Oral Presentation ESA-SRB-APEG-NZSE 2022

Iodine excess and thyroid dysfunction in women undergoing oil-soluble contrast hysterosalpingography (#191)

Divya Mathews 1 , Jane Paert 2 , Robert Sim 2 , Neil Johnson 3 , Susannah O'Sullivan 4 , José Derraik 1 , Paul Hofman 1
  1. Liggins Institute, Auckland, NEW ZEALAND
  2. Auckland Radiology Group, Auckland, NEW ZEALAND
  3. Repromed Fertility, Auckland, NEW ZEALAND
  4. Endocrinology, Greenlane clinical centre, Auckland, NEW ZEALAND

Hysterosalpingography with oil-soluble contrast medium (OSCM) improves pregnancy rates1. However, OSCM has high iodine content and long half-life, leading to potential iodine excess2,3. The aim was to determine the pattern of iodine excess after OSCM hysterosalpingography and the impact on thyroid function.
For this, a prospective cohort study was conducted on 196 consecutive consenting eligible women who underwent OSCM hysterosalpingography in Auckland, NewZealand (2019-2021)4. Participants underwent hysterosalpingography with OSCM followed by serial monitoring of thyroid stimulating hormone (TSH), free thyroxine (FT4) and urine iodine concentration (UIC) for 24 weeks (compliance>95%). A delayed pelvic X-ray was taken 45 minutes after hysterosalpingography and OSCM retention was graded by the radiologist. The primary outcome was development of subclinical hypothyroidism (SCH), defined as a non-pregnant TSH >4 mIU/L with normal FT4 (11–22 pmol/L), in those with normal baseline thyroid function.
Iodine excess (UIC ≥300 μg/L) was almost universal (98%) among the participants, with UIC peaking usually by four weeks. There was marked iodine excess, with 90% and 17% of participants having UIC ≥1000 μg/L and >10,000 μg/L, respectively. Iodine excess was prolonged with 67% having a UIC ≥1000 μg/L for at least three months. OSCM retention grading was associated with the magnitude of iodine excess (p<0.001). 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=0.046]. Hyperthyroidism (TSH <0.3 mIU/L) occurred in 9 participants (5%). A higher baseline TSH or lower baseline iodine levels were associated with an increased risk of developing SCH.
OSCM hysterosalpingography 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.