HIGH PLASMA THYROTROPHIN LEVELS IN TWO PATIENTS WITH PITUITARY TUMOUR

Abstract

ABSTRACT Out of 62 patients with pituitary tumours two (B. M.: vascular tumour and D. G.: chromophobe adenoma) showed symptoms and signs of hyperthyroidism and high plasma thyrotrophin (HTSH) values (mean values 24.0 and 8.4 μU/ml respectively). A parallelism was found between the Human Thyroid Stimulating Hormone Research Standard A (HTSH RSA) and the plasma dilution curves suggesting identity between immunoreactive material and authentic HTSH. The biological TSH activity was determined by McKenzie bioassay. Methimazole administration did not induce any significant modification in case B. M. while in case D. G. it caused a further increase in plasma HTSH. The triiodothyronine suppression test carried out in patient B. M. failed to produce a full inhibition, suggesting an autonomous function of the TSH secreting system. Lysine-vasopressin was ineffective in promoting HTSH increases in both cases, while insulin induced hypoglycaemia provoked in case B. M. a prompt fall in plasma HTSH levels, followed by an increase over the base line. The data obtained in case B. M. are compatible with a TSH-induced hyperthyroidism, while those found in patient D. G., though suggestive, are not completely consistent with this interpretation.