Effect of therapy on serum thyroglobulin levels in patients with Graves' disease

Laboratory Thyroid Tests: A Historical Perspective

Background: This review presents a timeline showing how technical advances made over the last seven decades have impacted the development of laboratory thyroid tests. Summary: Thyroid tests have evolved from time-consuming manual procedures using isotopically labeled iodine as signals (¹³¹I and later ¹²⁵I) performed in nuclear medicine laboratories, to automated nonisotopic tests performed on multianalyte instruments in routine clinical chemistry laboratories. The development of isotopic radioimmunoassay techniques around 1960, followed by the advent of monoclonal antibody technology in the mid-1970s, led to the development of a nonisotopic immunometric assay methodology that forms the backbone of present-day thyroid testing. This review discusses the development of methods for measuring total thyroxine and triiodothyronine, direct and indirect free thyroid hormone measurements and estimates (free thyroxine and free triiodothyronine), thyrotropin (TSH), thyroid autoantibodies (thyroperoxidase, thyroglobulin [Tg] and TSH receptor autoantibodies), and Tg protein. Despite progressive improvements made in sensitivity and specificity, current thyroid tests remain limited by between-method differences in the numeric values they report, as well as nonspecific interferences with test reagents and interferences from analyte autoantibodies. Conclusions: Thyroid disease affects ∼10% of the U.S. population and is mostly managed on an outpatient basis, generating 60% of endocrine laboratory tests. In future, it is hoped that interferences will be eliminated, and the standardization/harmonization of tests will facilitate the establishment of universal test reference ranges.

Multi-center evaluation of the highly sensitive Abbott ARCHITECT and Alinity thyroglobulin chemiluminescent microparticle immunoassay

Background

Thyroglobulin (Tg) is an essential part for the management of patients with differentiated thyroid carcinoma (DTC) after thyroidectomy. Highly sensitive Tg assays are now established in clinical practice as they facilitate follow‐up of DTC patients. In this study, we evaluated the recently launched highly sensitive Abbott Tg assay for Alinity and ARCHITECT.

Methods

In this three‐center study, Tg values of 447 routine patient samples, characterized for the presence of anti‐Tg, were measured with the ARCHITECT Tg assay and compared with the Roche Elecsys TgII assay. In addition, a subset of 154 samples was compared also with the Beckman Tg Access assay and another subset (n = 122) with Abbott Tg on the Alinity i analyzer.

Results

LoQ was verified to be less than or equal to 0.1 ng/ml confirming that the Tg assay on ARCHITECT and Alinity is highly sensitive. Correlation of ARCHITECT, Alinity, and Roche was excellent with a slope between 0.9 and 1.1 and a correlation coefficient >0.98. Correlation to Beckmann Tg was also very good, but the differences in absolute values were significant (slope: 1.477).

Conclusions

The Abbott Thyroglobulin assay, which is standardized to CRM‐457, demonstrated a high correlation to the Roche and Beckman Tg assays, though good agreement of absolute values was only observed between Abbott and Roche. Strength of correlation and slope were not affected by the presence of anti‐Tg indicating that all assays included in the study have a similar susceptibility to anti‐Tg.

The utility of serum anti-thyroglobulin antibody and thyroglobulin in the preoperative differential diagnosis of thyroid follicular neoplasms

PURPOSE

Distinguishing follicular thyroid carcinoma (FTC) from follicular thyroid adenoma (FTA) before surgery is inherently challenging owing to the lack of malignant features on ultrasound, poor sensitivity of fine-needle biopsy, and the absence of definitive markers. We investigated whether thyroglobulin (Tg), anti-thyroglobulin antibody (TgAb), thyroid peroxidase antibodies (TPOAb), and thyroid stimulating hormone (TSH) can help differentiate FTC from FTA.

METHODS

Data pertaining to 319 patients with follicular neoplasms were retrospectively analyzed. We compared the serum markers between patients with confirmed FTC and FTA. We also analyzed the prevalence of FTC in different subgroups of patients based on serum marker levels.

RESULTS

TgAb was a risk factor for FTC. Compared to TgAb ≤11.68 IU/mL group, the odds ratio (OR) for FTC in TgAb 11.69-30.50 IU/mL group and TgAb >30.50 IU/mL group were 2.206 (1.114-4.369, P = 0.023) and 3.247 (1.684-6.260, P < 0.001), respectively. The prevalence of malignancy in TgAb >30.50 IU/mL group was significantly higher than in the TgAb ≤11.68 IU/mL group (32.9 vs. 13.1%, P = 0.001). In patients with TgAb (-) status, Tg was another risk factor for FTC. Compared to Tg ≤38.51 ng/mL group, OR of Tg >434.60 ng/mL group was 3.836 (1.625-9.058, P = 0.002); the prevalence of malignancy in the Tg >434.60 ng/mL group was 47.2% and higher than other groups.

CONCLUSIONS

TgAb and Tg levels may be useful markers for preoperative differential diagnosis of follicular neoplasms. Higher TgAb and Tg levels were associated with greater malignant risk. Thus, we should be cautious of preoperative TgAb and Tg in follicular neoplasms.

Serum thyroglobulin is associated with orbitopathy in Graves' disease

PURPOSE

Serum thyroglobulin levels are often elevated in Graves' disease (GD) and in most cases decrease during treatment. Its relation to Graves' orbitopathy (GO) has not been clarified. Previously, a risk of GO has been linked to smoking, TSH receptor stimulation, high TSH-receptor antibodies (TRAb), low thyroid peroxidase and thyroglobulin antibodies (TPOAb, TgAb).

METHODS

We examined Tg levels in 30 consecutive patients with GD were given drug therapy (methimazole + thyroxine) for up to 24 months. GO was identified by clinical signs and symptoms. 17 patients had GO, 11 of whom had it at diagnosis while 6 developed GO during treatment. During the study, 5 subjects were referred to radioiodine treatment, 3 to surgery. The remaining 22 subjects (GO n = 12, non-GO n = 10) completed the drug regimen.

RESULTS

At diagnosis, Tg levels in GO patients (n = 11) were higher (84, 30-555 µg/L, median, range) than in non-GO patients (n = 19) (38, 3.5-287 µg/L), p = 0.042. Adding the 6 subjects who developed eye symptoms during treatment to the GO group (n = 17), yielded p = 0.001 vs. non-GO (n = 13). TRAb tended to be higher, while TPOAb and TgAb tended to be lower in the GO group. For the 22 patients who completed the drug regimen, Tg levels were higher in GO (n = 12) vs. non-GO (n = 10), p = 0.004, whereas TRAb levels did not differ.

CONCLUSION

The data may suggest that evaluation of thyroglobulin levels in GD could contribute to identify patients at increased risk of developing GO. Possibly, thyroidal release of Tg in GD reflects a disturbance that also impacts retroorbital tissues.

Effect of Thyroglobulin Autoantibodies on the Metabolic Clearance of Serum Thyroglobulin

BACKGROUND

In order to establish whether thyroglobulin autoantibodies (TgAb) influence the metabolic clearance of thyroglobulin (Tg) in humans, serum Tg and TgAb were correlated shortly after radioiodine (¹³¹I) treatment.

