Somatotropin secretion in hyperprolactinemia

1. HPL patients characteristically show depressed basal levels of STH. 2. Patients with HPL and radiologically confirmed pituitary adenoma show an altered response of the somatotropic structures to glucose challenge and marked circadian variations in the STH circadian pattern. 3. In patients without a radiological sign of pituitary adenoma STH levels are depressed but the circadian rhythm resembles the normal pattern; the STH fails to show a response to a glucose load and in GTT the STH concentration plot is flattened. 4. The severity of somatotropic functional alteration in HPL is not as important as the nature of the pathologic substrate which underlies the disease. 5. Studies on the circadian STH pattern and its fluctuations in GTT may provide objective criteria in the diagnosis of pituitary microadenoma.