Low prevalence of thyrotropin receptor antibody in primary hypothyroidism in Japan.

The prevalence of TSH receptor antibody (TRAb), measured by RRA assay (TSH-binding inhibitor immunoglobulin, TBII) and biological stimulation-blocking assay (thyroid-stimulation blocking antibody, TSBAb), was examined in 134 consecutive patients with primary hypothyroidism due to autoimmune thyroiditis [83 patients with goitrous Hashimoto's disease (group A) and 51 with primary atrophic hypothyroidism (group B)]. In group A, TBII was detected in 6 patients (7%), TSBAb in 7 (8%), and both in 4 (5%). Similarly, in group B, TBII was detected in 7 patients (14%), TSBAb in 7 (14%), and both in 5 (10%). TBII with TSBAb activity was low or moderate in group A, but strongly positive in group B. No relationship was apparent in either group between TBII or TSBAb activity and any clinical or laboratory parameter examined. Moreover, no clinical or laboratory findings distinguished patients with TRAb from those without. The low prevalence of TRAb in primary hypothyroidism suggests that intrathyroidal cell-mediated destructive mechanisms may be more important in the pathogenesis of hypothyroidism in autoimmune thyroiditis.

Increased serum concentration of soluble CD30 in patients with Graves' disease and Hashimoto's thyroiditis.

This study investigated serum levels of the soluble form of CD30 (sCD30), which is mainly secreted from T helper 2(Th2) cells, in autoimmune thyroid diseases. The possible relationship of sCD30 to autoantibody production was also evaluated. Serum levels of sCD30 were determined by an enzyme-linked immunosorbent assay in 71 patients with Graves' disease, 37 patients with Hashimoto's thyroiditis, and 21 normal donors. Compared with normal subjects (7.1 +/- 4.5 U/mL), sCD30 was increased in patients with Graves' disease (29.2 +/- 25.2 U/mL, P < 0.0001) and in patients with Hashimoto's thyroiditis (29.9 +/- 26.9 U/mL, P < 0.0001). In Graves' disease, sCD30 levels were higher in thyrotoxic patients (41.7 +/- 31.2 U/mL, P < 0.001) than in remission patients (15.8 +/- 11.0 U/mL), and a significant correlation was observed between sCD30 levels and serum activities of TSH receptor antibody (r = 0.444, P < 0.0001). In Hashimoto's thyroiditis, sCD30 levels were higher in patients with transient destructive thyrotoxicosis caused by the aggravation of the disease (48.8 +/- 34.4 U/mL, P < 0.05) than in euthyroid patients (24.2 +/- 19.4 U/mL). These data suggest that serum sCD30 is a valuable marker of disease activity and support an important role of the Th2-type immune response in the pathogenesis in Graves' disease and Hashimoto's thyroiditis.

Pathogenic role of asialo human chorionic gonadotropin in gestational thyrotoxicosis.

We reported that gestational thyrotoxicosis is induced by thyroid-stimulating activity (TSA) of circulating hCG. However, the serum immunological hCG concentration did not correlate to TSA. To elucidate this, we examined the relation of carbohydrate moieties of hCG to bioactivity in 79 early pregnant women, divided into 4 groups: no emesis, mild emesis, hyperemesis, and gestational thyrotoxicosis with hyperemesis. Serum free T4 (FT4) and free T3 (FT3) levels were significantly higher and TSH was lower in the hyperemesis (FT4, 23.42 +/- 5.02 pmol/L; FT3, 6.26 +/- 1.80 pmol/L; TSH, 0.30 +/- 0.44 mU/L) and in gestational thyrotoxicosis (FT4, 48.65 +/- 14.80 pmol/L; FT3, 14.71 +/- 3.47 pmol/L; TSH, < 0.04 mU/L) groups than in the no emesis group (FT4, 16.99 +/- 2.48 pmol/L; FT3, 5.51 +/- 0.75 pmol/L; TSH, 1.37 +/- 1.23 mU/L; P < 0.0005). TSA was also significantly higher in the hyperemesis (566 +/- 187%) and gestational thyrotoxicosis (832 +/- 168%) groups than in the no emesis group (321 +/- 135%). We found no significant difference among serum hCG concentrations measured by immunoassay in the four groups. To characterize the carbohydrate chains, serum hCG was fractionated by Concanavalin-A and ricin lectin affinity chromatography. The fraction firmly bound to Con-canavalin-A, which contains hCG with high mannose and hybrid-type carbohydrate chains, was significantly higher in the hyperemesis group (91.07 +/- 2.06%; n = 15) than in the no emesis group (89.61 +/- 2.38%; n = 24; P < 0.04). The fraction firmly bound to ricin column, which contains hCG with asialo-carbohydrate chains, was significantly increased in the gestational thyrotoxicosis group (3.44 +/- 1.70%; n = 5) compared with that in the no emesis group (1.77 +/- 0.49%; n = 24; P < 0.03). Serum FT4 positively correlated to the hCG fraction firmly bound to ricin column (r = 0.61; P < 0.001). We conclude that thyrotoxicosis with hyperemesis may be caused by circulating asialo-hCG with higher thyrotropic bioactivity.

