The aim of this study was to correlate lesions of the pituitary gland with hormonal dysregulation. The hormonal status of 63 children was correlated with MRI findings of the pituitary gland. Two radiologists judged the MRI examinations without knowledge of the hormonal situation. The reliability of the diagnosis "adenoma" was evaluated in five steps from 0-100% for each sequence. A microadenoma was found in six of 14 children with hyperprolactinemia and in six of eight patients with increased IGF-I/IGFBP-3. However, microadenomas were also detected in eight of 28 children without hormonal dysfunction (clinical feature: obesity). The adenomas were seen best in a dynamic sequence after gadolinium administration. An expansive growing macroadenoma was found in one of 13 patients with hypopituitarism. We found a relatively high number of microadenomas even in children without any hormonal dysfunction. Taking into account the reported autopsy results (6.1-27% occult microadenomas), we suggest that the MRI diagnosis "microadenoma" is made too frequently if usual MRI criteria are used. