RTH is a rare syndrome of reduced end organ sensitivity to circulating thyroid hormones . It is usually inherited in an autosomal dominant fashion with up to 85% of cases due to mutation in the thyroid hormone receptor β (THRβ) located in chromosome 3 [2,3]. RTH has a variable clinical phenotype where the patients can be euthyroid, hypothyroid, thyrotoxic or coexisting hypothyroid and thyrotoxic . Asymptomatic patients do not require treatment; otherwise, treatment options aiming to alleviate symptoms can be offered .
The implications of Thyroid hormone resistance (RTH) on pregnancy are not well understood, nor is there any evidence based guidelines available for the antenatal care of the kindred. Literature has suggested a 3- to 4- fold increase risk of miscarriage in female patients with RTH compared to the normal population. The risk is presumed higher if they carry an unaffected foetus . Unaffected infants born to affected mothers also had suppressed TSH at birth and a significantly lower birth weight than their affected siblings . These data indicate a direct toxic effect of thyroid hormone excess on the unaffected foetus.
We report a case of a young woman with known RTH who is currently pregnant. Our discussion will review the available published reports on pregnancy in females with RTH and our approach to the management of her antenatal care and foetal monitoring.