The effect of recombinant human thyrotropin (rhTSH) on thyroid function in mice and rats

The vast majority of studies to determine the biological activity of recombinant human thyrotropin (rhTSH) have been carried out in the mouse. We have recently reported that 0.1 mg of rhTSH IM (one-ninth the dose given in thyroid cancer patients) given to normal subjects elicits a brisk rise in serum thyroxine (T4), triiodothyronine (T3), and thyroglobulin (Tg) concentrations. In contrast, in initial studies in the rat, a low dose of rhTSH failed to increase serum T4 or T3 concentrations. The present study was, therefore, carried out to determine the biological activity of rhTSH in euthyroid and in T3-treated, TSH-suppressed rats and mice. Doses of rhTSH based on body weight were used and resulted in similar serum human thyrotropin (hTSH) concentrations in the two species. Euthyroid and TSH-suppressed mice responded briskly to rhTSH administration. In contrast, serum T4 did not increase after rhTSH administration in euthyroid rats. In TSH-suppressed rats, the increase in serum T4 was similar to that observed in TSH suppressed mice. These observations suggest that rhTSH more readily displaces endogenous TSH from the mouse than from the rat thyroid TSH receptor, because equal responses were observed when endogenous TSH was suppressed.

Dehydroepiandrosterone sulfate does not prevent spontaneous and iodine-induced lymphocytic thyroiditis and diabetes mellitus in the BB/Wor rat

Chronic feeding of dehydroepiandrosterone (DHEA) and its sulfated metabolite, dehydroepiandrosterone sulfate (DHEAS), has previously been reported to decrease hyperglycemia, obesity, cancer, and autoantibody generation in a number of animal models and to increase muscle mass and physiological and psychological well-being in elderly humans, although these latter studies remain controversial. The present study was carried out to determine whether large amounts of DHEAS given orally would prevent the occurrence of spontaneous and iodine-induced autoimmune lymphocytic thyroiditis (LT) and/or spontaneous insulin-dependent diabetes mellitus (DM) in male and female BB/Wor rats. DHEAS was administered by gavage (44 mg/rat/day) or in the chow (133 mg/rat/day) to LT- and DM-prone rats from 30 to 120 days of life; some of these rats also received iodine in the drinking water to enhance the incidence and intensity of LT. Onset of DM requiring protamine zinc insulin and its maintenance dose were assessed. Rats were killed at 90 or 120 days of age and blood, thyroid, adrenals, pancreases, testes, and ovaries were removed. Serum glucose, DHEA, DHEAS, thyroxine (T4), tri-iodothyronine (T3) and thyrotropin (TSH) concentrations were measured in all rats in both experiments. Serum DHEAS concentrations were 10-fold higher in the rats given the steroid by gavage or in the diet compared with levels in control rats. DHEAS administered over a prolonged period of time had no significant effect on body weight, incidence and severity of DM, incidence and intensity of spontaneous and iodine-induced LT, and thyroid, pancreas and testes weights but did significantly decrease adrenal and ovarian weights. Serum T4, T3, and TSH concentrations were similar in control and DHEAS-treated rats. In conclusion, DHEAS did not prevent the occurrence of iodine-induced or spontaneous autoimmune LT or spontaneous DM in the BB/Wor rat, at variance with its reported immunosuppressive effects in other animal models.

Successful treatment of massive acute thyroid hormone poisoning with iopanoic acid

We report a toddler with massive thyroid hormone poisoning in whom the addition of iopanoic acid to the treatment regimen (propylthiouracil and propranolol) resulted in a dramatic clinical and biochemical improvement. Iopanoic acid is a safe and effective drug in the treatment of massive thyroid hormone poisoning in children.

