The SELFI Study: Iodine Excess and Thyroid Dysfunction in Women Undergoing Oil-Soluble Contrast Hysterosalpingography

• Published in: The journal of clinical endocrinology and metabolism 2022-12, Vol.107 (12), p.3252-3260
• Main Authors: Mathews, Divya M, Peart, Jane M, Sim, Robert G, Johnson, Neil P, O'Sullivan, Susannah, Derraik, Jose G.B, Hofman, Paul L
• Format: Article
• Language: English
• Subjects: Clinical; Hypothyroidism; Pregnancy; Thyroid gland; Thyrotropin; Thyroxine; Women
• ISSN: 0021-972X; 1945-7197
• DOI: 10.1210/clinem/dgac546

Context: Hysterosalpingography (HSG) with oil-soluble contrast medium (OSCM) improves pregnancy rates. However, OSCM has high iodine content and long half-life, leading to potential iodine excess. Objective: This work aimed to determine the pattern of iodine excess after OSCM HSG and the effect on thyroid function. Methods: A prospective cohort study was conducted of 196 consecutive consenting eligible women without overt hypothyroidism or hyperthyroidism. All completed the study with compliance greater than 95%. Participants underwent OSCM HSG (Auckland, 2019-2021) with serial monitoring of thyrotropin (TSH), free thyroxine (FT4), and urine iodine concentration (UIC) for 24 weeks. The main outcome measure was the development of subclinical hypothyroidism (SCH), defined as a nonpregnant TSH greater than 4 mIU/L with normal FT4 (11-22 pmol/L) in those with normal baseline thyroid function. Results: Iodine excess (UIC [greater than or equal to] 300 [mu]g/L) was almost universal (98%) with UIC peaking usually by 4 weeks. There was marked iodine excess, with 90% and 17% of participants having UIC greater than or equal to 1000 [mu]g/L and greater than 10 000 [mu]g/L, respectively. Iodine excess was prolonged with 67% having a UIC greater than or equal to 1000 [mu]g/L for at least 3 months. SCH developed in 38%; the majority (96%) were mild (TSH 4-10 mIU/L) and most developed SCH by week 4 (75%). Three participants met the current treatment guidelines (TSH > 10 mIU/L). Thyroxine treatment of mild SCH tended to improve pregnancy success (P= .063). Hyperthyroidism (TSH < 0.3 mIU/L) occurred in 9 participants (5%). Conclusion: OSCM HSG resulted in marked and prolonged iodine excess. SCH occurred frequently with late-onset hyperthyroidism occasionally. Regular thyroid function tests are required for 6 months following this procedure. Key Words: iodine, hysterosalpingography, oil-soluble contrast, thyroid, pregnancy Abbreviations: aRR, adjusted relative risk; ATA, American Thyroid Association; FT3, free 3,5,3'-triiodothyronine; FT4, free thyroxine; HSG, hysterosalpingography; OSCM, oil-soluble contrast medium; SCH, subclinical hypothyroidism; SELFI, Safety and Efficacy of Lipiodol in Fertility Investigations; TPO, thyroid peroxidase; TSH, thyrotropin; TwAUC, time-weighted area under the curve; UIC, urine iodine concentration; WSCM, water-soluble contrast medium.