[A radioimmunoassay for the measurement of thyroglobulin in human serum and its application to clinical study (author's transl)]

The differential diagnosis of cystic neck masses by the determination of thyroglobulin concentrations in the aspirates

Thyroglobulin (Tg) concentrations in the aspirates of various types of cystic neck masses were measured by RIA to assess the usefulness of this determination in differential diagnosis. The subjects consisted of 16 patients, whose final diagnoses were all established on the basis of operative results; three patients had follicular thyroid adenomas (F-Ad), 11 had papillary thyroid carcinomas (P-Ca), one had a thyroglossal duct cyst (TDC) and one had a lateral cervical cyst (LCC). Tg concentrations in the cyst fluids of F-Ad and P-Ca were very high (0.042-2.83 mg/ml) compared with serum Tg concentrations. There was no difference in Tg concentrations in the fluids of P-Ca between primary lesions (n = 5) and metastatic lesions (n = 6). On the other hand, Tg concentrations of TDC and LCC were very low (less than 100 ng/ml). Difficulty was experienced in diagnosing three patients, even though they had been examined by all nonsurgical diagnostic techniques. However, an occult thyroid carcinoma with lymph node metastasis was diagnosed by demonstrating a high Tg concentration in the aspirate of the cystic lymph node. T3 concentrations in cyst fluids of F-Ad were higher than those of P-Ca. T3 concentrations in the fluids of P-Ca, TDC and LCC did not differ, and were similar to serum T3 levels. Cytology of cyst fluids was positive in four of 10 patients examined with P-Ca. In conclusion, we can clearly confirm the thyroid origin of a cystic neck mass by demonstrating a high Tg concentration in the aspirate. This is especially useful for diagnosis in patients with thyroid carcinoma, including occult thyroid carcinomas with cystic lymph node metastasis.

Elevated serum thyroglobulin as a manifestation of acute haemorrhage into the thyroid gland

Clinical observations and serial determinations of serum thyroglobulin (Tg) were made in five patients with acute haemorrhage into the thyroid gland. Fever, local pain and acceleration of erythrocyte sedimentation rate were minimal or were not observed, and serum T4 and T3 were normal. Although all patients showed an increase in serum Tg, this was most obvious in three subjects and it gradually decreased as the nodule became smaller. There was no correlation between the serum Tg concentration and the nodular size. Acute haemorrhage into the thyroid gland should be added as one of the causes to increase serum Tg concentrations.

An enzyme immunoassay for the measurement of thyroglobulin in human serum

An enzyme-linked sandwich immunoassay using silicone rods coated with rabbit (anti-human thyroglobulin) immunoglobulin G and rabbit (anti-human thyroglobulin) monovalent fragment of immunoglobulin F (Fab') conjugated with beta-D-galactosidase was developed for the measurement of thyroglobulin in human serum. The volume of serum needed for the assay was as little as 2 microliters. The sensitivity of the assay was 3.5 ng/ml, which is equal to or rather higher than that of radioimmunoassay. The specificity of the assay was demonstrated by the following observations: (1) The absence of crossreaction of thyroxine and triiodothyronine, (2) non-detectability of thyroglobulin in the sera of patients who underwent total thyroidectomy, (3) parallelism of the standard curve with dilutions of reference serum. The precision of the assay was proven by the demonstration of the sufficient recovery of human thyroglobulin added to sera (92--99%) and coefficients of variance in within and between assays were 6.2--9.3 and 2.5--5.3%, respectively. Furthermore, a highly significant correlation was observed between thyroglobulin concentrations measured by our enzyme immunoassay and those by radioimmunoassay (r = 0.99, p less than 0.001, n = 63). Human thyroglobulin in serum was detectable in 90% of 146 normal subjects, the concentration (mean +/- S.D.) being 13.3 +/- 10.3 ng/ml.