Measurements of antithyroglobulin and antimicrosomal (antiperoxidase) antibodies have been performed widely for the clinical diagnosis of autoimmune thyroid diseases. The present study was designed to compare these antibody titers with histological findings of the thyroid in patients with diffuse goiter who were suspected of having Hashimoto's thyroiditis. One hundred and ten euthyroid or hypothyroid patients (10 males and 100 females; age 48 +/- 15 (SD) years old) with diffuse goiter were studied for the measurement of antithyroglobulin and antimicrosomal or antiperoxidase antibodies by a hemagglutination technique (TGHA and MCHA, respectively) and by a newly developed radioassay (TgAb and TPOAb, respectively). The antibody titers were compared with the histological findings obtained by needle biopsy. TgAb, TPOAb, TGHA, and MCHA were detected in 80 (96.4%), 61 (73.5%), 37 (44.6%), and 54 (65.1%) of 83 patients with histologically proven Hashimoto's thyroiditis, respectively, but in only one (3.7%) of 27 patients without any inflammatory changes in the biopsy specimen. In 55 patients with negative TGHA and MCHA, the TgAb positivity was more closely associated with the histological diagnosis of Hashimoto's thyroiditis than the TPOAb positivity was, the incidence of each antibody in Hashimoto's thyroiditis being 89.7% (26/29) and 27.6% (8/29), respectively. In conclusion, the histological diagnosis of Hashimoto's thyroiditis can most precisely be predicted by the newly developed radioassay for TgAb.

To evaluate the temporal features of physiological fluctuation in serum PTH concentration, we sampled peripheral blood at 4-min intervals for 24 h from five normal men (32.8 yr; range, 26-40 yr) and measured serum PTH levels using a two-site immunoradiometric assay with the exquisite sensitivity and specificity for human PTH-(1-84) (intact PTH). The resultant 24-h time series of serum intact PTH levels were assessed by contemporary techniques in chronophysiology for rhythmic and episodic peak detection. Cosinor analysis disclosed a significant circadian rhythm in serum intact PTH concentrations in all five men, with the mean circadian amplitude and acrophase of 7.2 +/- 4.4 ng/L and 2305 +/- 401 h, respectively (mean +/- SD; n = 5). No apparent fixed ultradian periodicity was found by autocorrelation and spectral analyses. Evaluation of episodic intact PTH pulsatility by Cluster analysis revealed 23.0 +/- 4.4 discrete PTH pulses/24 h (P less than 0.01 vs. signal-free noise), which occurred at an interpulse interval of 61.6 +/- 11.1 min. The average duration of a serum intact PTH peak was 42.8 +/- 7.3 min, and its mean incremental amplitude was 12.6 +/- 1.3 ng/L, which corresponded to a 31.8 +/- 5.2% increase above the preceding nadir. Discrete PTH peaks were separated by nonpulsatile valleys which lasted for 17.9 +/- 4.4 min. Cross-correlation between the time series of serum intact PTH and whole blood ionized calcium (Ca2+) was at its maximum (-0.5) at concurrent time points in three subjects, while significant positive correlation between serum intact PTH and simultaneous serum inorganic phosphorus concentrations was observed in four of five subjects. There was no apparent correlation between the levels of serum intact PTH and serum magnesium. Our data show that serum levels of intact PTH, the only biologically active form of PTH in the blood, is characterized by a significant circadian periodicity, spontaneous episodic pulsatility with distinct peak properties, and a significant temporal coupling with Ca2+ and inorganic phosphorus concentrations. We conclude that PTH secretion, as judged by the temporal pattern of serum intact PTH levels, is pulsatile in normal men.

The third-generation TSH assay is useful for the differential diagnosis of various types of thyrotoxicosis, especially between Graves' disease and destructive thyroiditis.

In order to elucidate causes of subclinical thyrotoxicosis, we reviewed records of thyroid function tests obtained in our hospital between 1990 and 1992 showing normal thyroid hormones and subnormal TSH levels, and analyzed underlying clinical conditions of the patients. Of 186 patients with normal T4 and/or free T4 and normal T3 and/or free T3 but subnormal TSH (< 0.1 mU/l) levels in serum, 150 were under treatment with antithyroid drugs for hyperthyroid Graves' disease or with thyroid hormones for hypothyroidism. Twelve were in remission after treatment for Graves' disease, and 4 had destructive thyroiditis. Of the remaining 20 patients, 4 had autonomously functioning thyroid nodule (AFTN), 9 had euthyroid ophthalmic Graves' disease (EOG), and 7 had diffuse goiter without apparent ophthalmopathy (DG). When thyroid stimulating antibodies (TSAb) were measured in the last 3 groups of the patients, they were detected in none with AFTN but in all patients with EOG and DG. These 7 DG patients without ophthalmopathy had a clinical feature showing unstable thyroid functions, changeable to euthyroidism, overt hyperthyroidism and even hypothyroidism during follow-up. In conclusion, TSAb measurement is useful for detection of subclinical Graves' disease in euthyroid subjects with subnormal TSH levels in serum.