion of TBG molecules with three or more antennae in all oligosaccharide chains interacting with Con-A. Peak A contained the most anodal IEF bands, while the Con-A-bound TBG (peak B) contained the cathodal bands. Serum samples from 10 normal men and 10 premenopausal women did not significantly differ in terms of TBG levels, % peak A, or IEF mobility and were combined as a single group (normal). Eight subjects with elevated serum TBG levels due to inherited TBG excess [62.0 +/- 10.1 (+/- SD) mg/L] or 2 receiving 5-fluorouracil treatment (26.2 and 31.3 mg/L) compared to 20 normal (14.7 +/- 3.3 mg/L) had % peak A values and IEF mobility similar to those in normal subjects. On the other hand, high serum TBG levels in 8 women during the third trimester of pregnancy (39.2 +/- 5.3 mg/L), 2 women taking oral contraceptives (25.7 and 27.0 mg/L), and 3 women with acute hepatitis (34.8 +/- 4.8 mg/L) were associated with significant elevations of % peak A values (5.68 +/- 1.73%, 3.31% and 2.41%, and 3.25 +/- 0.78%, respectively) compared to those in normal subjects (1.33 +/- 0.40%), as well as increased anodal mobility on IEF. Treatment of a man for 3 days with ethinyl estradiol produced similar changes. Using data from densitometry measurements of IEF bands of TBG, the degree of anodal shift was quantitated (anodal index). This index correlated with the % peak A (r = 0.92) in all study subjects. We conclude that increased sites for sialylation, resulting from the increased proportions of triantennary oligosaccharide chains, account for the increased anodal mobility of TBG in hyperestrogenemia and hepatitis. Thus, in these two conditions, a reduced TBG degradation rate resulting from oligosaccharide modification is the likely mechanism of increased serum TBG levels.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of the thyroxine-binding globulin (TBG) gene in six unrelated families with complete TBG deficiency.

T4-binding globulin (TBG) is a glycoprotein of hepatic origin which transports thyroid hormone in serum. Inherited TBG defects in man are X-chromosome linked and are expressed in hemizygotes as complete deficiency, partial deficiency, or excess. Since TBG is not necessary for thyroid hormone action, affected subjects are healthy. Using DNA probes for human TBG, we searched for restriction fragment length polymorphisms in six affected males belonging to 6 unrelated families with inherited complete TBG deficiency and an equal number of normal males. TBG could not be detected in the serum of any of the TBG-deficient males by a specific and sensitive RIA capable of detecting as little as 5 micrograms TBG/L or 0.031% of the average normal serum TBG concentration. DNA isolated from white blood cells was digested with 11 restriction endonucleases, and the digests were submitted to DNA blot analysis using two cloned TBG-DNA probes which together covered the entire protein coding and the 5'-flanking sequences of the TBG gene. A total of 26 different bands were detected on DNA blots, identifying 18 restriction sites located within the 4.2-kilobase TBG gene, which includes intronic, exonic, and 5'-flanking sequences. This analysis, which sampled 2.3% of the total TBG genome, failed to reveal differences in fragment size among the 6 TBG-deficient and 6 normal males examined. One restriction endonuclease (NcoI) identified normal sequences at the putative promoter region of the gene, and four other endonucleases (TaqI, SstII, MspI, and HpaII) recognized the cytosine-guanine dinucleotide phosphate sequences representing potential mutation hot spots. Although C was methylated at these sites, no C to T (thymidine) transitions were found. These data suggest that large deletions, insertions, or rearrangements of the TBG gene, or mutations at sites of methylated cytosine-guanine dinucleotide phosphate dimers are not common mechanisms for inherited complete TBG deficiency in man.

Circadian variation of thyrotropin in childhood.

We evaluated the circadian variation of serum TSH in 96 normal children, aged 5-18 yr. Blood samples were obtained hourly for 24 h, and serum TSH was measured using an immunoradiometric assay with a sensitivity of 0.2 mU/L and an intraassay coefficient of variation of 4.9%. The nadir serum TSH value, defined by the three consecutive hourly TSH concentrations having the lowest mean, occurred between 1000 and 1900 h, while the peak TSH value, defined by the three consecutive hourly TSH concentrations having the greatest mean, occurred between 2100 and 0600 h. The mean nadir serum TSH was 1.6 +/- 0.1 mU/L, and the mean peak TSH was 3.7 +/- 0.2 mU/L. The mean nocturnal TSH surge (percent increase in TSH from nadir to peak) was 144% (95% confidence limits, 50-300%) and did not correlate with serum T4, free T4, or T3 concentrations. Seventy-six children were given TRH (7 micrograms/kg). The mean peak serum TSH after TRH was 16.0 +/- 1.1 mU/L (95% confidence limits, 9.0-42.0 mU/L), and it occurred by 30 min after TRH administration in 92% of the children. The absolute peak nocturnal serum TSH and peak post-TRH serum TSH values correlated significantly (r = 0.62; P less than 0.001), while age, gender, and pubertal status did not correlate with either the nocturnal TSH surge or the TSH response to TRH. We conclude that normal children have a circadian variation of serum TSH characterized by a nocturnal TSH surge, and that the peak of serum TSH, which occurs at night, correlates with the peak serum TSH level after TRH administration.