METHODS

Samples were collected from 30 consecutive patients undergoing ¹³¹I activity for Graves' hyperthyroidism at the time of treatment and every 15 days thereafter, up to 90 days. Tg and TgAb were measured by immunometric assays (functional sensitivities: 0.1 ng/mL and 8 IU/mL).

RESULTS

Tg was detectable in all patients at day 0. Tg concentrations rose from a mean of 33.2 ng/mL [confidence interval (CI) 17.8-61.0 ng/mL] at day 0 to a mean of 214.6 ng/mL [CI 116.9-393.4 ng/mL] at day 30 and then steadily decreased, reaching the lowest concentration at day 90 (M = 10.9 ng/mL [CI 5.5-20.9 ng/mL]). Compared to their levels at day 0 (M = 23.6 IU/mL [CI 10.5-52.9 IU/mL]), TgAb remained stable through day 15 and then gradually increased up to a mean of 116.6 IU/mL [CI 51.9-262.2 IU/mL] at day 90. Patients were then split into two groups according to their TgAb status at day 0: undetectable (<8 IU/mL; 9 patients) or detectable (≥8 IU/mL; 21 patients) TgAb. Compared to the other cohort, patients with detectable TgAb showed significantly lower Tg concentrations at day 0 (M = 20.3 ng/mL [CI 10.1-40.2 ng/mL] vs. M = 101.8 ng/mL [CI 36.6-279.8 ng/mL]), similar at day 15, lower levels at day 30 (M = 146.5 ng/mL [CI 74.3-287.8 ng/mL] vs. M = 514.8 ng/mL [CI 187.8-1407.9 ng/mL]), at day 45 (M = 87.5 ng/mL [CI 43.1-176.6 ng/mL] vs. M = 337.9 ng/mL [CI 120.1-947.0 ng/mL]), at day 60 (M = 61.6 ng/mL [CI 31.0-121.4 ng/mL] vs. M = 255.8 ng/mL [CI 79.0-823.8 ng/mL]), and at day 75 (M = 24.5 ng/mL [CI 11.9-49.2 ng/mL] vs. M = 249.5 ng/mL [CI 63.5-971.1 ng/mL]), and similar levels at day 90. Patients with detectable TgAb showed a lower (M = 182.5 ng/mL [CI 92.0-361.0 ng/mL] vs. M = 514.8 ng/mL [CI 187.8-1407.9 ng/mL]) and an earlier (day 15 vs. day 30) peak of Tg. The mean Tg concentration was lower in patients with detectable TgAb than in those with undetectable TgAb (area under the curve: 17,340 ± 16,481 ng/mL vs. 36,883 ± 44,625 ng/mL; p = 0.02).

CONCLUSIONS

TgAb influence the changes in Tg concentrations observed immediately after ¹³¹I treatment, inducing lower levels and an earlier peak of Tg. These observations indicate that TgAb significantly influence the metabolic clearance of Tg, supporting the concept that their interference in the measurement of Tg is mainly due to an in vivo effect.

Implications of thyroglobulin antibody positivity in patients with differentiated thyroid cancer: a clinical position statement

BACKGROUND

Even though the presence of antithyroglobulin antibodies (TgAbs) represents a significant problem in the follow-up of patients with differentiated thyroid cancer (DTC), the current guidelines on the management of DTC that have been published in recent years contain no text concerning the methods to be used for detecting such antibody-related interference in thyroglobulin (Tg) measurement or how to manage TgAb-positive patients in whom Tg cannot be used reliably as a tumor marker.

AIM

An international group of experts from the European Thyroid Association Cancer Research Network who are involved in the care of DTC patients met twice to form a consensus opinion on how to proceed with treatment and follow-up in TgAb-positive DTC patients based on the available evidence in the literature. Here we will report on the consensus opinions that were reached regarding technical and clinical issues.

RESULTS

This clinical opinion article provides an overview of the available evidence and the resulting consensus recommendations. The current literature does not provide sufficient data for giving evidence-based answers to many questions arising in the care of TgAb-positive DTC patients. Where insufficient evidence was available, a thorough discussion by a group of physician-scientists, all of whom have a distinguished track record in thyroid cancer care, was held to arrive at a consensus expert opinion. The questions and answers discussed were then summarized into an algorithm for the management of TgAb-positive patients.

CONCLUSION

We were able to define 26 consensus expert recommendations and a resulting algorithm for the care of TgAb-positive DTC patients.

Thyroid hyperactivity with high thyroglobulin in serum despite sufficient iodine intake in chronic cold adaptation in an Arctic Inuit hunter population

OBJECTIVE

Adult man hosts brown adipose tissue with the capacity to consume energy and dissipate heat. This is essential for non-shivering thermogenesis and its activation depends on sympathetic activity and thyroid hormones. This led us to evaluate the impact of chronic cold exposure on thyroid activity and thyroid hormones in serum in Arctic residents.

DESIGN

Comparative, population-based study (n = 535) performed in Greenland.

METHODS

Hunters were compared with other men, and Inuit in remote settlements in East Greenland with no modern housing facilities were compared with the residents of the capital city in West Greenland and residents of a major town in East Greenland in a cross-sectional study. We used interview-based questionnaires, measured TSH, free thyroxine, free triiodothyronine (fT(3)), thyroglobulin (TG) antibody and TG (a measure of thyroid activity) in serum, and iodine and creatinine in spot urine samples.

RESULTS

Serum TG was the highest among hunters (P = 0.009) and settlement dwellers (P = 0.001), who were most markedly exposed to cold, even though they had the highest urinary iodine excretion (hunters, P < 0.001; settlement dwellers, P < 0.001). Hunters and settlement dwellers also had the lowest fT(3) (hunters, P < 0.001; settlement dwellers, P < 0.001) after adjusting for gender, age, smoking habits, alcohol intake and iodine excretion in multivariate linear regression models. TSH was not influenced by measures of cold exposure (hunter, P = 0.36; residence, P = 0.91).

CONCLUSIONS

Cold exposure influenced thyroid hormones and TG in serum in Arctic populations consistent with consumption of thyroid hormone and higher thyroid hormone turnover. Findings emphasise that changes in thyroid activity are essential in cold adaptation in Arctic residents.

Measuring thyroglobulin and thyroglobulin autoantibody in patients with differentiated thyroid cancer

Measurement of serum thyroglobulin is primarily used as a tumor marker in the postoperative management of patients with differentiated thyroid cancer. Unfortunately, the technical quality of current thyroglobulin assay methods varies and influences the clinical utility of this test. Two different methodologic approaches are used to measure serum thyroglobulin: the original competitive radioimmunoassay methodology and noncompetitive immunometric assay methods. Although the newer immunometric assays offer the technical benefits of eliminating the use of isotopes, using smaller specimen volumes, and having higher sensitivity potential, shorter turnaround times and the convenience of automation, immunometric assays also have a higher propensity for interference from both thyroglobulin autoantibodies and heterophilic antibodies, if present in the specimen. It is critical that physicians understand the technical limitations inherent in thyroglobulin measurement in order to effectively use this test for the postoperative management of patients with differentiated thyroid cancers.

