Background: Thyroid disease in pregnancy is common with hypothyroidism predominating.
Objectives: To determine the aetiology of thyroid disease in patients attending an antenatal thyroid clinic, their baseline biochemical and therapeutic characteristics as well as subsequent management.
Subjects/setting: 114 women with a mean 31 years (±5) age were seen by a consultant endocrinologist in the antenatal thyroid clinic, between September 2013 and November 2014.
Methods: A retrospective audit of case notes and electronic records of patients identified from clinic lists.
Results: Median gestation at initial review was 16 weeks (IQR 1320). Diagnoses included hypothyroidism (84%), gestational thyrotoxicosis (6%), Graves (6%), and other (4%). 89% of patients had previous episodes/persisting thyroid disease pre-pregnancy with a mean duration of 5 years (IQR 2.48.0). The remaining 11% presented with new thyroid disease during pregnancy with the majority having gestational thyrotoxicosis or positive thyroid TPO antibodies but normal thyroid function. No new cases of Graves disease were diagnosed during pregnancy. For patients with hypothyroidism median dose of levothyroxine (L-T4) at initial consultation was 100 μg/day (IQR 50144). Based on initial and then subsequent blood tests (between 5 and 7 weeks after each appointment), 44% did not require any dose adjustment (TSH 1.9 mU/l±1.9), whilst 37% had one (TSH 5.4 mU/l±6.8), 13% had two (8.2 mU/l±6.1), 5% had three (4.0 mU/l±0.22), and one patient had four dose adjustments (TSH <0.01 mU/l). Note that the mean±S.D. for TSH is quoted at the time dose adjustment was deemed necessary. On final follow up FT4 had normalised in all hypothyroid patients and only one patient had mild elevation of TSH (TSH=7.2).
Conclusions: Current recommendations suggest a 3050% increase in T4 for all patients at initial consultation. Our data suggest that this is not necessary for almost half of patients with pre-existing hypothyroidism and in those that do require an increase, the average required is 41 μg (±19).