The size of growth hormone granules in pituitary adenomas producing acromegaly.

Measurements of the diameters of large numbers of granules in electron micrographs of pituitary adenomas in cases of acromegaly do not show that a typical size exists which allows of the retrospective diagnosis of the hormone secreted by the tumour. The granule diameters found in single cases show a normal distribution. The average values determined in 19 unselected cases of acromegaly range between 160 and 342 nm. They are also normally distributed about the mean for the entire group which is 238 nm. With histo-immunological electron microscopic techniques h GH can be demonstrated in small, medium and large granules. The size of hormone granules is determined by functional factors such as the speed of hormone synthesis and hormone release but not by the type of hormone secreted.