Pituitary resistance to L-thyroxine after thyroidectomy. A case report

The clinical and laboratory findings in a 29-year-old Saudi Arabian woman were compatible with a state of resistance to thyroid hormones by the pituitary gland. Symptoms of hypothyroidism, amenorrhoea and secondary infertility developed 10 years after partial thyroidectomy for an euthyroid goitre. Before therapy, serum thyroxine (T4) and thyroid-stimulating hormone (TSH) values were elevated; serum tri-iodothyronine (T3) value was at the upper limit of normal while %T3 resin uptake and serum free T4 level were both normal. Treatment with L-thyroxine 150 micrograms/dl was not effective. After this was increased to 200 micrograms/d, serum T4 value rose, TSH was still elevated and there was improvement in symptomatology, and a return of both menses and fertility.