Radioimmunoassay for Measurement of Thyroglobulin in Human Serum

Abstract

A B S T R A C T A specific and reproducible double antibody radioimmunoassay for the measurement of thyroglobulin (HTg) in human serum has been developed. Since antithyroglobulin autoantibodies combine with the ["3'I] HTg tracer, antibody-positive sera were rejected for measurement. Specificity is demonstrated in that thyroid analogous such as thyroxine (T4), triiodothyronine (T3) monoiodotyrosine (MIT) and diiodotyrosine (DIT) did not crossreact. Sera previously reacted with anti-HTg-Sepharose contained no immunoassayable HTg. Finally, sera obtained from patients after total thyroid ablation for thyroid carcinoma did not contain demonstrable HTg. The sensitivity of the assay is 1.6 ng/ml, and HTg was detectable in 74% of 95 normal subjects. The mean concentration was 5.1 ng/ml ±0.49 SEM (range < 1.6-20.7 ng/ml). Day to day variation in HTg levels is large in some euthyroid subjects and nearly absent in others. HTg was detectable in 90% of the sera obtained in 23 pregnant women at delivery in whom a mean concentration of 10.1 ng/ml ±1.3 SEM was observed. The mean level for the corresponding newborn infants at birth was 29.3 ng/ml ±4.7 SEM a value significantly higher than the mean maternal HTg concentration (P < 0.001). A group of 17 thyrotoxic individuals all had elevated HTg levels; the mean for this group was 344.8 ng/ml ±90.7 SEM. In the acute phase of subacute thyroiditis HTg was also elevated in all of 12 patients, and the mean for this group was 136.8 ng/ml ±74.6 SEM.

Serum thyroglobulin (Tg) concentration in healthy subjects: Absence of age- and sex-related differences.

“…Concerning the sex differences in serum Tg values, some workers (Van Herle et al, 1973 ;Pezzino et al, 1977 ;Pacini et al, 1980) reported significantly higher values in healthy females than in healthy males. Other workers, however, did not find significant difference (Roitt and Torrigiani, 1967 ;Torrigiani et al, 1969 ;Ochi et al, 1975 ;Gardner et al, 1979).…”

“…Several previous studies (Van Herle et al, 1973 ;Izumi and Larsen, 1978 ;Gardner et al, 1979;Pacini et al, 1980) have demonstrated varying degrees of elevated levels of serum Tg in thyroid diseases such as Graves' disease and subacute thyroiditis. In patients with thyroid carcinoma, Tg is a useful marker for their follow-up (Van Herle and Uller, 1975 ;Pacini et al, 1980), since the levels of serum Tg after thyroidectomy are low or undetectable in patients with complete remission, whereas elevated serum Tg indicates metastasis and/or recurrence of carcinoma.…”

Thyroglobulin as a Biomarker of Iodine Deficiency: A Review

“…Several of these early studies (48)(49)(50) reported that Tg was undetectable in some healthy participants. For example, a small study conducted by Hjort et al (48) used a RIA with a limit of detection (LoD) of 50 lg/L and found that Tg was undetected in all 12 healthy subjects, indicating that these subjects would likely have had Tg concentrations £50 lg/L.…”

Radioimmunoassay for Serum Thyroglobulin Designed for Early Detection of Metastases and Recurrencies in the Follow-Up of Patients with Differentiated Thyroid Carcinoma

“…According to van Herle et al (1) washing the precipitate is not necessary. This discrepancy may be due to the different assay volumes used.…”

“…Scveral methods have been published for the thyroglobuiin assay (1)(2)(3)(4). Radioimmunoassay has found wide application, and most assays employ the double antibody procedure.…”