The effect of nicotine on thyroid function in rats

Very recently, it has been reported that subclinical hypothyroidism is more severe and peripheral markers of hypothyroidism are more pronounced in women with subclinical or overt hypothyroidism who smoke. Increased concentrations of the known goitrogen thiocyanate, generated from cigarette smoke, have been the major explanation for the decreased thyroid function in these women but do not explain the reported increased peripheral markers of hypothyroidism. There are no data on the effect of the other major product of cigarettes, nicotine, on thyroid function in vivo. The present studies were therefore performed to determine the effects of large doses of nicotine infused for 7 days on thyroid function, outer-ring 5'deiodinase activity (5'D-I), and hepatic malic enzyme activity (a measure of thyroid hormone action) in euthyroid, subclinically hypothyroid (hemithyroidectomized), and L-thyroxine (L-T4)-treated thyroidectomized rats. Nicotine infusion had no effect on serum T4, triiodothyronine (T3), thyrotropin (TSH), and cholesterol concentrations, intrathyroidal metabolism of 125I, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in euthyroid and subclinically hypothyroid rats. Nicotine administration also did not affect serum T3, TSH, or cholesterol concentrations, liver and kidney 5'D-I activity, and hepatic malic enzyme activity in L-T4-treated thyroidectomized rats. These studies provide strong evidence that nicotine is not responsible for the observed adverse effects of smoking on the thyroid in humans.

Iodine-induced hyperthyroidism: occurrence and epidemiology

We have critically reviewed the available information on iodine-induced hyperthyroidism (IIH) from published sources and other reports as well as the experience of the authors in Tasmania, Zaire, Zimbabwe, and Brazil. Administration of iodine in almost any chemical form may induce an episode of thyrotoxicosis (IIH). This has been observed in epidemic incidence in several countries when iodine has been given as prophylaxis in a variety of vehicles, but the attack rate as recorded has been low. IIH is most commonly encountered in older persons with long standing nodular goiter and in regions of chronic iodine deficiency, but instances in the young have been recorded. It customarily occurs after an incremental rise in mean iodine intake in the course of programs for the prevention of iodine deficiency, or when iodine-containing drugs such as radiocontrast media or amiodarone are administered. The biological basis for IIH appears most often to be mutational events in thyroid cells that lead to autonomy of function. When the mass of cells with such an event becomes sufficient and iodine supply is increased, the subject may become thyrotoxic. These changes may occur in localized foci within the gland or in the process of nodule formation. IIH may also occur with an increase in iodine intake in those whose hyperthyroidism (Graves' disease) is not expressed because of iodine deficiency. The risks of IIH are principally to the elderly who may have heart disease, and to those who live in regions where there is limited access to medical care. More information is needed on the long-term health impact of IIH or "subclinical" IIH, especially in the course of prophylaxis programs with iodized salt or iodinated oil in regions where access to health care is limited.

Comparison of administration of recombinant human thyrotropin with withdrawal of thyroid hormone for radioactive iodine scanning in patients with thyroid carcinoma

BACKGROUND

To detect recurrent disease in patients who have had differentiated thyroid cancer, periodic withdrawal of thyroid hormone therapy may be required to raise serum thyrotropin concentrations to stimulate thyroid tissue so that radioiodine (iodine-131) scanning can be performed. However, withdrawal of thyroid hormone therapy causes hypothyroidism. Administration of recombinant human thyrotropin stimulates thyroid tissue without requiring the discontinuation of thyroid hormone therapy.

METHODS

One hundred twenty-seven patients with thyroid cancer underwent whole-body radioiodine scanning by two techniques: first after receiving two doses of thyrotropin while thyroid hormone therapy was continued, and second after the withdrawal of thyroid hormone therapy. The scans were evaluated by reviewers unaware of the conditions of scanning. The serum thyroglobulin concentrations and the prevalence of symptoms of hypothyroidism and mood disorders were also determined.

RESULTS

Sixty-two of the 127 patients had positive whole-body radioiodine scans by one or both techniques. The scans obtained after stimulation with thyrotropin were equivalent to the scans obtained after withdrawal of thyroid hormone in 41 of these patients (66 percent), superior in 3 (5 percent), and inferior in 18 (29 percent). When the 65 patients with concordant negative scans were included, the two scans were equivalent in 106 patients (83 percent). Eight patients (13 percent of those with at least one positive scan) were treated with radioiodine on the basis of superior scans done after withdrawal of thyroid hormone. Serum thyroglobulin concentrations increased in 15 of 35 tested patients: 14 after withdrawal of thyroid hormone and 13 after administration of thyrotropin. Patients had more symptoms of hypothyroidism (P<0.001) and dysphoric mood states (P<0.001) after withdrawal of thyroid hormone than after administration of thyrotropin.

CONCLUSIONS

Thyrotropin stimulates radioiodine uptake for scanning in patients with thyroid cancer, but the sensitivity of scanning after the administration of thyrotropin is less than that after the withdrawal of thyroid hormone. Thyrotropin scanning is associated with fewer symptoms and dysphoric mood states.