Distribution of patients' test values and applicability of "average of normals" method to quality-control of radioimmunoassays.

Applicability of the Hoffmann's average of normals (Mn) method was evaluated in quality control (QC) of radioimmunoassays (RIA) for thyroxine, 3,5,3'-tri-iodothyronine, thyrotropin, and insulin--assays that are performed routinely in the authors' laboratory. In the first three RIAs, the patterns of the distributions were almost constant and Mn showed significant correlations with values of QC sera and intercepts of the dose-response curve. In insulin RIA, the patterns varied appreciably and Mn showed correlations with parameters that reflect a disturbance in the distribution. Exclusion of assays with abnormal distributions, however, resulted in better correlations of Mn with other QC parameters. These results suggest that average of normals method can be a very useful adjunct to conventional QC methods for RIA. The possibility that the method may be affected by a disturbance in the distribution can be monitored by computation of parameters reflecting such disturbance.

New indices for thyroid functional status, hormone binding, and peripheral hormone metabolism. Principal component analysis of 24,000 clinical data.

Principal component analysis of three thyroid function tests, thyroxine (T4), 3,5,3'-triiodothyronine (T3), and T3 uptake (T3U), was done using 24,000 data obtained from patients with a wide range of pathophysiologic conditions related to the thyroid. The three component scores were obtained as follows: Z1 = 2.62 square root T4 + 0.63 square root T3 + 3.18 square root T3U - 32.43; Z2 = 0.91 square root T4 + 0.24 square root T3 - 4.68 square root T3U + 20.14; and Z3 = 3.94 square root T4 + 0.95 square root T3 + 0.18 square root T3U - 1.53 (T4 micrograms/dL, T3 ng/dL, T3U%). The first component (Z1) represents an apparent axis to the direction of thyroid functional status. It provides a new metabolic index putting conventional free T4 and free T3 indices together. The second component (Z2) was found to be a sensitive indicator of abnormal hormone binding. It showed a close correlation with serum concentration of thyroxine-binding globulin. The third component (Z3) represents the degree of T3 predominance over T4. Computation of these scores will facilitate the diagnosis of atypical cases in which hyper-or hypothyroidism is complicated by abnormal peripheral hormone binding and/or metabolism.

Thyroxine requirement during pregnancy for replacement therapy of hypothyroidism.

We examined the dose requirements of thyroxine (T4) and desiccated thyroid during eight pregnancies of six women who had undergone total thyroidectomy for thyroid carcinoma. In five pregnancies from four patients treated with T4, serum free T4, which was measured by a newly developed radioimmunoassay, decreased during pregnancy but increased above the normal range after delivery. Consistent with these changes in free T4, serum TSH (measured by a highly sensitive immunoradiometric assay) increased during pregnancy but returned to an undetectable level after delivery, with one exception. The serum triiodothyronine (T3)-to-T4 ratio, which is related to peripheral conversion of T4 to T3, was lower in patients treated with T4 than in normal controls, regardless of pregnancy. The ratio decreased further during pregnancy, and so relative deficiency of T3 during pregnancy was suspected, especially in T4-treated patients. On the other hand, in two pregnancies from two other patients treated with desiccated thyroid at a dose most equivalent to that of T4, serum free T4 decreased to a low-normal value during gestation but returned to the normal range after delivery, whereas serum TSH scarcely changed during pregnancy. These findings indicate that replacement therapy for pregnant patients with hypothyroidism after total thyroidectomy should include an increased dose of T4; in contrast, the dose of desiccated thyroid need not be changed.

Enzyme-linked immunosorbent assay for anti-tropomyosin antibodies and its clinical application to various heart diseases.

