Serum Ratio of Triiodothyronine to Thyroxine, and Thyroxine-Binding Globulin and Calcitonin Concentrations in Graves' Disease and Destruction- Induced Thyrotoxicosis*

Abstract

The serum ratios of T3 to T4, and T4-binding globulin (TBG) and calcitonin concentrations were studied in cases of thyrotoxic Graves' disease and destruction-induced thyrotoxicosis. In 272 patients with Graves' disease, 209 of 240 (87%) untreated patients without complications had high T3 to T4 ratios (nanograms per micrograms) of more than 20. Six of 32 (19%) patients with Graves' disease who had complications (15 with pregnancy, 14 with increased TBG, and 3 with conditions associated with a low T3 syndrome) had high T3 to T4 ratios. Eleven of 74 (15%) patients with destruction-induced thyrotoxicosis (24 with subacute thyroiditis, 39 with postpartum transient thyrotoxicosis, and 11 with spontaneous transient thyrotoxicosis) had high T3 to T4 ratios. Patients who had serum T4 levels of more than 30 micrograms/dl and/or T3 levels of more than 800 ng/dl had Graves' disease. There was no significant correlation between the T3 to T4 ratio and activities of thyroid-stimulating immunoglobulins in thyrotoxic patients with Graves' disease who had no complications. The average serum levels of TBG in destruction-induced thyrotoxicosis and thyrotoxic Graves' disease were 20.7 +/- 4.3 micrograms/ml (mean +/- SD; n = 22), and 19.9 +/- 4.0 (n = 41), respectively, which were significantly lower than that in healthy subjects (22.7 +/- 4.4 micrograms/ml; n = 165), but there was no difference between the values in the two groups of thyrotoxicosis patients. The average serum level of calcitonin in destruction-induced thyrotoxicosis patients was 96.7 +/- 66.7 pg/ml (n = 21), which was significantly (P less than 0.05) higher than the values in patients with thyrotoxic Graves' disease (62.0 +/- 44.7 pg/ml; n = 26) and in healthy subjects (63.9 +/- 31.2 pg/ml; n = 29), but the difference in values in the two groups of thyrotoxicosis was not clinically useful because of considerable overlap of individual values. The T3 to T4 ratio is a simple and helpful index for the differentiation of the two types of thyrotoxicosis. A T3 to T4 ratio less than 20 in thyrotoxic patients before therapy is a laboratory signal of destruction-induced thyrotoxicosis or Graves' disease with complications, but final differentiation should be confirmed by measuring radioactive iodine uptake.

Determinants of serum T4 and T3 at the time of diagnosis in nosological types of thyrotoxicosis: a population-based study

“…On the other hand, we found no association between iodine intake from vitamin supplements and the degree of biochemical thyrotoxicosis at disease onset. Finally, TRAb-negative GD patients had mild thyrotoxicosis, which is in accordance with most (34,35,36) but not all studies (5). Based on our findings, two extremes of GD patients were identified: a group of women aged !40 years living in Copenhagen with only mild iodine deficiency and having measurable TRAb (high T 3 group), and at the other end of the spectrum a group of TRAb-negative patients aged R40 years who lived in and around Aalborg with moderate iodine-deficiency (low T 3 group).…”

“…In addition, we found that GD patients had higher T 3 and T 4 levels compared with MNTG but not among those aged 80C years. It must be emphasized that there is a considerable overlap in serum T 3 and T 4 in the different subtypes both in this and in other studies (5,25,29). However, a serum T 3 R5.0 mmol/l (approximately twice the upper reference limit) was nearly only seen in patients with GD, where 52.6% had such severe abnormality compared with only 4.0/5.2% of patients newly diagnosed with MNTG/STA.…”

“…Thus, determinants for levels of serum T 3 and T 4 have not been studied in detail even if previous studies reported on various details such as influence of age (2,3), sex (3), iodine intake (4), and TSH receptor antibody (TRAb) concentration (5,6). Limited patient characteristics were included in most of these studies, and often they did not take various possible confounders into account, such as smoking, known to aggravate iodine deficiency (7) and to modulate thyroid autoimmunity (8), alcohol intake that besides from influencing the risk of Graves' disease (GD) (9) also may supply flavonoids known to modulate the selenodeiodinase activity (10), intake of vitamin supplements often containing iodine, and co-morbidity.…”

Iodine status, thyroid function and pregnancy: study of Swedish and Sudanese women

“…Human chorionic gonadotrophin (HCG) produced by the placenta has a weak thyroid stimulatory effect and the rapid rise in HCG in early pregnancy is often accompanied by some alterations in serum thyroid hormone and thyrotropin (TSH) levels (Braunstein & Herhman, 1976;Yoshkawa et al, 1989;Pekonen et al, 1988). Also, the marked increase in the synthesis of thyroxine-binding globulin resulting from the increasing oestrogen levels affects the thyroid hormone homeostasis by expanding the thyroid hormone binding compartment (Glinoer et al, 1990;Ericsson & Threll, 1986;Amino et al, 1981). Further the extra need of iodine imposed by pregnancy can serve to unmask a mild iodine de®ciency as re¯ected in a relative hypothyroxinaemia and increasing maternal TSH levels (Glinoer et al, 1990).…”

Superior thyroid artery mean peak systolic velocity for the diagnosis of thyrotoxicosis in Japanese patients

“…Superior thyroid artery mean peak systolic velocity for the diagnosis of thyrotoxicosis in Japanese patients Toyoyoshi Uchida 1) , Kageumi Takeno 1) , Masahiro Goto 1) , Rei Kanno 1) , Sayaka Kubo 1) , Satomi Takahashi 1) , Kousuke Azuma 1) , Ken Sakai 1) , Yoshio Fujitani 1), 2) , Takahisa Hirose 1), 2) , Ryuzo Kawamori 1), 2), 3) and Hirotaka Watada 1) ultrasonography (EUB-525, Hitachi, Tokyo) with a 10-MHz linear transducer. Thyroid volume was calculated using the ellipsoid model ((width x length x thickness x π/3) for each lobe + (width x length x thickness) for isthmus).…”