Effects of excess iodine administration on thyroid function in euthyroid patients with a previous episode of thyroid dysfunction induced by interferon-alpha treatment

OBJECTIVE

To determine the effects of pharmacological quantities of iodide (SSKI) on thyroid function in euthyroid patients previously treated with recombinant interferon-alpha (rIFN-alpha) for chronic viral hepatitis B and C (HCV), a cytokine which may induce thyroid dysfunction.

DESIGN

Thyroid function tests were carried out in 16 euthyroid patients, 8 of whom had previously developed thyroid dysfunction during rIFN-alpha therapy for HCV, before, during and after the administration of 10 drops of saturated solution of potassium iodide (SSKI) (approximately 350 mg iodide).

PATIENTS

All 16 patients had been treated in the past with rIFN-alpha for HCV. Eight patients had developed rIFN-alpha induced abnormalities in thyroid function (5 inflammatory thyrotoxicosis, 1 Graves' disease, and 2 impaired thyroid organification of iodide) and 8 had not developed thyroid dysfunction.

MEASUREMENTS

After baseline serum free T4 (FT4) and free T3 (FT3) concentrations, basal and TRH stimulated TSH concentrations, and TSH-receptor (TSH-R-Ab) and thyroid peroxidase (TPO-Ab) antibodies were measured, 10 drops saturated solution of potassium iodide (SSKI, approximately 350 mg iodide) were given daily for 60 days and the above parameters assessed during and after SSKI was discontinued.

RESULTS

Five of 8 patients with a previous history of rIFN-alpha induced thyroid dysfunction developed mild iodide induced abnormalities of thyroid function (subclinical hypothyroidism (slightly elevated basal and TRH stimulated serum TSH concentrations with normal serum FT4 and FT3 concentrations) or hyperthyroidism) compared with the 8 patients who had no previous evidence of thyroid dysfunction during rIFN-alpha therapy.

CONCLUSIONS

In view of the present observations, it is prudent to avoid the administration of excess iodine to euthyroid subjects with a previous episode of thyroid dysfunction during rIFN-alpha therapy, adding a new group of patients susceptible to iodine induced thyroid disease.

Recombinant human thyrotropin is a potent stimulator of thyroid function in normal subjects

Recombinant human TSH (rhTSH) is known to stimulate 131I uptake and thyroglobulin (Tg) release from the postoperative remnant and metastases in thyroid cancer patients, but its effects on serum thyroid hormone and Tg concentrations in normal subjects have not been reported. Before using rhTSH in the management of thyroid disorders other than cancer, the thyroid response to rhTSH in normal subjects must be assessed. Six subjects, two men and four women, without evidence of thyroid disease, including normal serum free T4 index and TSH concentrations and negative tests for antithyroid peroxidase and Tg, were studied. Each received 0.1 mg rhTSH, im, 11% of the lowest dose that has been administered to thyroid cancer patients. Blood was obtained before; 2, 4, and 8 h after; and 1, 2, 3, 4, 7, and about 3 weeks after rhTSH administration. Serum TSH significantly increased at 2 h (mean +/- SE, 2.4 +/- 0.9 to 40.7 +/- 7.4 mU/mL), peaked at 4 h (50.9 +/- 9.3), remained significantly elevated for 1 day, and was significantly below baseline (0.8 +/- 0.5) 7 days after rhTSH administration. Serum T3 increased significantly at 4 h (115 +/- 4 to 190 +/- 14 ng/dL), peaked at 24 h (217 +/- 23 ng/dL), and remained significantly elevated for 3 days (151 +/- 12 ng/dL). Serum T4 increased significantly at 8 h (7.3 +/- 0.2 to 9.8 +/- 0.4 micrograms/dL), peaked at 24 h (11.2 +/- 0.5 micrograms/dL), and remained significantly elevated for 4 days (9.4 +/- 0.5 micrograms/dL). Serum Tg did not change for the first 8 h, increased significantly at 1 day (15.9 +/- 3.9 to 34.7 +/- 6.0 ng/mL), peaked at 2 days (44.2 +/- 7.0 ng/mL), and remained significantly elevated for 4 days (37.7 +/- 13.7 ng/mL). All values returned to baseline at 3 weeks. TSH antibodies were not detected at 3 weeks. A single dose of 0.1 mg rhTSH is a potent stimulator of thyroid function in normal subjects. rhTSH may be a useful agent to test thyroid reserve and for use in clinical settings that require direct thyroid stimulation.

