A 71 year old lady presented to MAU with a recent onset of generalised weakness and a history of facial and periorbital swelling developing over seven years. She had also noticed hoarsening of her voice, cold intolerance, weight gain, constipation and reduced appetite. Admission blood tests showed marked hyponatremia of 113 mmol/l with severe hypothyroidism (TSH 45.24 mIU/l, fT4 1.1 pmol/l and TPO antibody 358 IU/ml). Subsequent tests confirmed SIADH (serum osmolality of 236 mOsmol/kg, urinary osmolality of 604 mOSmol/kg and urinary sodium 48 mmol/l). Other pituitary hormones were unremarkable (post-menopausal range of FSH and LH, random cortisol of 706 nmol/l and prolactin 159 mIU/l). Initial ECG showed sinus rhythm, rate 56 bpm with biphasic T wave in V2-5. CXR did not reveal any abnormality.
She was started on oral L-thyroxine 50 μg OD, which was increased to 100 μg OD after 4 days. She did not require liothyronine as she responded clinically well with L-thyroxine and given her abnormal ECG there were concerns about potentially provoking a cardiac event. It should be noted that widespread T wave inversions can be seen in myxoedema. Hydrocortisone was not given as she did not meet the clinical criteria for myxoedema coma.
Hyponatremia slowly responded to fluid restriction and resolved completely a month after starting L-thyroxine. Her TSH improved to 12.4 mIU/l after 4 weeks and normalised within 7 weeks of treatment.
On review two months later, her periorbital oedema is much improved (pre and post treatment photos compared), her voice is less hoarse and her gums have shrunk so much that she has had to get new dentures. T wave changes on ECG have resolved and echocardiogram shows normal ventricular function.