Influence of Frequency of Previous Pregnancies on the Prevalence of Thyroid Nodules in Women Without Clinical Evidence of Thyroid Disease

Abstract

In a region with insufficient alimentary iodine supply (Kiel, Northern Germany) the prevalence of thyroid nodules was studied by means of ultrasonography in 212 healthy women (36-50 years old) in four groups of 53 women each with 0, 1, 2, and 3-5 previous pregnancies. Goiters were found in 28.3% (15 of 53) of the women without children and in 28.9% (46 of 159) of the women with children. There was no significant increase of goiter prevalence according to the number of pregnancies. We detected thyroid nodules in 21.2% (45 of 212). Only 9.4% (5 of 53) of the women without previous pregnancies had thyroid nodules, but 25.1% (40 of 159) of the women with pregnancies in the past had nodules, the difference being statistically significant (p < 0.05). We observed nodules in 11 of 53 women with 1 child (20.7%), in 11 of 53 women with 2 children (20.7%), and in 18 of 53 women with 3-5 previous pregnancies (33.9%). We propose that, in regions with borderline or insufficient alimentary iodine supply, accentuated iodine deficiency during pregnancies due to increase of iodine requirement is a probable cause for the higher prevalence of thyroid nodules in women with previous pregnancies.

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

“…The prevalence of thyroid nodules varied between 3% and 21% (183,217,218) and increased with increasing parity (9.4% without a prior pregnancy, 20.7% with one prior pregnancy, 20.7% with two prior pregnancies, and 33.9% with three or more prior pregnancies) (217). In the Belgian study, 60% of the nodules doubled in size during pregnancy yet remained between 5 and 12 mm (183).…”

Thyroid Nodules

“…4 The gender disparity is perhaps explained by the hormonal influences of both estrogen and progesterone, as increasing nodule size and new nodule development have been demonstrated to be related to pregnancy and multiparity. 9,10 Exposure to ionizing radiation, either during childhood, or as an occupational exposure, will cause a rate of development of thyroid nodules of 2% per year, reaching a peak incidence in 15 to 25 years. 11,12 …”

Acute Increase in Goiter Size During a Normal Pregnancy: An Exceptional Case Report

“…In 1991, a prospective cohort study of euthyroid women with mild thyroidal abnormalities showed that in those women who had preexisting nodules there was frequently an increase in nodule size, and the formation of new nodules in 20% of cases during gestation (6). In 1993, a retrospective study showed a 9% prevalence of thyroid nodularity in nulliparous women, while the prevalence was significantly increased to 25% in women who had previously been pregnant (15). Recently in an area with iodine sufficiency, Kung et al (16) showed that 4% of women had palpable nodules and 15% micronodules identified by ultrasound in the first trimester of pregnancy.…”