Routine skin cleansing with povidone-iodine is not a common cause of transient neonatal hypothyroidism in North America: a prospective controlled study

A high incidence of transient neonatal hypothyroidism has been observed in premature infants after routine skin cleansing with iodine. Because these reports have been predominantly from Europe, a borderline, iodine-deficient area, we wished to determine whether this was also true in North America, an iodine-sufficient area. A prospective, controlled study was performed in premature babies < or = 36 weeks gestation admitted to a neonatal intensive care nursery. Thyroxine (T4) and thyrotropin (TSH) were measured at day 1, days 4 to 6, and 10 to 12 after skin preparation with iodine or with a noniodine-containing antiseptic solution (chlorhexidine) that served as control. If repeat cleansing was required, this sequence was repeated. Urinary iodine was quantitated on days 1 to 3 to estimate iodine exposure. There was no difference in the mean T4 concentration at any of the time points evaluated nor in the incidence of transient hypothyroidism between the iodine-exposed (2/17) and control babies (0/14) despite urinary iodine excretion up to 88 times the control value. Unexpectedly 5 iodine-exposed but 0 control babies developed severe hypothyroxinemia (T4 < 40 nmol/L), compatible with the sick euthyroid syndrome; one of them died. We conclude that, unlike in Europe, transient hypothyroidism is not a common sequela of routine skin cleansing with iodine in premature newborn infants in North America. This difference in incidence may be due to prior iodine status. Whether excessive iodine absorption in premature infants is associated with thyroid-independent toxic effects remains to be clarified.

Site selectivity of osteoblast gene expression response to thyroid hormone localized by in situ hybridization

We have previously reported that thyroid-stimulating hormone (TSH)-suppressive doses of L-thyroxine (L-T4) decrease femoral, but not vertebral, bone mineral density (BMD) in rats. L-T4-induced decreases in BMD were associated with increased expression of genes, reflecting osteoblast activity in mRNA extracted from whole femurs but not from vertebrae. To document that this skeletal selectivity reflected altered osteoblast activity, we studied gene expression by in situ hybridization in 8-wk-old rats treated with L-T4 (20 microg x 100 g body wt(-1) x day(-1)) for 4 wk. TSH-suppressive doses of L-T4 were associated with decreased femoral (0.299 +/- 0.005 vs. 0.273 +/- 0.005 g/cm2, P < 0.01), but not vertebral (0.222 +/- 0.004 vs. 0.218 +/- 0.003 g/cm2), BMD. In situ hybridization documented that L-T4 administration for 4 wk increased expression of osteocalcin and alkaline phosphatase mRNA in femoral, but not vertebral, osteoblasts. This study demonstrates a differential gene expression response of vertebral and femoral osteoblasts to L-T4. This altered degree of gene expression markers of osteoblast activity documented by in situ hybridization may in part explain the apparent clinical differences in the effect of L-T4 on femoral and vertebral BMD.

Mild clinical expression of myasthenia gravis associated with autoimmune thyroid diseases

Myasthenia gravis (MG) may occur in association with autoimmune thyroid diseases (AITD). The aim of this study was to evaluate the features of MG associated with AITD compared to those of MG without AITD. A total of 129 MG patients (34 men and 95 women; age range, 11-81 yr) were subdivided into: group A, 56 MG patients with AITD [25 with autoimmune thyroiditis and 31 with Graves' disease (GD)]; group B, 21 MG patients with nonautoimmune thyroid diseases; and group C, 52 MG patients without thyroid disease. The severity of MG was ranked according to the Osserman score. Laboratory evaluation included assays for antithyroid and antiacetylcholine receptor (AchRAb) antibodies. Ocular MG (Osserman's class 1) was more frequent in group A (41.0%) than in group B (14.2%; P < 0.03) or C (21.4%; P < 0.03). Severe generalized MG (classes > or = 2B) was more frequent in groups B (57.1%; P < 0.03) and C (51.9%; P < 0.02) than in group A (28.5%). GD patients with clinical evidence of ophthalmopathy had a higher frequency (P = 0.05) of ocular MG (57.8%) than GD patients without clinical ophthalmopathy (16.6%). Thymic disease was less frequent in group A (26.7%) than in group B (71.4%; P = 0.001) or C (59.7%; P = 0.001). The prevalence of thymic hyperplasia was 17.8%, 38.0%, and 40.3% in groups A, B, and C, respectively; the prevalence of thymoma was 8.9%, 33.4%, and 19.4%. When only patients with generalized MG were considered, thymic disease was less frequent (P < 0.02) in group A (40.6%) than in the remaining groups (69.4%). AchRAb was more frequent in groups B (57.1%) and C (57.6%; P < 0.03) than in group A (35.7%). In conclusion, MG associated with AITD has a mild clinical expression, with preferential ocular involvement and lower frequency of thymic disease and AchRAb. This supports the hypothesis that ocular and generalized MG are separate diseases with different spectra of associated diseases. Nonautoimmune thyroid diseases have no influence on the features of MG. The association of ocular MG and AITD might be due to a common autoimmune mechanism and/or a peculiar genetic background.