Importance of the Detection Method for Thyroglobulin Antibodies for the Validity of Thyroglobulin Measurements in Sera from Patients with Graves Disease

Background: The use of recovery tests has been proposed to disclose interferences from anti-thyroglobulin antibodies (TgAbs) in thyroglobulin (Tg) assays. We studied the value of a recovery test in Tg measurement by a new commercial IRMA.

Methods: Blood samples were collected from 153 patients with untreated Graves disease. Tg and TgAbs were measured by IRMA and RIA, respectively (Dynotest Tg-plus and Dynotest anti-Tgn; Brahms Diagnostica). The recoveries of added amounts of Tg were calculated for each serum.

Results: TgAbs were detected in 72 of the 153 patients (47%). The recovery test results for the 81 TgAb-negative sera (median, 101%; range, 80–115%) were identical to the results for the 91 controls (median, 102%; range, 80–124%). By contrast, significantly lower recovery test results were observed for the 72 TgAb-positive sera (median, 79%; range, 60–103%; Z = −8.363; P &lt;0.0001). In the 34 of the 72 TgAb-positive sera with a normal recovery test, Tg concentrations were significantly lower (median Tg, 13.6 μg/L; range, 1.1–360 μg/L) than those measured in the TgAb-negative sera (median, 107 μg/L; range, 1.2–700 μg/L; Z = −3.797; P &lt;0.0001).

Conclusions: Tg values were decreased in TgAb-positive sera even when the results of the recovery tests were normal. This test should not be used alone to determine the validity of a serum Tg measurement in Graves disease.

Variability of serum thyroglobulin levels is determined by a major gene

OBJECTIVE

There are large variations in the circulating concentrations of thyroglobulin. The purpose of this study was to explore the possibility of a genetic basis for the variability of serum concentration of thyroglobulin (Tg) in euthyroid individuals.

DESIGN

The serum concentration of thyroglobulin (Tg) varies several-fold in euthyroid individuals. Other circulating proteins also show wide normal ranges of concentration and these variations have been shown to have a genetic as well as an environmental basis. To explore the possibility of a genetic basis for variability in serum Tg levels, an analysis was made of serum Tg levels in 44 pairs of identical twins and 66 nuclear families who were euthyroid and thyroid autoantibody negative (thereby eliminating subclinical autoimmune thyroid disease and Tg autoantibody interference with the Tg assay).

RESULTS

Each pair of identical twins tended to have a similar Tg level and the overall correlation was highly significant (r = 0.734, P < 0.001). There was no relation between Tg and TSH levels in the twins (r = 0.119; P = 0.366). Segregation analysis of the 66 families showed that where both parents had Tg levels above the overall median for the subjects (males, 19 micrograms/l; females, 33 micrograms/l), 73% of the offspring also had concentrations above these levels, compared with 30% of the offspring when one parent had a high Tg level and only 16% in families where neither parent had a high Tg level.

CONCLUSIONS

Complex segregation analysis using the computer program Pointer suggested that variability in Tg levels was the result of a major dominant-like gene effect (accounting for 80% of the variability) combined with a multifactorial component. Thyroglobulin, a template for thyroid hormone production, is also a major thyroid autoantigen and inherited variations in serum Tg levels may have implications for the pathogenesis of autoimmune thyroid disease.

Occurrence of ophthalmopathy after treatment for Graves' hyperthyroidism. The Thyroid Study Group

BACKGROUND

Ophthalmopathy caused by Graves' disease may first appear or worsen during or after treatment for hyperthyroidism. It is not known, however, whether choosing to treat hyperthyroidism with antithyroid drugs, iodine-131, or surgery affects the development or aggravation of Graves' ophthalmopathy.

METHODS

We studied 168 patients with hyperthyroidism caused by Graves' disease, stratified into two age groups--20 to 34 years (54 patients, group 1) and 35 to 55 years (114 patients, group 2). The patients in group 1 were randomly assigned to treatment with methimazole for 18 months or subtotal thyroidectomy, and those in group 2 to either of these two treatments or to iodine-131 therapy. All the patients received thyroxine to avert hypothyroidism, except those treated with iodine-131, who received thyroxine only if hypothyroidism developed. The duration of follow-up was at least 24 months.

RESULTS

Twenty-two patients (13 percent) had infiltrative Graves' ophthalmopathy at randomization. During follow-up, ophthalmopathy developed for the first time in 22 patients (13 percent) and worsened in 8 patients (5 percent). The frequency of the development or worsening of ophthalmopathy was similar among the patients in group 1 (medical therapy, 4 of 27 patients [15 percent]; and surgery, 3 of 27 patients [11 percent]). In group 2, ophthalmopathy developed or worsened in 4 of the 38 patients (10 percent) treated medically, 6 of the 37 patients (16 percent) treated surgically, and 13 of the 39 patients (33 percent) given iodine-131 (P = 0.02 for the comparison between the iodine-131 subgroup and the others combined). The risk of the development or worsening of ophthalmopathy increased as pretreatment serum triiodothyronine concentrations increased.

CONCLUSIONS

As compared with other forms of antithyroid therapy, iodine-131 is more likely to be followed by the development or exacerbation of Graves' ophthalmopathy.

Serum thyroid-stimulating antibody, thyroglobulin levels, and thyroid suppressibility measurement as predictors of the outcome of combined methimazole and triiodothyronine therapy in Graves' disease

The value of the criteria used to anticipate the outcome of treatment of Graves' hyperthyroid patients with methimazole (MMI) remains controversial. We have reported that high MMI doses combined with T3 administration was correlated with higher remission rates. In this study, we used the lowest MMI dose able to control the hyperthyroidism, keeping the free T4 index (FT4I) values below the normal range throughout treatment, and compared the results with patients treated with a high MMI regimen. Both groups received T3. We also evaluated the usefulness of goiter size, serum thyroid-stimulating antibody (TSAb: adenylate cyclase stimulation in human thyroid membrane), thyroglobulin (Tg) levels, and the T3 suppressibility of 24 h RAIU as prognostic markers for the outcome of Graves' disease therapy. Twenty-four Graves' hyperthyroid patients were treated with high MMI dose (mean +/- SD 60 +/- 19, range 40-120 mg daily), and 25 patients received low MMI dose (17 +/- 4.3, 5-20 mg daily). T3, 75 micrograms daily, was given to both groups of patients for 15 +/- 4 (13-22) months of treatment. After cessation of drug therapy, 31 patients (63%) remained euthyroid for 18 +/- 3 (13-49) months of follow-up, 15 (62.5%) and 16 (64%) patients in the high and low dose groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum thyroglobulin concentration as an indicator for assessing thyroid stimulation in patients with Graves' disease during antithyroid drug therapy

PURPOSE

The purpose of this study was to elucidate the mechanism of regulation of serum thyroglobulin concentration in patients with Graves' disease and to establish the clinical usefulness of this measurement.

PATIENTS AND METHODS

Serum thyroglobulin concentration was analyzed in relation to serum thyrotropin receptor antibody (TRab) titer and thyrotropin concentration in 166 patients with Graves' disease without thyroglobulin antibody.