Normal cellular uptake of thyroxine from serum of patients with familial dysalbuminemic hyperthyroxinemia or elevated thyroxine-binding globulin.

To determine whether thyroid hormone-binding proteins in serum, particularly albumin, facilitate the transfer of T4 into human tissues, we studied cellular T4 uptake (CT4) by human liver (Hep G2) cells from medium containing serum from subjects with familial dysalbuminemic hyperthyroxinemia (FDH) and acquired and familial T4-binding globulin (TBG) excess and patients with normal T4-binding to albumin and normal TBG concentrations. Serum from nine subjects with FDH whose mean serum total T4 (TT4) concentration was 203 +/- 27 nmol/L were matched for TT4 concentrations with serum from nine subjects with acquired TBG excess (TT4, 201 +/- 23 nmol/L) and nine subjects with thyrotoxicosis and normal TBG concentrations (TT4, 205 +/- 28 nmol/L). The subjects' CT4 results were compared to their serum free T4 concentration, measured by equilibrium dialysis (DT4), and their serum free T4 index (FT4I) value. The mean serum DT4 value for the subjects with FDH (23 +/- 5 fmol/L) and those with TBG excess (23 +/- 3 fmol/L) were normal, whereas it was elevated (44 +/- 9 fmol/L; P less than 0.001) for the thyrotoxic patients with normal TBG concentrations. The mean CT4 value also was normal for the subjects with FDH (37.7 +/- 4.9 fmol/plate) and those with TBG excess (36.6 +/- 4.6 fmol/plate), but was elevated for the thyrotoxic patients (62.3 +/- 11.2 fmol/plate; P less than 0.001). In all three groups studied, the relationship between individual CT4 and DT4 values was similar to that previously found in subjects with no T4-binding protein abnormalities. The mean serum FT4I value was lower for the subjects with acquired TBG excess (111 +/- 22) than for the subjects with FDH (133 +/- 22; P less than 0.05), and it was much higher for the subjects with thyrotoxicosis (221 +/- 31; P less than 0.001). In the subjects with FDH and those with thyrotoxicosis the normal relationship between CT4 and FT4I was maintained, while in the subjects with acquired TBG excess, FT4I values were lower than expected. In seven of the nine subjects with TBG excess, the abnormality was associated with conditions known to increase its sialic acid content: hepatitis (one subject), pregnancy (four subjects), and estrogen therapy (two subjects). The CT4 values were similar in nine subjects with acquired TBG excess (seven pregnant women and two subjects with chronic active hepatitis) and five subjects with familial TBG excess (34.8 +/- 4.3 vs. 34.0 +/- 8.6 fmol/plate, respectively).(ABSTRACT TRUNCATED AT 400 WORDS)

Biological effects of various doses of conjugated equine estrogens in postmenopausal women.

To determine which dosage of estrogen might provide physiological replacement and also avoid possible harmful side effects, 21 postmenopausal women were studied before and after the oral administration of conjugated equine estrogens. The dosages studied were 0.15, 0.30, 0.625, and 1.25 mg/day, with each being given for 6 weeks. Fifteen premenopausal women were also studied, and their values were presumed to reflect normal physiological function. Variable responses of the different biochemical and biological markers of the action of estrogen were observed. Both LH and FSH levels showed stepwise decreases with increasing amounts of estrogen, but even 1.25 mg/day did not suppress these hormones to the range found in premenopausal women, suggesting a subphysiological response. The lower dosages of conjugated estrogen had minimal effects on vaginal cytology, with only the 1.25-mg dose changing the maturation index to values similar to those found in premenopausal subjects. The 0.3-mg dose of conjugated estrogen was the lowest amount that resulted in a significant reduction (P < 0.05) of the urinary calcium to creatinine ratio (an index of bone resorption). Liver protein synthesis was the most sensitive parameter to the action of estrogen. Hepatic resoponses were variable depending on which protein was assessed. These data indicate that the oral administration of conjugated equine estrogens results in inconsistent effects. All doses exerted subphysiological, physiological, and pharmacological responses at the different sites of action.

Thymulin (Zn-facteur thymique serique) activity in anorexia nervosa patients.

