The pituitary-thyroid axis following surgery for thyrotoxicosis: thyrotrophin-releasing hormone tests in diffuse thyroid hyperplasia and toxic uninodular goitre.

The pituitary-thyroid axis was assessed 1 month after surgery by thyrotrophin releasing hormone (TRH) testing in thirty thyrotoxic patients treated by subtotal thyroidectomy and eleven patients with toxic uninodular goitre. All toxic nodule patients gave essentially normal TRH responses and have remained clinically and biochemically euthyroid at follow-up. Only seven of the thirty subtotal thyroidectomy patients had normal TRH tests when assessed 1 month post thyroidectomy -sixteen patients showed increased response, six gave flat responses, and one showed an anomalous minimal response. Follow-up TRH tests 12 months postthyroidectomy have shown a tendency for TRH responsiveness to return towards normal, but two patients with flat TRH tests have required radioiodine for relapse and four TRH hyperresponders are currently receiving thyroxine replacement therapy.