RESULTS

A total of 113 patients were treated and had been kept euthyroid for at least 10 months with methimazole and underwent a triiodothyronine (T3) suppression test. At the time of the T3 suppression test, the serum thyroglobulin concentration (ng/mL) was 33 +/- 31 in 80 of them with T3-suppressible (radioiodine uptake less than 12%) thyroids, negative TRab titers (less than 15% displacement), and normal serum thyrotropin concentrations (0.1 to 3.0 mU/L). Patients with T3-non-suppressible thyroids were divided into three subgroups according to serum TRab titers and thyrotropin concentrations: those with a negative TRab titer and a normal serum thyrotropin concentration (n = 9), those with a positive TRab titer and a normal thyrotropin concentration (n = 18), and those with a positive TRab titer and undetectable thyrotropin (n = 6). Serum thyroglobulin concentrations (ng/mL) were 116 +/- 40 in the first group, 249 +/- 194 in the second group, and 399 +/- 205 in the third group. In the other 39 methimazole-treated patients, 72 determinations of serum thyroglobulin concentration were performed either before or during treatment without the T3 suppression test, and it correlated well with the TRab titer but not with the serum thyrotropin concentration. In 14 patients who became hypothyroid due to excess methimazole, the serum thyroglobulin concentration increased concurrently with elevation of the serum thyrotropin concentration and normalized during thyroxine supplementation. In treated patients with T3-suppressible thyroids, the serum thyroglobulin concentration was similar among those with positive (n = 54) and negative (n = 26) microsomal antibody, indicating that the presence of Hashimoto's thyroiditis does not profoundly affect the serum thyroglobulin level. Among 80 patients with T3-suppressible thyroids who were followed without methimazole for a mean period of 31.1 months, eight (10%) experienced a clinically overt recurrence of hyperthyroidism. Serum thyroglobulin concentration and TRab titer (%) in these eight patients were 188.1 +/- 101.7 and 27.8 +/- 12.6, respectively. Thyroglobulin and TRab did not increase in the patients who remained euthyroid (n = 71) or who experienced subclinical recurrence (n = 1).

CONCLUSIONS

Abnormal thyroid stimulator(s) and thyrotropin synergistically (if both are present in the serum) or independently (if either one is present) stimulate thyroglobulin secretion in patients with Graves' disease. Therefore, serum thyroglobulin concentration can be a useful means of assessing the degree of thyroidal stimulation and, if serum thyrotropin is normal or suppressed, correlates well with thyroidal stimulation even in patients with a negative TRab titer.

Thyroid iodine content and serum thyroglobulin level following external irradiation to the neck for Hodgkin's disease

Fifty-four clinically euthyroid patients were evaluated 1 up to 17 yr after external irradiation to the neck for Hodgkin's disease. T4 level was decreased in 6%, while basal TSH level was increased in 44%, and TSH response to TRH was increased in 66% of the patients with normal basal TSH level. Thyroid iodine content (TIC), measured in 50 patients, was below 5 mg in 18. The 29 patients with normal basal TSH level had a mean TIC (6.8 +/- 2.7 mg) significantly lower (p less than 0.01) than the control population (14.6 +/- 5 mg). A significant positive correlation was found between log T4 and log TIC (r = 0.55, p less than 0.01). Thyroglobulin (Tg) level was increased in 53% of the patients with no palpable thyroid abnormality. It was not related to TSH level but was related to younger age at irradiation. T4 treatment decreased Tg level to the normal range in 5 of 8 patients. These facts suggest subclinical thyroid abnormalities and patients with elevated Tg levels should be considered at risk for developing a thyroid tumor.

Graves' disease in pregnancy: TSH receptor binding inhibiting immunoglobulins and maternal and neonatal thyroid function

We studied interrelationships between maternal and neonatal thyroid function, TSH receptor binding inhibiting immunoglobulins (TBII), and dose of thionamide antithyroid drugs in 44 women with active Graves' disease presenting during 46 pregnancies, and their 48 infants. The women were treated with propylthiouracil (PTU) or carbimazole (CBZ). In 30 pregnancies (30 infants) treatment was withdrawn from 3 to 18 weeks before delivery (Group A). Drug treatment (PTU, n = 10, dose 50-400 mg/day or CBZ, n = 6, dose 5-45 mg/day) was continued throughout pregnancy and delivery in 16 pregnancies producing 18 infants (Group B). The maternal TBII at delivery was well correlated with maternal free thyroxine index (FTI) averaged over the third trimester (r = 0.603, P less than 0.001) and umbilical venous serum TBII (r = 0.940, P less than 0.001). Neonatal FTI was independently related to umbilical vein TBII (t = 2.29, P = 0.03) and maternal dose of antithyroid drug (t = -2.21, P = 0.03). Neonatal thyrotoxicosis was seen in all four infants (8% of births) of women whose TBII levels at delivery exceeded 70%. No child was born with a subnormal FTI but 7/18 infants in group B had raised TSH at birth. This was more likely to occur (P = 0.05) if maternal TBII was less than 30% (6/10) than if maternal TBII was greater than 30% (1/8). Four Group B women with FTI in the lower half of the reference range delivered infants with raised TSH compared with 3/14 (21%) women whose FTI was in the upper half of the reference range or above (P = 0.05). In pregnant women with active Graves' disease TBII levels reflect stimulatory TSH receptor antibody activity. TBII measurements are of use in the prediction of neonatal thyrotoxicosis and impaired neonatal thyroid function in infants of women treated with antithyroid drugs.

Thyroglobulin, thyrotropin and thyrotropin binding inhibiting immunoglobulins assayed at the withdrawal of antithyroid drug therapy as predictors of relapse of Graves' disease within one year

"Sensitive" thyrotropin (TSH), thyroglobulin (TG) and even thyrotropin binding inhibiting immunoglobulins (TBII) assays are now widely available. The objective of the present study was to determine the most accurate of these three parameters to predict the relapse of Graves' disease during the year following treatment discontinuation and to evaluate whether the assay of three markers is able to improve the prediction. TSH, TG and TBII were measured in the sera of 67 Graves' disease patients after at least 12 months of medical treatment. In 52 patients, TBII had also been determined before the beginning of the medical treatment. Under treatment, all the patients were clinically and biologically euthyroid, but in 9 goitrous patients it was impossible to lower the doses of carbimazole without an immediate relapse. The TSH levels of these 9 patients were still low in all cases but one; TG and TBII levels were abnormal in all. In the other 58 patients, the treatment was discontinued; 22 relapsed within one year, more frequently when a goiter was present. The most reliable parameter for the prediction of relapse was found to be TBII, as its specificity was high (94.5%), although its sensitivity was poor (45%); TG was more sensitive (64%) but far less specific (57%); TSH and "initial" TBII appeared to be of a little interest. When TBII was elevated prior to the withdrawal of treatment, the determination of TG was useful: abnormal values of both TBII and TG were always associated with a relapse. When TBII testing was negative, the relapse risk fell to 0.26, and to 0.08 when three criteria were matched: no goiter, negative TBII, normal TG.

Serum thyroglobulin--its measurement and clinical use

Radioimmunoassays (RIA) have been shown to be unreliable in measuring serum thyroglobulin levels in patients with antithyroglobulin antibodies. The aim of this study was twofold. Firstly to compare the abilities of two immunoradiometric assays (IRMA), one commercially available, the other an 'in house' assay, with a conventional RIA. In addition the prognostic value of serum thyroglobulin levels in patients likely to relapse following a course of antithyroid drugs for Graves' disease was examined. The results obtained showed both of the IRMA methods to be unaffected by the presence of antithyroglobulin antibodies. Serum thyroglobulin levels were found to be poor predictors of relapse or remission following a 12 month course of antithyroid drugs.