Bilateral cervical plexus block for thyroidectomy and parathyroidectomy in healthy and high risk patients

We evaluated the benefits of bilateral deep cervical plexus block regional anesthesia in healthy and high risk patients undergoing thyroid and parathyroid surgery and assessed its effects on respiratory function. Twenty-one patients undergoing thyroid and parathyroid operations were studied. Bilateral superficial and deep plexus blocks were performed in all patients except one (who received only superficial plexus block because of a slightly prolonged prothrombin time) with 0.375-0.5% bupivacaine with 1:200,000 epinephrine. Intraoperatively, supplemental intravenous sedatives/narcotics were titrated to achieve patient comfort and cooperation. To allay anxiety, patients were allowed to listen to music via headphones intraoperatively. Forced vital capacity was measured before block, 10 minutes after the block and in the recovery room in half the patients. Eighteen patients tolerated the procedure well with supplemental sedation. Two patients required supplemental inhalation anesthesia via mask and one required tracheal intubation because of coughing prior to surgery. Three high risk patients tolerated the procedure well requiring only intraarterial line monitoring. Postoperatively, 11 patients had minimal incisional pain, 13 patients had mild pain on swallowing and 2 patients complained of nausea. There were no significant differences in the baseline forced vital capacity vs. forced vital capacity measured after the block and in the recovery room. This study indicates that regional anesthesia is an appropriate alternative to general anesthesia in selected patients undergoing thyroid and parathyroid surgery and did not compromise respiratory function.

Effects of ceramide and protein kinase C on the regulation of type I 5'-deiodinase in FRTL-5 rat thyroid cells

Tumor necrosis factor-alpha (TNF alpha) is a pleiotropic cytokine that is involved in the regulation of thyroid growth and differentiated functions. The cellular and molecular mechanisms involved in mediating the effects of TNF alpha on thyroid function, however, are unknown. In a number of cell types, TNF alpha receptor binding results in the activation of specific signal transduction cascades, including protein kinase C (PKC) and the hydrolysis of sphingomyelin to ceramide. In the present study, we examined the possible role of PKC and the hydrolysis of sphingomyelin to ceramide in the regulation of TSH-induced increases in 5'-deiodinase (5'D-I) activity and 5'D-I messenger RNA (mRNA) levels in FRTL-5 cells. Further, we have recently shown that TNF alpha and interferon-gamma (IFN gamma) act synergistically to block TSH-induced increases in type I 5'D-I activity and 5'D-I gene expression in FRTL-5 rat thyroid cells. Thus, we tested the hypothesis that the activation of one or both pathways is involved in synergistic effect of TNF alpha and IFN gamma on thyroid function. In TSH-stimulated FRTL-5 cells, the addition of 12-O-tetradecanoylphorbol 13-acetate (TPA), an activator of PKC, inhibited TSH-induced increases in 5'D-I activity and 5'D-I mRNA levels in a dose-dependent manner. Incubation of FRTL-5 cells with TPA and a minimal effective concentration of IFN gamma (12.5 U/ml) in combination, however, failed to result in a synergistic inhibition of the TSH-induced increase in 5'D-I activity or 5'D-I mRNA levels. Similarly, incubation of FRTL-5 cells with sphingomyelinase (SMase), which converts sphingomyelin to ceramide, inhibited TSH-induced increases in 5'D-I activity and 5'D-I mRNA levels in a dose-dependent manner. Coincubation of FRTL-5 cells with SMase and IFN gamma failed to show a synergistic inhibition of the TSH-induced increase in 5'D-I activity or 5'D-I mRNA levels. Further, incubation of FRTL-5 cells with TPA plus SMase in the presence of IFN gamma failed to result in the synergistic inhibition of TSH-induced increases in 5'D-I activity or 5'D-I mRNA levels. The effect of TPA and SMase on TSH-induced cAMP production was examined. Low concentrations of TPA, which inhibit TSH-induced 5'D-I activity, failed to inhibit TSH-induced cAMP production or the cAMP-induced increase in 5'D-I activity. In contrast, SMase inhibited TSH-induced cAMP production in a dose-dependent manner. In the presence of IFN gamma, however, activation of either or both pathways is not sufficient to result in a synergistic inhibition of 5'D-I activity or 5'D-I gene expression. Together, our results suggest that TNF alpha-induced activation of PKC and hydrolysis of sphingomyelin can inhibit thyroid cell function. The activation of additional signal transduction pathways, however, by TNF alpha is required for the synergistic inhibition of thyroid function by TNF alpha and IFN gamma.

