Decreased serum thyroglobulin levels in the late stage of pregnancy

Abstract

Serum thyroglobulin levels were serially measured in 25 normal pregnant women to evaluate thyroidal activity during normal pregnancy. Measurements included serum T3, T4, free T4, TBG, and TSH.Tg and FT4 levels were found to be decreased in the third trimester when compared with those of the first trimester and with those of normal non-pregnant individuals (P < 0.01). TSH levels were higher than normal in pregnant women at all stages of pregnancy, with a significant rise at the third trimester. These findings suggest the presence of a subclinical hypothyroid state in the late stage of normal pregnancy.It has been reported that the levels of serum free thyroxine (FT4) and free 3,5,3'-triiodothyronine (FT3), measured by the classic equilibrium dialysis method (Sterling & Brenner 1966;Weeke et al. 1982) and the recent analog-type radioimmuno¬ assay (RIA, Franklyn et al. 1983a,b;Smith & Bold 1983), are decreased in the late stage of normal pregnancy. However, the clinical significance of these findings has not been clarified, since preg¬ nant women show none of the clinical features of hypothyroidism, and the results of these RIAs have been shown to be influenced by serum albu¬ min levels (Stockigt et al. 1982;Amino et al. 1983; Midgley & Wilkins 1983), which to some extent may change during pregnancy. It is thus import¬ ant to study other indexes of thyroid status which are not influenced by TBG or albumin. As serum thyroglobulin (Tg) levels have been reported to correlate with thyroid status , 1975Madeddu et al. 1984), we followed the serum Tg levels during normal pregnancy in order to see whether they would decrease with the FT4 levels or not. Materials and MethodsTwenty-live normal pregnant women with no previous history of thyroid diseases and no anti-thyroid anti¬ bodies in their sera were followed for the entire period of pregnancy. Blood was drawn at the first trimester (5-19 weeks), the second trimester (26-29 weeks), and the third trimester (35 -37 weeks). The sera were stored at -20°C.

Analytical and Clinical Evaluation of Three Sensitive Thyrotropin Assays

“…Although there still is some discussion about thyroid function during late pregnancy, we cannot confirm the observations of Hara et al 20 about the low TSH in pregnancy and we conclude in accordance with others8.21.22 that the TSH level is normal in late pregnancy and reflects the euthyroid state of these subjects.…”

Serum thyroglobulin during the menstrual cycle, during pregnancy, and post partum

“…These studies have all been characterized by the lack of a longitudinal design and adequate control groups. Hara and coworkers (8) investigated 25 women during pregnancy using a longitudinal de¬ sign and comparisons with non-pregnant agematched females and found a decrease in serum Tg level during pregnancy. In the latter study no post¬ partum follow-up was, however, included.…”

“…Pregnancy and the postparlum period involve substantial variations in thyroid function as well as thyroid size (2) although il is generally agreed lhat healthy women are euthyroid during this period. No sludies of serum Ihyroglobulin (Tg) during ihe menslrual cycle are available and pregnancy-re¬ lated alterations of serum Tg have been controver¬ sial (3)(4)(5)(6)(7)(8). In view of ihe increasing use of serum Tg in differenl thyroid disorders and in the follow-up of patients with differentiated thyroid carcinoma we have found it of inleresl to investigate the in¬ fluence of ihese physiologic factors on serum Tg in heallhy women.…”

Approach to the Pregnant Patient with Thyroid Cancer

“…In a study by Eltom et al (41), serum Tg, TSH, and urinary iodine concentrations were measured in 27 healthy pregnant Swedish women and in 21 Sudanese women. The median Tg levels in the pregnant Swedish women were 15.5 in the first, 10.5 in the second, and 18.0 g/liter in the third trimester.…”