Materials and methods
thyroid dysfunction, hypothyroidism
THYROID DYSFUNCTION, HYPOTHYROIDISM, HYPERTHYROIDISM, RECRUITMENT
Participants were the offspring of the Safety and Efficacy of Lipiodol in Fertility Investigations (SELFI) study, conducted in Auckland. The study was approved by the Northern B Health and Disability Ethics Committee (Ministry of Health; 19/NTB/52) and registered with the Australian New Zealand Clinical Trials Registry (ANZCTR: 12620000738921). The aim of the SELFI study was to assess the magnitude and pattern of iodine excess and thyroid dysfunction following an OSCM HSG. The SELFI study cohort consisted of 196 consecutive consenting women who underwent OSCM HSG from July 2019 to April 2021, without overt hypothyroidism or hyperthyroidism, and who had not undergone recent hysterosalpingography. Participants had baseline assessments of urine iodine concentrations (UIC), TSH, FT4, and free triiodothyronine (FT3), and serial measurements of the same parameters for six months. More details on recruitment and assessments can be found in the published protocol (Flow diagram for the SELFI Study including the women who underwent oil-soluble contrast medium (OSCM) hysterosalpingography (HSG), those who became pregnant, and the subsequent number of newborns included in this study. Dashed black line indicates the newborns whose parents declined the Day 7 thyroid function test.All 57 babies had whole-blood TSH levels tested (from Guthrie cards) under New Zealand’s Newborn Metabolic Screening Programme 48 hours after birth. In addition, day 7 thyroid function tests were performed on newborns whose parents provided written informed consent for heel-prick sampling. The latter provided serum samples for thyroid function tests measuring concentrations of TSH, FT4, and FT3. No physical examinations were performed on these neonates, but data on sex, gestational age, birth anthropometry (weight, length, and head circumference), ethnicity, and mode of delivery were obtained from hospital records. Ethnicity of the newborn was reported by the parents, with a single ethnicity ascribed using the established hierarchical classification (First-morning urine samples were used in mothers to measure UIC by inductively coupled plasma mass spectrometry (ICP-MS) using Agilent 7700 [coefficient of variation (CV) of 10.8%]. The assay for the newborn screening TSH was the GSP™ Neonatal hTSH (CV-8%). Serum TSH, FT4, and FT3 concentrations were measured with an electrochemiluminescence immunoassay using an ADVIA Centaur XP analyzer (Siemens Healthcare Diagnostics Inc., Tarrytown, NY, USA), with CVs ≤5% (