Immunoreactive thyroglobulin in sera and saliva of patients with various thyroid disorders: role of autoantibodies

The present study was designed to assess the transfer of thyroglobulin (Tg) and anti-Tg antibodies (TgAb) to saliva in subjects with positive TgAb in their sera. Group I consisted of normal euthyroid control subjects (n = 10). Group II were patients with various thyroid disorders and no TgAb in their sera (n = 6). Group III were patients with thyroid disorders and TgAb in their sera (n = 31). The mean serum Tg level (+/- SE) and mean TgAb level [mean % binding +/- SE (range)] were as follows: Group I, Tg: 22.0 ng/ml +/- 1.64 (n = 10); TgAb 1.91% +/- 0.34 (range 0.6% to 4%). Group II, Tg: 119.8 ng/ml +/- 28.0 (n = 6) TgAb 1.59% +/- 0.34 (0.64% to 2.7%). Group III Tg 167.9 ng/ml +/- 41.0 (n = 31) TgAb 23.2% +/- 3.87 (4.2% to 67.5%). The mean salivary Tg level (SaTg) and mean TgAb binding (% +/- SE range) in saliva were as follows: Group I SaTg 2.07 ng/ml +/- 0.39 (n = 10) SaTgAb 1.13% +/- 0.38 (0% to 3.1). Group II SaTg 3.41 ng/ml +/- 0.67 (n = 6), SaTgAb 0.55% +/- 0.29 (0-1.9%). Group III SaTg 5.22 ng/ml +/- 0.96 (n = 31), SaTgAb 3.1% +/- 1.58 (0 to 47.7%). Salivary TgAb were only present in 4 out of 31 cases of Group III. Mean serum Tg in group IV-A was 75.01 ng/ml +/- 52.1 (n = 11). Mean serum TgAb in group IV-A was 1.94% +/- 0.31 (n = 11).(ABSTRACT TRUNCATED AT 250 WORDS)

Sequential changes in serum thyroglobulin, triiodothyronine, and thyroxine following partial thyroidectomy for nontoxic nodular goiter

The sequential changes in serum thyroglobulin (Tg), thyroxine (T4), free thyroxine (FT4), triiodothyronine (T3) and thyrotropin (TSH) were evaluated in ten patients on whom partial thyroidectomy for nontoxic nodular goiter had been performed. These changes were compared with those in ten patients who underwent upper abdominal surgery (cholecystectomy) under similar anesthesia, and whose calorie and fluid intake was similar until at least 48 hours after surgery. In agreement with previous reports, marked elevations in serum Tg that reached peak concentration (660 to 1350 ng/mL) at one or two hours after the thyroid incision (mean +/- SD; 787 +/- 304.0 ng/mL and 839 +/- 345.7 ng/mL, respectively) were observed. On the other hand, the significant but minimal increases in serum T4 and FT4 were observed at 24 hours (P less than .001 and P less than .001, respectively), 48 hours (P less than .01 and P less than .001, respectively), and 72 hours (P less than .01 and P less than .01, respectively) after the thyroid incision compared with the level just prior to the thyroid incision. Similarly, serum T3 also increased significantly at 6 to 168 hours after the thyroid incision (P less than .01, P less than .05, P less than .05, P less than .05, and P less than .05, respectively). These increases in serum T4, FT4 and T3 were not observed in the cholecystectomy patients. The mean serum TSH levels at 24 to 72 hours after thyroid incision and those at 6 to 48 hours after the abdominal incision were significantly decreased compared with those before thyroid and abdominal incision, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of prednisolone and salicylate on serum thyroglobulin level in patients with subacute thyroiditis

Twelve patients with subacute thyroiditis were divided into two groups and treated with prednisolone or salicylate. The initially elevated T4, T3, free T4 (FT4), free T3 (FT3) and erythrocyte sedimentation rate (ESR) were reduced during the early phase within about 4 weeks in both groups. The serum levels of thyroglobulin (Tg) were elevated in both groups treated with salicylate and prednisolone (252 +/- SD 117 ng/ml and 233 +/- SD 157 ng/ml, respectively) at initial examination. The serum level of Tg declined during the early phase with prednisolone treatment, and it reached normal values at the end of the early phase (17 +/- SD 15 ng/ml). With salicylate treatment, the decline of levels of Tg was delayed and it was elevated (80 +/- SD 34 ng/ml) despite normal levels of thyroid hormones and ESR at the end of early phase. The serum level of Tg at the end of the early phase of prednisolone treated was significantly lower than that of salicylate treatment (P less than 0.01). It is suggested that the effect of prednisolone on rapid decrease of Tg may be related to its inhibitory action of intrathyroid hydrolysis.

Effect of therapy on the serum thyroglobulin concentration in patients with toxic diffuse goiter, toxic nodular goiter and toxic adenoma

Serum thyroglobulin (S-Tg) was measured in 104 patients with thyrotoxicosis, 59 of whom had toxic diffuse goiter (Graves' disease), in 30 with toxic nodular goiter and in 15 with toxic adenoma. Before treatment, most patients had increased S-Tg concentrations, regardless of what type of thyrotoxicosis they had. After therapy the course of the S-Tg varied, two major patterns being observed: the S-Tg concentration increased in some patients but decreased in others, although no relationship could be found between these patterns and the outcome of therapy, the presence or absence of thyroglobulin antibodies (Tg-ab) or changes in the Tg-ab titer. However, the median pretreatment concentrations of S-Tg were significantly higher in patients with toxic nodular goiter and toxic adenoma than in those with toxic diffuse goiter (p less than 0.001 and p less than 0.05, respectively), but did not differ significantly between patients with toxic nodular goiter and toxic adenoma. The lowest posttreatment S-Tg concentrations were found after surgery, irrespective of type of thyrotoxicosis. The median pretreatment and posttreatment S-Tg concentrations in patients with toxic diffuse goiter who relapsed, did not differ from those patients in remission. This was also true of patients with toxic nodular goiter. In both groups, however, there was a tendency towards higher pretreatment S-Tg values in patients who subsequently relapsed. Serial determinations of S-Tg, on the other hand, are of limited value in predicting the risk of recurrence, independent of which type of thyrotoxicosis is involved.

TSH receptor antibody induction of thyroglobulin release from human thyroid cell monolayers

We investigated the influence of TSH receptor antibody (TRA), as detected by inhibition of 125I-bTSH binding to detergent solubilized porcine TSH receptors, on in-vitro thyroglobulin (hTg) production using normal thyroid cells in monolayer. Secretion of hTg into the culture medium was analysed by a non-competitive enzyme immunosorbent (ELISA) technique utilizing two murine monoclonal antibodies. Basal hTg release (mean +/- SD 124 +/- 27 ng/10(5) cells/6 d, n = 5) was stimulated by bTSH (10, 10(2), 10(3) microU/ml) in a dose related manner (mean +/- SD 191 +/- 24, 587 +/- 80, 695 +/- 66 ng/10(5) cells/6 d, respectively). IgG (2 mg/ml) from seven patients with hyperthyroid Graves' disease, and known titres of TRA, similarly enhanced production of hTg, in a dose and time-dependent manner, when compared to control IgG. The degree of induction varied from a 140-230% increase in total hTg release over a 6-day incubation period. There was a direct correlation between the degree of 125I-bTSH binding inhibitory activity and the hTg response (r = 0.9, P less than 0.01). These data demonstrate that TSH receptor antibodies enhance hTg release from human thyroid cell monolayers and allow an assessment to be made of antibody-activated post receptor mechanisms.

