Helen Marx registrar in obstetrics and gynaecology , Pina Amin consultant obstetrician , John H Lazarus professor of clinical endocrinology, and honorary consultant physician
Marx H, Amin P, Lazarus J H.
Hyperthyroidism and pregnancy
BMJ 2008; 336 :663
doi:10.1136/bmj.39462.709005.AE
Consider glucocorticoids for severe thyrotoxicosis due to Graves disease in pregnancy
Marx et al correctly state that pregnancies in untreated or poorly controlled thyrotoxic women are more likely to be complicated by pre- eclampsia, heart failure, fetal loss, premature labour and having a low birthweight baby. Rarely thyroid storm may be precipitated by labor, infection, preeclampsia or cesarean section. In addition severe thyrotoxicosis due to Grave's disease may be complicated by pulmonary hypertension, a condition associated with significant maternal mortality in pregnancy.
As stated by Marx et al there is a delay in improvement in thyroid function with thionamides due to these medications only affecting the second and third of the four steps in thyroid hormone synthesis and release.
Where severe thyrotoxicosis occurs in pregnancy, especially around the time of partuition, glucocorticoids should be considered as adjunctive therapy for more rapid improvement in thyroid function while awaiting the effect of thionamides. Glucocorticoids are not foetotoxic or teratogenic. A two week course of prednisone in a dose of 25-50 mg / day can result in rapid clinical and biochemical improvement in thyrotoxicosis.
The mechanism of action of glucocorticoids in thyrotoxicosis due to Grave's disease is uncertain. The rapidity of response is more rapid than could be expected by the mechanism of inhibition of conversion of free thyroxine to tri-iodothyronine alone, and previous studies and my own experience is that levels of thyrotropin receptor stimulating antibodies do not change with glucocorticoid therapy.
Competing interests: None declared
Competing interests: No competing interests