Tropomyosin is one of the key proteins for muscle contraction. We developed an enzyme-linked immunosorbent assay for antibodies to porcine muscle tropomyosin and measured serum anti-tropomyosin antibodies in patients with heart diseases and in normal controls. The mean values of absorbance in the ELISA assay of patients with ischemic heart disease (n=36, P<0.001), dilated cardiomyopathy (n=28, P<0.005), valvular heart disease (n=27, P<0.05), and collagen disease (n=38, P<0.05) were significantly higher than those of normal controls (n=53), but the value in patients with hypertrophic cardiomyopathy (n=19) was not significantly different from that of normal controls. When the cut-off value was fixed at the mean+2 SD of absorbance in normal controls, positive reactions were found in 19.4%, 7.1%, 18.5% and 15.8% of patients with ischemic heart disease, dilated cardiomyopathy, valvular heart disease, and collagen disease, respectively. An inhibition study revealed that anti-tropomyosin antibodies were different from anti-myosin antibodies, but there was a partial cross-reactivity between the two. Thus, there was a weak correlation of the titers of the two types of antibody within the group of heart diseases. These data indicate that measurement of anti-tropomyosin antibodies by ELISA is helpful for detecting autoimmune abnormalities in various heart diseases.

Differentiation of postpartum thyrotoxicosis by serum thyroglobulin: usefulness of a new multisite immunoradiometric assay.

Destruction-induced thyrotoxicosis and Graves' thyrotoxicosis must be differentiated, since they are treated differently. To find a useful marker, we examined serial changes in serum thyroglobulin (Tg) concentrations in 20 patients with postpartum thyroid disease (9, euthyroid Hashimoto's disease; 11, Graves' disease in remission in early pregnancy). Serum Tg was measured by a new multisite immunoradiometric assay that allows little influence of anti-Tg autoantibodies. Eight women developed destruction-induced thyrotoxicosis 1 to 4 months postpartum, 6 had relapse of Graves' thyrotoxicosis 2 to 4 months postpartum, and 6 remained euthyroid. In destruction-induced thyrotoxicosis, serum Tg 2 months before the onset was 13.3 +/- 11.4 micrograms/L, then clearly increased 1 month before (34.5 +/- 31.9 micrograms/L) and was even higher at the onset of thyrotoxicosis (116.5 +/- 137.1 micrograms/L). In contrast, serum Tg increased only at the onset in Graves' thyrotoxicosis (from 25.9 +/- 25.2 micrograms/L 1 month before to 76.1 +/- 75.3 micrograms/L at the onset, p < 0.05). There was no difference in serum Tg level at the onset between the two disorders. However, when data were expressed as the percent increase from the level one month before, and the cut-off value were taken at 150%, all 7 patients above the cut-off developed destruction-induced thyrotoxicosis, and 6 of 7 below had recurrent Graves' thyrotoxicosis. Thus, serial measurement of serum Tg is useful for the differentiation of destruction-induced thyrotoxicosis from Graves' thyrotoxicosis after delivery.

Increased serum concentration of interleukin-5 in patients with Graves' disease and Hashimoto's thyroiditis.

We investigated serum levels of interleukin-5 (IL-5) in order to examine the role of T-helper 2 (Th2)-type immune response in the pathogenesis of autoimmune thyroid diseases. Serum levels of IL-5 were determined by a highly sensitive sandwich enzyme-linked immunosorbent assay in 42 patients with Graves' disease, 32 patients with Hashimoto's thyroiditis, 12 patients with silent thyroiditis, and 21 normal controls. Compared with serum levels in normal subjects (5.8 +/- 4.2 pg/mL), IL-5 was increased in patients with Graves' disease (16.4 +/- 16.7 pg/mL, p < .01), and in patients with Hashimoto's thyroiditis (10.0 +/- 7.6 pg/mL, p < .05), but not in patients with silent thyroiditis. There was no correlation between serum free thyroxine (FT4) and IL-5 levels. These data suggest an important role of the Th2-type immune response in the pathogenesis of Graves' disease and Hashimoto's thyroiditis.

Novel thyrotropin (TSH)-TSH antibody complex in a healthy woman and her neonates.