Plasmapheresis: an adjunct to medical management of severe hyperthyroidism

A woman with hyperthyroidism and myasthenia gravis developed respiratory failure in association with radiation-induced thyroiditis. Treatment with steroids, propylthiouracil, propranolol, iodine, and plasmapheresis was associated with dramatic reduction in serum triiodothyronine (T3), serum thyroxine (T4), and thyroglobulin levels and prompt recovery of the patient. The medications that this patient received have been shown to cause an abrupt decline in serum T3 levels with little or no effect on the serum T4 concentration. The 56% decline in serum T4 observed in this patient during the first 24 hours of therapy suggests that plasmapheresis may be a useful adjunct to medical therapy in selected patients with severe hyperthyroidism.

Correlation of thyroglobulin measurements and radioiodine scans in the follow-up of patients with differentiated thyroid cancer

Correlation of radioiodine (131I) scans and serum thyroglobulin (Tg) concentrations were performed in the follow-up of 85 differentiated thyroid cancer patients who had undergone total thyroidectomy. Tg results were also compared with the control group of 33 thyroidectomized patients with no evidence of thyroid carcinoma and normal values for Tg established. Excellent correlation between Tg and scans was noted in patients with scan evidence of metastasis distant from the neck. Poor correlation was present in patients with scan evidence of local neck metastasis only, thyroid bed activity, and those with mediastinal activity. In addition, in 8% of the patients, the Tg assay could not be performed because of interfering antibodies. The conclusion is that elevated Tg concentration is a good indicator of metastasis outside of the neck as detected by 131I scans. Caution should be used when Tg alone is used in evaluating local neck metastasis demonstrated on scans. The significance of mediastinal activity warrants further investigation.

Serum thyroglobulin in patients with autonomous thyroid nodules

To investigate further the relationship between thyroid hormones and thyroglobulin (TG) secretion, total and free thyroid hormone levels, TSH and its response to TRH and serum TG concentrations were determined in 61 patients with solitary autonomous thyroid nodules. Thyroid function varied widely from euthyroidism to clearcut thyrotoxicosis. Serum TG levels were significantly higher in patients than in normal controls. Individually they were above the normal range (greater than 50 ng/ml) in 95% of the patients, as well as in those with normal total and/or free thyroid hormone levels. Patients with high total and/or free thyroid hormone levels had higher TG concentrations than euthyroid patients. TG concentrations were significantly correlated with FT3 values. They were higher in patients in whom TSH was unresponsive to TRH than in the responsive groups. TG was also slightly higher in patients with hot nodules than in those with warm nodules. These data seem to indicate that TG is secreted along with thyroid hormones in the absence of any stimulatory action. It also is a sensitive index of thyroid hyperfunction. Twenty patients were controlled 6 months after nodulectomy. TG levels, though significantly lower than in the preoperative state, were still higher than in normal subjects. This increase was attributed to persistent hyperthyroidism in two patients only. The observation that the increase in TSH after TRH stimulation in post-operative patients was greater than that found in normal controls led us to believe that in most cases the high TG levels after surgery are due to stimulation of the normal thyroid tissue by rebound TSH secretion.

Serum thyroglobulin in newborns' cord blood, in childhood and adolescence: a physiological indicator of thyroidal status

Serum thyroglobulin (Tg) was measured in the cord blood of 635 newborns and serum thyroxine (T4) reverse triiodothyronine (rT3), TSH and T3 were measured in about 200 of them. Cord Tg was detectable in all newborns with a mean +/- SE value (50 +/- 1.3 ng/ml) higher than that found in the serum of adult subjects (n = 144; Tg = 13 +/- 1.1; p less than 0.0001). Cord Tg had a log-normal distribution. A low, but positive correlation was found between cord Tg and cord TSH (n = 242; r = 0.17; p less than 0.05) but not with cord T4 or cord rT3. Gestational age was negatively correlated with cord Tg or cord rT3 (rS = 0.97; p less than 0.01; rS = -0.89; p less than 0.02, respectively) while was positively correlated with cord T4 or cord TSH (rS = 0.85; p less than 0.05; rS = 0.86; p less than 0.01, respectively). Birth weight, maternal diabetes, induction of labor with oxitocin, cesarian section and newborns' illness showed no influence on cord Tg levels when considered alone, but decreased cord Tg levels were found in ill newborns delivered by cesarian section. On the contrary, increased cord Tg levels were present in cord blood of newborns who developed hypoglycemia soon after birth and in small for gestational age newborns. In 24 newborns studied daily for the first 6 days of life, serum Tg was always detectable with mean values not different from those found in the cord blood.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis of thyroglobulin in thyroid carcinoma patients after radioiodine therapy

Endogenously radioiodinated thyroglobulin (Tg) and the serum concentration of Tg have been measured in patients with metastatic thyroid carcinoma after therapeutic doses of radioiodine. Serial samples of blood were analyzed for both these parameters over a period of 10 to 22 days. The specific activity of Tg (cpm/ng) was calculated for each sample. Among the six patients studied, three showed constant specific activity. The specific activity of the other three fell, indicating the entering of newly synthesized Tg into the circulation. The respective amounts of Tg entering into the circulation in these three patients were 120, 852, and 20,935 ng/ml serum/day.

Long-term follow-up using serial serum thyroglobulin determinations in patients with differentiated thyroid carcinoma

Although thyroglobulin is generally recognized as a useful marker for metastases in cases of differentiated thyroid carcinoma, there have been few reports of the use of thyroglobulin determination for long-term follow-up. This report presents the results of long-term follow-up studies carried out for periods of up to 4 years in 18 patients, including 4 patients with local and 14 with distant metastases. After successful treatment, thyroglobulin fell to unmeasurable levels in the four patients with local metastases and in four of six patients with distant metastases. In some patients treated successfully with 131I, the thyroglobulin level remained elevated for several months before falling to within the normal range. Thyroglobulin levels correlated with tumor growth in six of eight patients with tumor progression, remained high with a slight downward trend in one patient, and declined to unmeasurable levels in another case. Only one patient in this group showed radioiodine uptake in the metastases at the end of the observation period. The lack of 131I uptake in the other patients probably reflects the low degree of differentiation of the metastases. The following conclusions regarding the use of thyroglobulin measurement for the long-term follow-up of thyroid carcinoma can be made: (1) Following 131I therapy for metastatic thyroid carcinoma, return of thyroglobulin levels to within the normal range may take several months. The trend observed in serial thyroglobulin determinations is more meaningful than the absolute values for evaluating the success of therapy. (2) Thyroglobulin levels correlate with tumor growth in most cases of tumor progression, even when changes in differentiation may have led to a loss of radioiodine uptake by the metastases. It may be concluded that serial thyroglobulin determinations are therefore useful for the detection of metastases that do not accumulate radioiodine.