Multiple changes in thyroid function in patients with chronic active HCV hepatitis treated with recombinant interferon-alpha

OBJECTIVE

Recombinant human interferon-alpha (r-IFN-alpha) is often successfully used in the treatment of patients with chronic viral hepatitis B and C. Thyroid dysfunction has been reported to occur with variable frequency during r-IFN-alpha therapy especially in patients with preexisting thyroid autoimmunity. We have prospectively evaluated the effect of r-IFN-alpha on various aspects of thyroid function in patients with HCV chronic hepatitis.

DESIGN

Thirty-two patients with HCV chronic active hepatitis were studied prospectively before and during r-IFN-alpha therapy. Serum TSH, FT4, FT3, and thyroid receptor (TSR) and thyroid peroxidase (TPO) antibodies, and the iodide-perchlorate discharge test (I-C10(4)) to detect subtle defects in the thyroid organification of iodide were carried out during the study. Thyroid radioactive iodine uptakes (RAIU) were obtained in patients who developed thyrotoxicosis.

RESULTS

All patients were clinically and biochemically euthyroid prior to r-IFN-alpha therapy with negative I-C10(4) discharge tests. Four patients became thyrotoxic, 3 secondary to destructive or inflammatory thyroiditis with a low thyroid RAIU, and 1 patient developed hypothyroidism. The I-C10(4) discharge test became positive in 7 of the 32 patients studied prospectively; 5 of these patients did not develop other evidence of thyroid dysfunction and did not have positive TPO antibodies. In these 5 patients the test became negative after r-IFN-alpha was discontinued. Appropriate therapy of the patients with thyrotoxicosis (methylprednisolone for 3 patients with destructive thyroiditis and methimazole for 1 patient with hyperthyroidism) or with hypothyroidism (L-thyroxine) was successful.

CONCLUSIONS

Thyroid dysfunction, especially destructive or silent thyroiditis resulting in thyrotoxicosis, is not infrequently observed in patients receiving r-IFN-alpha therapy for chronic active hepatitis. Although underlying autoimmune thyroid disease appears to predispose patients to develop thyroid dysfunction, other patients become thyrotoxic or hypothyroid in the absence of baseline positive TPO-Ab. Subtle defects in the thyroidal organification of iodine as determined by the I-C10(4) discharge test, in the absence of autoimmune thyroid disease, was observed in 5 patients who remained euthyroid, suggesting that r-IFN-alpha directly reduces the intrathyroidal organification of iodine.

Treatment guidelines for patients with thyroid nodules and well-differentiated thyroid cancer. American Thyroid Association

A set of minimum clinical guidelines for use by primary care physicians in the evaluation and management of patients with thyroid nodules or thyroid cancer was developed by consensus by an 11-member Standards of Care Committee (the authors of the article) of the American Thyroid Association, New York, NY. The participants were selected by the committee chairman and by the president of the American Thyroid Association based on their clinical experience. The committee members represented different geographic areas within the United States, to reflect different practice patterns. The guidelines were developed based on the expert opinion of the committee participants, as well as on previously published information. Each committee participant was initially assigned to write a section of the document and to submit it to the committee chairman, who revised and assembled the sections into a complete draft document, which was then circulated among all committee members for further revision. Several of the committee members further revised and refined the document, which was then submitted to the entire membership of the American Thyroid Association for written comments and suggestions, many of which were incorporated into a final draft document, which was reviewed and approved by the Executive Council of the American Thyroid Association.