A novel high-molecular-weight (MW) form of immunoreactive TSH [35,000 Da on Sephacryl S-200HR gel chromatography (S-200 chromatography)] was documented in a 32-year-old healthy woman who delivered two neonates with transient hyperthyrotropinemia. Her TSH levels ranged from 21.2 to 53.9 mU/L on different days or from 11.0 to 48.1 mU/L by the different immunoradiometric assay methods. The IgG fractions showed specific 125I-labeled hTSH binding and inhibited in vitro cAMP increase induced by hTSH but not that induced by bTSH. On protein G Superose HR affinity chromatography (protein G chromatography) equilibrated with 10 mmol/L sodium/potassium phosphate buffer (PB) followed by elution with 0.1mol/L glycine buffer, 95-99% of her TSH immunoreactivity eluted in the latter (bound) fraction while almost all was in the former (unbound) fraction in the control serum containing authentic hTSH. However, after dialysis of this bound fraction overnight with PB adding 0.5 mol/L NaCl (PB/NaCl), which exhibited greater ionic strength than PB, almost all TSH immunoreactivity changed from the bound fraction into the unbound fraction on the protein G chromatography equilibrated with PB/NaCl. These data indicate that the novel immunoreactive TSH was due to hTSH and hTSH-specific antibody complex, and dissociation of the complex may be incomplete on direct S-200. The immunoreactive TSH showed high MW form (35,000 Da). The dissociation may be almost complete during dialysis with greater ionic strength; the native TSH then appeared to be of formal size.

Onset of Graves' thyrotoxicosis after an attack of allergic rhinitis.

We previously reported that allergic rhinitis was an aggravating factor for Graves' disease and that thyrotoxicosis relapsed 2 months after an allergic attack. In this paper, we report a patient who showed onset of Graves' thyrotoxicosis after an attack of allergic rhinitis. The patient, a 30-year-old woman, was initially diagnosed with subclinical autoimmune thyroiditis. Interestingly, the patient showed weak activity of thyroid-stimulating antibody (TSAb), while TSH-binding inhibitory immunoglobulin (TBII) was negative and her thyroid function tests, including TSH, were completely normal. The patient developed severe allergic rhinitis in response to Japanese cedar pollen lasting from February until April in 1995 with an increase in serum antigen-specific immunoglobulin E and peripheral blood eosinophils. Two months later, she developed thyrotoxicosis in association with increase in TSAb and TBII. These findings suggest that allergic rhinitis not only aggravates Graves' disease but also induces the clinical onset of Graves' thyrotoxicosis.

CD30 expression and interleukin-4 and interferon-gamma production of intrathyroidal lymphocytes in Graves' disease.

We reported that serum levels of interleukin-5 (IL-5) and soluble CD30, mainly secreted from T helper 2 (Th2) cells, were increased in Graves' disease. To clarify the immune balance of Th1/Th2 within the Graves' thyroid gland, we have compared the expression of CD30, a preferential marker for T cells producing type 2 cytokines, and the production of interferon-gamma (IFN-gamma) and IL-4 between intrathyroidal lymphocytes (ITL) and peripheral blood lymphocytes (PBL). In PBL, none of these parameters were different between patients and normal subjects. The proportion of CD30+ cells in ITL was markedly higher (5.1%+/-2.8%, p < 0.0001) than that in patients' PBL (0.4%+/-0.3%). Likewise, both the proportions of IFN-gamma+ (14.8%+/-5.5%) and IL-4+ cells (2.4%+/-0.5%) in ITL were higher than those in PBL (9.6%+/-2.5%; p < 0.01, 1.5%+/-0.4%; p < 0.0001, respectively). The proportion of type 0 (both IFN-gamma and IL-4 positive, 1.0%+/-0.4% p < 0.001), type 1 (IFN-gamma positive, 14.0%+/-5.6%, p < 0.01) or type 2 cells (IL-4 positive, 1.4%+/-0.5%, p < 0.05) in ITL was significantly higher as compared with those in PBL (0.4%+/-0.1%, 9.0%+/-2.4%, 1.1%+/-0.3%, respectively). The ratios of ITL/PBL in CD30+ (23.3+/-30.6) and type 0 cells (2.5+/-1.2) were higher than the ratios in other subsets. The proportion of CD30+ cells correlated with the proportion of type 0 cells (r = 0.686, p < 0.01), but not with type 1 or type 2 cells. These findings suggest that there is no obvious deviation of Th2/Th1 profile in the Graves' thyroid gland, although intrathyroidal CD30+ T cells and Th0 cells may play some role in the development of autoimmune abnormalities in Graves' disease.

Increased serum concentration of interleukin-12 in patients with silent thyroiditis and Graves' disease.