Serum thyroglobulin in acute and chronic liver disease

In view of the widespread use of serum thyroglobulin determination in the follow-up of patients with differentiated thyroid carcinoma, the influence of acute and chronic liver disease on serum thyroglobulin concentration was investigated in thirty-seven consecutive patients with histologically proven alcoholic liver cirrhosis and twenty-three patients with acute non-alcoholic hepatitis. Seventy-four healthy volunteers served as controls. Serum thyroglobulin concentration was significantly elevated in cirrhosis: median 29.5 micrograms/l, (range 4.3-94.0 micrograms/l) compared to controls: median 16.0 micrograms/l, (range 4.8-89.6 micrograms/l), (P less than 0.001). Serum thyroglobulin concentration in patients with acute hepatitis: median 16.2 micrograms/l, (range 7.9-70.0 micrograms/l) was not significantly different from controls. The level of free-T3-index was significantly reduced and the level of free-T4-index was significantly elevated in both cirrhosis and hepatitis compared to controls. Serum TSH concentration was significantly elevated in cirrhosis compared to hepatitis and controls. Serum thyroglobulin levels were positively correlated to levels of free-T3-index (r = 0.35, P less than 0.05) and T3/T4-ratio (r = 0.40, P less than 0.05) but not to levels of serum TSH or free-T4-index or any of the liver function tests in any of the groups. In conclusion, our results do not clearly indicate whether the elevated serum thyroglobulin level in cirrhosis was caused by an impaired elimination and/or an increased secretion from the thyroid gland. The increase in serum thyroglobulin concentration in chronic alcoholic liver disease was not of a magnitude likely to cause misinterpretation of results obtained during the follow-up of patients with differentiated thyroid carcinoma.

Changes of circulating thyroid autoantibody levels during and after the therapy with methimazole in patients with Graves' disease

The changes occurring in the levels of circulating thyroid microsomal antibody (M-Ab) and antithyroglobulin antibody (Tg-Ab) during antithyroid drug therapy were studied in 32 patients receiving methimazole for Graves' disease. M-Ab was determined by competitive binding radioassay and Tg-Ab by a sandwich radiometric method. Before treatment 25 subjects (78.1%) had abnormally elevated (greater than or equal to 75 U/ml) M-Ab levels. A more than 30% reduction of M-Ab concentration with respect to the pretreatment value was found in 16 (64.0%) of these patients within the first 3-5 months of therapy, in 23 (92.0%) within 8-11 months and in 21 (84.0%) at the end of treatment (16-18 months). No change was found in the 7 patients with initial M-Ab levels less than 75 U/ml. The reduction of M-Ab was more pronounced in the patients with good control of thyrotoxicosis than in those who were still hyperthyroid or were rendered hypothyroid during treatment. Twenty-three patients were followed after completion of the course of methimazole therapy, and 13 of them showed relapse of hyperthyroidism. A significant rise of M-Ab with respect to the values observed at the end of treatment occurred in all relapsing patients who had abnormally elevated M-Ab levels before therapy. With one exception, no M-Ab increase was found in the 10 nonrelapsing patients. However, no difference between relapsing and nonrelapsing patients was observed when the M-Ab changes occurring during treatment were considered. A similar trend during and after withdrawal of therapy was noted for Tg-Ab but, because of the relatively small percentage of positive subjects (25%), the results were less conclusive. The present data indicate that methimazole treatment induces a fall of thyroid antibodies in patients with Graves' disease, and that relapse of hyperthyroidism is associated with an increase of these antibodies. However, the antibody changes occurring during treatment showed no prognostic value in predicting the outcome of therapy.

The measurement of serum thyroglobulin in the presence of thyroglobulin antibodies

In a significant proportion of patients with thyroid disorders, thyroglobulin antibodies (TgAb) invalidate double-antibody radioimmunoassays (RIA) for thyroglobulin (Tg). A modified RIA procedure for determining serum Tg in the presence of TgAb, is described. Two measurements are made on each sample. a Ratio of immunoglobulin (Ig)-bound thyroglobulin to free thyroglobulin (bound:free ratio). This is measured by the distribution of a trace quantity of 125I-Tg between bound and free fractions. b Concentration of free, i.e. unbound thyroglobulin. This is measured in the supernatant after precipitation of IgG-bound Tg. Then, bound Tg=B:F x (free Tg) and total Tg=(bound Tg)+(free Tg). Critical factors examined in the validation of the modified method were: (1) use of immunologically intact 125I-Tg (specific activity less than or equal to 5 mCi/mg); (2) equilibration of tracer Tg with endogenous serum Tg, and (3) clean separation of IgG-bound and free fractions of Tg with goat anti-human IgG. Recovery of added Tg in the presence of TgAb was 105% and interassay precision of total Tg assay was less than or equal to 9.3%. In euthyroid subjects without TgAb, the correlation between total Tg levels by the modified and standard double-antibody method was 0.931. The correlation was much poorer in the presence of TgAb (r=0.752) reflecting their interference in the standard method. Reference ranges for serum total Tg levels by the modified method in euthyroid, hyper- and hypothyroid subjects with and without TgAb are detailed.

Clinical pharmacokinetics of antithyroid drugs

Organic antithyroid drugs used today include propylthiouracil and the mercaptoimidazolines, carbimazole and methimazole. They can be measured with accuracy and in small quantities in serum by gas-liquid chromatography, high performance liquid chromatography and radio-immunoassay. Bioavailability of these drugs varies from 80 to 95%. During absorption carbimazole, which itself is inactive, is completely converted to methimazole. The total volume of distribution is about 40L for methimazole and around 30L for propylthiouracil, which is about 80% protein-bound, while methimazole is virtually non-protein-bound. Drug transfer across the placenta and into breast milk is also higher for the more lipid-soluble methimazole than for propylthiouracil, which is excreted into breast milk only in small quantities so that no harmful effect to the suckling infant is to be expected. Both drugs are concentrated in the thyroid gland, exerting an effect on intrathyroidal iodine metabolism for periods exceeding those in which serum concentrations can be measured. Less than 10% of both drugs is excreted unchanged in the urine, but detailed metabolic pathways are unknown. The half-life of methimazole is 3 to 5 hours with a total clearance of about 200ml/minute. Propylthiouracil has a half-life of 1 to 2 hours with a clearance of around 120ml/min/m2. Some studies have shown an increased rate of metabolism of anti-thyroid drugs in hyperthyroidism, in particular for methimazole. No reliable information exists regarding pharmacokinetics of these agents in renal and hepatic failure or in children. The clearance of propylthiouracil is unchanged in the elderly. Several mechanisms for the inhibiting effect of these agents on intrathyroidal hormone metabolism have been suggested. In contrast to methimazole, propylthiouracil inhibits the peripheral conversion of thyroxine to triiodothyronine. Preliminary dose-response studies with propylthiouracil suggest a peak therapeutic serum concentration of above 4 micrograms/ml in the treatment of thyrotoxicosis. The choice between the antithyroid drugs is based more upon personal preference and experience than on strict pharmacological principles, as no important differences exist between these drugs with regard to the rate of remission or frequency of occurrence of serious adverse reactions.

