Isolated TSH deficiency with a partially empty sella

Isolated TSH deficiency is rare. The diagnosis is based on (i) symptoms and signs of thyroid hormone deficiency, (ii) demonstration of an absent or impaired TSH response to TRH and (iii) other pituitary hormones remaining intact. We report a 60-year-old female in whom isolated TSH deficiency was found, with a free thyroxine - 7.0 pmol/L (11 - 20), total triiodothyronine level -1.5 nmol/L (1.1 - 2.6) and thyroid stimulating hormone - 0.87 mU/L (0.38 - 4.3). A TRH test on two separate occasions demonstrated an inappropriately low TSH response. Computed assisted tomography revealed a partially empty sella and other pituitary hormones were demonstrated to be intact. We were unable to detect pituitary antibodies using indirect immunofluorescence on sections of monkey pituitary, Treatment with thyroxine improved this patient's symptoms and suppressed the TSH further.