Lack of increased serum interleukin-6 and soluble IL-6 receptor concentrations in patients with thyroid diseases following recombinant human interferon alpha therapy

BACKGROUND

Serum interleukin-6 (IL-6) concentrations are frequently elevated in inflammatory thyroid diseases, such as subacute thyroiditis and amiodarone induced thyroiditis. We and others have recently observed that recombinant interferon-alpha (rIFN-alpha) therapy for chronic, active viral hepatitis and malignant disorders may induce thyroid dysfunction, including thyrotoxicosis secondary to thyroiditis. Serum IL-6 and its soluble receptor (sIL-6R) have been measured for the first time in patients with chronic active hepatitis receiving rIFN-alpha therapy.

METHODS

Studies were carried out in 37 patients treated with rIFN-alpha for chronic, active viral hepatitis. Thyroid function tests and serum IL-6 and sIL-6R were measured before and during rIFN-alpha therapy.

RESULTS

Six patients developed inflammatory or destructive thyrotoxicosis confirmed by elevated serum free T4 or free T3 concentrations, suppressed serum thyroid-stimulating hormone (TSH) values, and a low thyroid radioactive iodine uptake. Serum IL-6 and sIL-6R concentrations were not elevated in these patients with rIFN-alpha-induced thyroiditis.

CONCLUSIONS

These results suggest that serum IL-6 concentrations are not useful in differentiating between inflammatory thyrotoxicosis and hyperthyroidism induced by rIFN-alpha therapy as is the case in amiodarone-induced thyrotoxicosis. It is possible that rIFN-alpha therapy could be associated with an inhibitory effect of rIFN-alpha on the release of IL-6 from damaged thyroid cells and not on the basal secretion of IL-6.

Inflammatory thyroid disorders

Inflammatory disorders of the thyroid, including autoimmune thyroiditis, are among the most common endocrine abnormalities encountered in clinical practice. The association of pain with these disorders, however, is relatively uncommon. Despite this observation, painful thyroid disorders comprise a significant component of the spectrum of thyroid disease. A rational approach to such patients, including history, physical examination, laboratory evaluation, radionuclide or ultrasonographic imaging, and fine needle aspiration biopsy, will allow the appropriate diagnosis to be made in the vast majority of cases.

Increased serum concentrations of interleukin-6 (IL-6) and soluble IL-6 receptor in patients with Graves' disease

Increased serum interleukin-6 (IL-6) concentrations have been reported in patients with thyroid destructive processes. In the present study we measured IL-6 and soluble IL-6 receptor (sIL-6R) concentrations in the serum of normal subjects and patients with Graves' disease using a high sensitivity sandwich enzyme-linked immunoassay. We found increased serum IL-6 and sIL-6R concentrations (69.3 fmol/L, and 964 pmol/L, respectively) in 49 hyperthyroid patients with Graves' disease (GD) compared to those in controls [55.8 fmol/L (P = 0.019) and 772 pmol/L (P = 0.007), respectively]. In 31 newly diagnosed GD patients, serum concentrations of IL-6 and sIL-6R during the hyperthyroid phase were elevated, and after therapy with methimazole only, serum sIL-6R concentrations returned to normal (940 vs. 726 pmol/L; P < 0.001) but serum IL-6 did not. Serum sIL-6R concentrations (mean +/- 2 SD) were higher in GD patients with active inflammatory thyroid-associated ophthalmopathy than those in patients with inactive or absent thyroid-associated ophthalmopathy (P < 0.05). In conclusion, we have demonstrated activation of the IL-6 system in GD and, for the first time, have measured and found increased serum sIL-6R concentrations in hyperthyroid GD patients.