The comparative value of serum thyroglobulin measurements and iodine 131 total body scans in the follow-up study of patients with treated differentiated thyroid cancer

This study is an attempt to unify the evaluation of patients with well-differentiated thyroid cancer after ablative therapy. As such serum thyroglobulin determinations on and off thyroid hormone (T4) therapy and iodine 131 total body scans were examined in 53 patient studies. No metastases were found in patients whose thyroglobulin value was undetectable (less than 1 ng/ml). Values during T4 therapy that were detectable, even as low as 4.2 ng/ml, were occasionally associated with metastases. After T4 withdrawal, thyroglobulin value and scan were obtained. Neither metastasis nor clinically detectable cancer was found in patients whose thyroglobulin value was less than 10 ng/ml while off T4. Conversely, a value greater than 10 ng/ml was often associated with documented metastases even when the scan was negative. In summary, a thyroglobulin value less than 1 ng/ml during T4 therapy or less than 10 ng/ml off T4 therapy suggests successful therapy and a routine scan could be avoided unless clinically indicated. However, a value greater than 10 ng/ml suggests the presence of metastasis despite a negative scan. Thyroglobulin determination substantially improves the management of these patients.

The effect of 131I for diagnostic purposes on serum thyroglobulin (hTg) levels in subjects with thyroidal disorders

The concentration of serum thyroglobulin was measured in sera of subjects with various thyroid disorders, before and after the administration of tracer doses of 131I. The mean serum human thyroglobulin (hTg) concentration before administration of the isotope was 35.2 ng/ml +/- 7.8 (SE) in 13 subjects and 36.3 ng/ml +/- 7.9 (SE) 24 h after the administration of 131I. The data indicate that no significant release of thyroglobulin occurs 24 h after the administration of tracer doses of 131I. In 2 of the 3 subjects, however, in whom samples were obtained at 4 and 8 h after diagnostic administration of 131I, a modest rise in serum Tg levels was observed. Determinations of serum thyroglobulin levels within 24 h after the administration of a tracer dose of 131I are nevertheless valid providing one allows sufficient time to elapse for tracer decay.

The influence of subtotal thyroidectomy on the thyroglobulin binding capacity of thyrotoxic serum

It has been shown previously that large amounts of thyroglobulin are released into the circulation by the trauma of thyroid surgery. In order to characterize the response to this challenge in patients with and without autoimmune disease, serial estimations of thyroglobulin binding capacity (AgBC) using a sensitive double antibody technique were made on 105 patients undergoing partial thyroidectomy for thyrotoxicosis (70 patients prepared medically) and nontoxic goiter (35 patients). Samples were measured the day before, the day of, and on eight subsequent occasions during the first 14 days after surgery. Three distinct patterns of change in AgBC were observed in the thyrotoxic patients: i) when elevated before surgery, it fell acutely within 48 h of operation and rose again within the first 7-10 days (8 patients); ii) it rose briskly, though transiently, when low (less than 10%) before surgery (4 patients); iii) when elevated before surgery, it rose or fell gently afterwards without sudden change (7 patients). The AgBC in 51 of the Graves' disease patients never exceeded 10% during the perioperative period, and was immeasurably low in all nontoxic goiter patients. Autoimmune thyroid disease results from a disturbance of normal tolerance to thyroid antigens, and thyroid surgery provides an in vivo model in which the response to an acute antigenic challenge may be studied. Patients with Graves' disease showed varying degrees of intolerance to the challenge, while those with nontoxic goiter and no evidence of autoimmune disease were uniformly unresponsive.

Immunoradiometric assay for human thyroglobulin and variations in thyroid pathology

A specific and sensitive double antibody radioimmunoassay for measuring human serum thyroglobulin (Tg) has been developed. Serum Tg levels are reported for patients with differentiated and undifferentiated thyroid carcinomas, post-treated and untreated hyperthyroidism, thyroiditis, and cold nodular goiters. We have studied results of serum Tg levels in the follow-up and care of patients who have undergone total thyroidectomy for differentiated thyroid carcinomas. Tg has no diagnostic value in the detection of thyroid cancer, but is a reliable index of metastatic growth in the follow-up of patients with differentiated carcinomas. In addition, serum Tg determination might be helpful in the aetiological diagnosis of bone or lung metastases of unknown origin.

Serum thyroglobulin in thyroid carcinoma and other thyroid disorders

Measurements of serum thyroglobulin (hTg) were performed using a specific radioimmunoassay. Sera with detectable anti-thyroglobulin (anti-Tg) antibody titers (> or = 1:10) as assessed by passive hemagglutination were discarded. Assays were carried out under conditions in which anti-Tg titers less than 1:10 produced no interference. The assay sensitivity was 1.25 ng/ml and the mean +/- SE concentration of serum hTg in 58 control subjects was 9.5 +/- 0.9 ng/ml (range < 1.25-27 ng/ml). A slight but significant (p < 0.025) increase in the mean hTg level was observed in 12 pregnant women at delivery (25.7 +/- 5.2 ng/ml). Moderate to marked elevations of serum hTg were observed in patients with nontoxic goiter (61.4 +/- 15 ng/ml; n = 23), subacute thyroiditis (138 +/- 67 ng/ml; n = 5), toxic adenoma (129 +/- 47 ng/ml; n = 13), untreated (424 +/- 101 ng/ml; n = 35) or treated (328 +/- 222 ng/ml; n = 14) toxic diffuse goiter. 88 patients with thyroid carcinoma and 10 with nonthyroidal malignancies were studied. The mean level of serum hTg was increased in untreated differentiated thyroid carcinoma (89.5 +/- 19 ng/ml; n = 13) but not in undifferentiated (10 +/- 2.9 ng/ml; n = 6) or medullary (0.8 +/- 0.2 ng/ml; = 3) carcinoma. In treated differentiated thyroid carcinoma the mean hTg levels were normal (8.2 +/- 0.2 ng/ml) in patients (n = 24) with no evidence of either a thyroid residue or metastatic disease, moderately increased (56.6 +/- 16 ng/ml) in patients (n = 27) with residual thyroid tissue, markedly elevated in patients with lymph node metastases (199 +/- 50 ng/ml; n = 5) and extremely elevated in those with bone (4004 +/- 982 ng/ml; n = 8) or lung (2520 +/- 620 ng/ml; n = 5) metastases. There was no significant difference in serum hTg between functioning (n = 23) and nonfunctioning (n = 5) metastases as assessed by 131I whole body scan. A slight but significant (p < 0.0005) increase in the mean concentration of hTg was observed in nonthyroidal malignancies (21.7 +/- 4.5 ng/ml; n = 10). Serial measurements showed a transient increase of serum hTg after 131I therapy of differentiated thyroid carcinoma, toxic diffuse goiter or toxic adenoma, with peak values usually occurring within the first three days. A fall of serum hTg after administration of suppressive doses of thyroid hormone to patients with nontoxic goiter and a rise after discontinuation of thyroid suppressive therapy in patients with metastatic differentiated thyroid carcinoma was observed.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of irradiation on thyroid-autoantibody production

Irradiated lymphocytes have been found to stimulate thyroid-autoantibody synthesis by lymphocyte cultures. It is proposed that a similar effect is involved in the increased autoimmune response which follows radioiodine treatment for Graves' disease.