We previously reported that interleukin-5 (IL-5), secreted from Th2 cells, was increased in patients with Graves' disease, but not in patients with silent thyroiditis. In this study, we investigated serum levels of interleukin-12 (IL-12) in order to examine the role of Th1-type immune response in the pathogenesis of autoimmune thyroid diseases. Serum levels of IL-12 were determined by a highly sensitive sandwich enzyme-linked immunosorbent assay in 68 patients with Hashimoto's thyroiditis (26 of whom had silent thyroiditis), 74 patients with Graves' disease, 8 patients with subacute thyroiditis, and 27 normal controls. Serum levels of IL-12 in thyrotoxic patients with silent thyroiditis (385.2 +/- 164.5 pg/mL, mean +/- SD), and in thyrotoxic patients with Graves' disease (343.6 +/- 163.8 pg/mL) were significantly increased compared with serum levels in normal subjects (163.9 +/- 66.8 pg/mL, p < 0.0001, p < 0.0001, respectively) or in thyrotoxic patients with subacute thyroiditis (241.9 +/- 46.5 pg/mL, p < 0.01, < 0.05, respectively). The ratio of IL-12 to IL-5 in thyrotoxic patients with silent thyroiditis (64.2 +/- 39.7) was significantly higher than that in normal controls (33.7 +/- 13.3, p < 0.01) or in thyrotoxic patients with Graves' disease (40.6 +/- 36.0, p < 0.05). These data suggest that Th1-type immune response is predominant in silent thyroiditis, and that not only Th2-type immune response but also Th1-type immune response is important in the pathogenesis of Graves' disease.

Serum concentration of soluble Fas in patients with autoimmune thyroid diseases.

Fas is an apoptosis-signaling receptor molecule found on the surface of a number of cell types. Malfunction of the Fas system accelerates autoimmune diseases, whereas its exacerbation may cause tissue destruction. Soluble Fas (sFas) molecule lacks the transmembrane domain due to alternative splicing and blocks Fas-mediated apoptosis. This study investigated serum levels of sFas in autoimmune thyroid diseases. Serum levels of sFas were determined by enzyme-linked immunosorbent assay in 46 patients with Graves' disease, 32 patients with Hashimoto's thyroiditis, 14 patients with silent thyroiditis, and 24 normal controls. Compared with normal subjects (1.43+/-0.37 ng/mL), sFas was increased in thyrotoxic patients with Graves' disease (1.89+/-0.47 ng/mL, p < 0.001), and was decreased in patients with Graves' disease in remission (1.02+/-0.41 ng/mL, p < 0.001) and in euthyroid patients with Hashimoto's thyroiditis (0.97+/-0.25 ng/mL, p < 0.0001), but was normal in hypothyroid patients with Hashimoto's thyroiditis and in thyrotoxic patients with silent thyroiditis. Thus, changes in serum levels of sFas could not be explained by changes in serum thyroid hormones, although sFas concentration correlated with free thyroxine (r = 0.692, p < 0.0001). Also, the levels of sFas significantly correlated with the activities of TSH receptor antibody in Graves' disease (r = 0.671, p < 0.0001). Increased sFas in Graves' disease suggests increased expression of alternatively spliced Fas mRNA variant that produces sFas protein and decreased of cell surface expression of Fas, and may induce thyroid cell growth and production of TSH receptor antibody by protecting against apoptosis of thyroid cells and autoreactive B cells. Decreased sFas in Hashimoto's thyroiditis suggests decreased Fas mRNA variant and increased full-length Fas mRNA and membrane Fas, and may induce destruction of thyroid cells by promoting apoptosis of thyroid cells.

The three dimensional distribution of chromium and nickel alloy welding fumes.

In the present study, the fumes generated from manual metal arc (MMA) and submerged metal arc (SMA) welding of low temperature service steel, and the chromium and nickel percentages in these fumes, were measured at various horizontal distances and vertical heights from the arc in order to obtain a three dimensional distribution. The MMA welding fume concentrations were significantly higher than the SMA welding fume concentrations. The highest fume concentration on the horizontal was shown in the fumes collected directly above the arc. The fume concentration vertically was highest at 50 cm height and reduced by half at 150 cm height. The fume concentration at 250 cm height was scarcely different from that at 150 cm height. The distribution of the chromium concentration vertically was analogous to the fume concentration, and a statistically significant difference in the chromium percentages was not found at the different heights. The nickel concentrations were not statistically significant within the welding processes, but the nickel percentages in the SMA welding fumes were statistically higher than in the MMA welding fumes. The highest nickel concentration on the horizontal was found in the fumes collected directly above the arc. The highest nickel concentration vertically showed in the fume samples collected at 50 cm height, but the greater the height the larger the nickel percentage in the fumes.