Thymulin (or FTS-Zn) a well-defined thymic hormone was studied in fifteen female patients hospitalized for anorexia nervosa. The circulating hormone was measured together with the plasma levels of thyroid hormones, cortisol and zinc. Thymulin activity determined by the rosette assay was significantly reduced in the anorexia nervosa patients compared to sex- and age-matched healthy control subjects. The patients were characterized by very depressed plasma levels of triiodothyronine (T3) but exhibited normal concentrations of thyroxine (T4), thyroxine-binding globulin (TBG), cortisol and zinc. The distribution of their peripheral lymphocyte cells into several subsets was not affected. The observed decrease of thymulin activity in this illness might be the consequence of thymic atrophy secondary to malnutrition and/or hormonal disturbances. Our results suggested that the fall in thymulin level might explain the variability of cellular immune responses in anorexia nervosa patients and occurrence of energy when their weight loss is far advanced.

Thyroid function and circulating antithyroid antibodies in myasthenia gravis.

Evaluation of thyroid function in 104 patients with myasthenia gravis by T3, T4, TBG, and TSH radioimmunoassays and the TRH-stimulation test in 47 patients disclosed thyrotoxicosis in 5.7%, preclinical hyperthyroidism probably due to autonomously functioning thyroid tissue in about 10% of patients stimulated with TRH, hypothyroidism in 1.9%, and preclinical hypothyroidism in 3.4%. Eighty-four percent were euthyroid. Antithyroid antibody activity was detected by hemagglutination tests. Twelve patients had antithyroglobulin antibodies (Tab), and 28 had antimicrosomal antibodies (Mab). Among the euthyroid myasthenic patients, 7 were Tab-positive and 20 were Mab-positive. Euthyroid antibody-positive patients had a significantly higher TSH response in the TRH stimulation test and may be at high risk for hypothyroidism.

Elevated thyroxine levels due to increased thyroxine-binding globulin in acute hepatitis.

Two patients are presented who had unexpected increases in serum thyroxine concentration due to acquired thyroxine-binding globulin excess associated with asymptomatic hepatitis. Serum hormone concentrations were also analyzed retrospectively in 10 outpatients with viral hepatitis. Acute hepatitis is associated with an increase in serum thyroxine and thyroxine-binding globulin concentrations and a corresponding decrease in the triiodothyronine resin uptake. In five patients, serum thyroxine concentration (mean +/- SD) was elevated at 21.08 +/- 5.86 micrograms/dl during illness, and decreased to 10.18 +/- 2.96 micrograms/dl during full recovery (p less than 0.05); serum thyroxine-binding globulin concentration was elevated at 2.14 +/- 0.36 mg/dl during illness, and decreased to 1.18 +/- 0.16 mg/dl during recovery (p less than 0.01). Interpretation of thyroid function test results can be difficult in patients with hepatitis. When serum thyroxine is elevated, careful attention to a decrease in the triiodothyronine resin uptake is essential to avoid the incorrect diagnosis of hyperthyroidism. Occasionally, this change in the triiodothyronine resin uptake may be the first evidence of occult hepatic inflammation.

Calculation of an estimate of throxine-binding globulin capacity.

An estimate of the serum thyroxine-binding globulin (TBG) may be computed from determinations of serum thyroxine and triiodothyronine uptake. A general equation for this computation is presented and a computer program for the calculation of the estimating parameters is dicussed. With these methods, the regression equation for the calculated TBG and the observed TBG is the line of identity, and the correlation coefficients from determinations on data from two laboratories were +0.88 and +0.96. The calculated TBG may be used as a screening test for abnormalities of thryoxinebinding protein and as an aid in the proper interpretation of thyroid function studies.

Laboratory assessment of nutritional status.

Malnutrition is one of the major causes of increased morbidity and mortality among hospitalized patients. The availability of nutritional therapy for these patients has made clinicians aware of the need for reliable methods of nutritional assessment. A variety of anthropometric, biochemical, and immunologic parameters has been used as indicators of protein-calorie malnutrition. Recently, the concentration of several rapid-turnover visceral proteins (transferrin, thyroxine-binding prealbumin and retinol-binding protein) has been shown to be a very sensitive parameter for indicating both the efficiency of nutritional therapy and conditions of borderline protein intake in apparently healthy children. Likewise, several immunologic parameters (including T cells, delayed hypersensitivity response, and complement components) have been shown to correlate with morbidity, mortality risk, sepsis, and death.

Evaluation of new kits for the assessment in vitro of thyroid function by determination of serum total thyroxine, free TBG capacity, and free thyroxine index Sephadex G-25 and 125I-labelled triiodothyronine and thyroxine.

A trial was carried out on 134 patients of new kits (Ames Co) using columns of Sephadex G-25 for the determination of serum total thyroxine (Tetralute test) and for the indirect estimation of serum free thyroxine-binding globulin capacity (Trilute test). Both new methods were quicker and easier than the reference resin methods and of similar precision. The two measurements when combined to give a free thyroxine index (Trilute-Tetralute-FTI) increased further the diagnostic discrimination and usefulness of the tests. The method for the determination of serum thyroxine can be modified to give a direct estimate of serum free thyroxine, expressed as a free thyroxine index. This new single-column technique, called the ;single-column free thyroxine index', gave a good correlation with clinical thyroid status in a preliminary trial of 45 patients.