Kinetic Study of Immunoreactive Human Thyroglobulin

Abstract

Thyroglobulin (Tg) can be detected in the circulation of normal subjects. Serum Tg is increased in patients with various thyroidal disorders including Graves' disease; however, little is known about Tg metabolism. Therefore, a kinetic study of human Tg was carried out in 13 normal men, 19-28 yr old, and 6 untreated hyperthyroid patients with Graves' disease, 3 men (22 to 25 yr old), and 3 women (21 to 63 yr old). Ten milligrams of Tg were injected as a bolus dose. Blood samples were collected before and 10 min, and 2, 4, 6, 8, 12 h and every 12 h up to 72 h after injection. Concentrations of serum Tg were measured by an RIA method developed in our laboratory. Anti-Tg antibody was not detected in any subject. Various indices of this kinetic study were calculated using single compartmental analysis. In 13 normal subjects, the mean serum concentrations of Tg were 17 +/- 12.6 (SD) ng/ml; mean half-life was 29.6 +/- 2.8 h; distribution volume was 11,210 +/- 3,076 ml/60 kg body weight; fractional decay was 2.40 +/- 0.22%/h; MCR was 268.9 +/- 87.8 ml/h X 60 kg; and release rate was 100.3 +/- 50.2 micrograms/day X 60 kg. Serum concentrations of Tg were increased in four of the six untreated hyperthyroid patients with Graves' disease. Their Tg half-lives and MCR were within the normal range. In the two patients who had normal serum concentrations of Tg, the Tg half-lives were shorter and MCR were greater than in normal subjects. The release rates of Tg were increased in all six of these patients. In summary, in hyperthyroid patients, Tg release is significantly greater than normal, whereas Tg metabolism is similar to that in normal subjects.

Early Sequential Changes in Serum Thyroglobulin After Radioiodine Ablation for Thyroid Cancer: Possible Clinical Implications for Recombinant Human Thyrotropin-Aided Therapy

“…We also find an intersubject variability in Tg kinetics and Tg levels. This could be related to many factors, including variations in residual thyroid volume, avidity for radioiodine, cell sensitivity to ionizing radiation, or Tg metabolism (9). In the present study, Tg values were positively correlated to normalized count ratio ROI 80 and ROI 80 /ROI surface.…”

Identification of thyroid hormone residues on serum thyroglobulin: a clue to the source of circulating thyroglobulin in thyroid diseases

“…Tg production by metastases was also extremely high. Using metabolic parameters of serum Tg determined by Lo Gerfo et al (21) in patients with DTC, one can estimate that the maintenance of serum Tg at a value of 30 mg/ml (serum Tg concentration of patient DTC 89) would require a daily production of about 165 mg. By comparison, the amount of Tg synthesized per day by a normal thyroid gland is about 30 mg (22). The high serum T4 and serum Tg concentrations were related to the existence of large tumor masses with differentiated thyroid activities.…”

Interleukin-1 inhibits thyrotrophin-induced human thyroglobulin gene expression

“…The probes used in this study were labelled with 32P-aCTP by random prime labelling to a specific activity of 5-10 l01c.p.m./pgDNA. Tg concentration measurements Concentrations of Tg in medium were measured by a radioimmunoassay originally established in our laboratories (Izumi & Larsen, 1977;Izumi, Kubo, Taura et al 1986). …”