Comparison of the effects of propylthiouracil and selenium deficiency on T3 production in the rat

Selenium deficiency and propylthiouracil (PTU) treatment both decrease hepatic type I T4 5'-deiodinase activity (5'D-I), which is considered to be an important regulator of the serum T3 derived from peripheral T4 to T3 conversion (T3 neogenesis). The effects of PTU treatment or a selenium-deficient diet on T4 and T3 kinetics were compared in thyroid-ablated rats infused with stable T4 to determine whether PTU treatment is a more potent inhibitor of T3 neogenesis than selenium deficiency and to compare the degree of inhibition of T3 production with the degree of inhibition of 5'D-I. PTU treatment and selenium deficiency (Se-) did not affect the T3 MCR (control, 46.0 +/- 2.5; PTU, 41.7 +/- 2.8; Se-, 41.1 +/- 4.0 ml/h.100 g BW), but did reduce serum T3 concentrations by 29% and 25%, respectively (control, 58.7 +/- 2.6; PTU, 41.5 +/- 1.0; Se-, 43.9 +/- 2.7 ng/dl; P < 0.01 for PTU or Se- vs. control) and the T3 production rate by 35% and 32%, respectively (control, 26.6 +/- 1.0; PTU, 17.3 +/- 2.0; Se-, 18.0 +/- 1.9 ng/h.100 g BW; P < 0.01 for PTU or Se- vs. Control). PTU treatment and selenium deficiency significantly increased serum T4 concentrations by 36% and 32%, respectively, due to a decrease in T4 MCR (control, 1.4 +/- 0.1; PTU, 1.1 +/- 0.1; Se-, 1.1 +/- 0.04 ml/h.100 g BW; P < 0.05 for PTU or Se- vs. control). Assuming that the concentration of T4 available for T3 neogenesis is proportional to the serum T4 concentration, the increase in serum T4 concentrations caused by PTU treatment or Se- would probably have proportionally increased the rate of T3 neogenesis. Based on these considerations, the apparent decrease in T3 neogenesis in the PTU-treated animals was 52%. This is less than the 79% and 67% inhibition of 5'D-I noted, respectively, in the liver and kidneys of these rats. Similarly, the apparent decrease in T3 neogenesis in the Se- rats was 48%, again less than the 85% and 64% inhibition of 5'D-I in their liver and kidneys, respectively. These studies suggest that PTU and Se- have similar effects on T3 neogenesis. The more potent effects of these treatments on liver and kidney 5'D-I activities than on T3 neogenesis suggest that the activities of these enzymes in these tissues are not the only important determinants of the serum T3 that is derived from nonthyroidal sources.

Thymic uptake of iodine-131 in the anterior mediastinum

Two thyroidectomized patients with a history of differentiated thyroid carcinoma are presented who had nonmetastatic mediastinal 131I uptake following therapeutic doses of 131I. Chest CT scans in both patients demonstrated an anterior mediastinal mass. Surgical excision in one patient and a percutaneous CT-guided fine needle aspiration biopsy in the other disclosed normal thymus tissue. Iodine-131 uptake in the anterior mediastinum in patients thyroidectomized for follicular or papillary thyroid carcinoma may represent the thymus.

Differential responses of femoral and vertebral bones to long-term excessive L-thyroxine administration in adult rats

Recent studies suggest that thyroid-stimulating hormone suppressive doses of thyroid hormone decrease bone mass in humans and growing rats. To determine the long-term effects of excessive L-thyroxine administration on the femur and vertebrae in an adult rat model, 20 male Sprague-Dawley rats (20 weeks old) were randomized into two groups. Group 1 received L-thyroxine (20 micrograms/100 g body weight ip daily), and group 2 received normal saline ip daily for 20 weeks. Femoral and lumbar vertebral bone mineral density measurements were performed at 0, 6, 15, 18 and 20 weeks of treatment. After 20 weeks of treatment, total RNA was isolated from both femoral and lumbar bones. Northern hybridization was performed with 32P-labeled DNA probes for osteocalcin, osteopontin, alkaline phosphatase and tartrate-resistant acid phosphatase. Significant decreases in bone mineral density in the femur of L-thyroxine-treated rats were observed after 15 weeks (p < 0.03). Lumbar bone mineral density was not affected. Both osteoblast (osteocalcin, osteopontin, alkaline phosphatase) and osteoclast (tartrate-resistant acid phosphatase) gene expression markers were increased significantly in the femoral bone (p < 0.001), but not in the lumbar vertebrae of the L-thyroxine-treated rats. We conclude that long-term administration of excessive doses of L-thyroxine to the adult rat preferentially affects femoral but not vertebral bone. This is manifested by decreased bone mineral density as well as increased gene expression markers for osteoblast and osteoclast activity in the femur.