[Intra-individual and seasonal variations of thyroid function tests in healthy subjects].

We report intra-individual and seasonal variations of thyroid function tests in healthy subjects. Blood samples were obtained from thirteen healthy males and seven healthy females every two weeks over a period of one year, and totally 25 samplings of each were made. Serum thyrotropin (TSH), free thyroxine (FT4) and free triiodothyronine (FT3) were measured after the completion of the sampling. The 25 samples from each subject were always assayed with the same assay run. Variations of FT4 and FT3 in each subject were narrow and approximately one-third of normal reference ranges. The magnitude of individual variation of TSH values was proportional to the average of TSH in each individual. Serum TSH and FT3 values during winter were significantly higher than those during summer, but such change was not observed on serum FT4.

[Effect of theophylline on the thyroid function in healthy subjects: comparison between the short- and long-term medication].

Effect of theophylline on the thyroid function was studied in 9 healthy subjects. Theophylline (200mg) was taken two times (AM8:00, PM10:00) and blood was collected two times (AM9:00, PM4:00) a day for five days. Five of these 9 subjects took same dose two times (AM8:00, PM10:00) a day and blood was collected once (AM9:00) a week for four weeks. In short-term medication, serum free thyroxine (FT4) increased significantly (1.19 +/- 0.19 ng/dl, before medication) in 4th day AM (1.29 +/- 0.14 ng/dl, p < 0.05), in 4th day PM (1.30 +/- 0.12 ng/dl, p < 0.05) and in 5th day AM (1.30 +/- 0.16 ng/dl, p < 0.05). Serum free triiodothyronine (FT3) increased significantly (3.9 +/- 0.36 pg/ml, before medication) in 4th day AM (4.3 +/- 0.66 pg/ml, p < 0.05) and in 5th day AM (4.3 +/- 0.61 pg/ml, p < 0.05). Serum thyroid stimulating activity (TSA), which was measured as an increase in cAMP in FRTL-5 cells, increased significantly (116.5 +/- 49.5%, before medication) in 1st day PM (152.3 +/- 60.0%, p < 0.05), in 2nd day PM (192.6 +/- 86.7%, p < 0.05), in 3rd day PM (208.5 +/- 94.1%, p < 0.05) and in 4th day AM (183.5 +/- 80.1%, p < 0.05). In contrast, serum FT4, FT3, TSH, and TSA did not increase significantly in long-term medication.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of various sampling condition on the measurement of circulating TSH and free thyroxine].

We report here the effect of various sampling and storage condition on the measurement of circulating TSH and free thyroxine (FT4). Blood samples were obtained from five normal subjects using four kinds of sampling tubes; plane glass tube, glass tube containing serum separator, and glass tube containing EDTA-2Na or heparin-sodium. We stored whole blood, serum or plasma at low temperature (4-8 degrees C) or at room temperature (20-25 degrees C) from one hour to thirteen days. Both values of EDTA-plasma TSH and FT4 were significantly lower than those of serum samples, EDTA-plasma TSH value was increased gradually during storage at room temperature but not at low temperature. Serum or plasma FT4 values were decreased during storage at room temperature but not at low temperature. In conclusion, circulating TSH and FT4 values are influenced by different sampling tubes and, serum or plasma TSH and FT4 are not always stable under the storage condition at room temperature. Serum samples obtained by using plane glass tube and kept at low temperature give us more reliable values of TSH and FT4.

[Serum TSH measurement].

Serum TSH (thyrotropin) measurement is the first-line test to evaluate the thyroid function. Recent sensitive serum TSH assays are based on immunometric assays (IMAs) that use two or more antibodies. Electrochemiluminescent immunoassay expanded both the functional sensitivity potential and the range of serum TSH measurement. It is usually combined with serum free T4 measurement to evaluate the thyroid function, but can be used alone when the pituitary function is normal. Serum TSH levels do not reflect the thyroid function, i) when thyroid function is changing widely, ii) in low T4-T3 states, iii) in central hyperthyroidism or hypothyroidism, and iv) when antibodies such as heterophile antibodies, rheumatoid factors, and rarely anti-TSH antibodies are present.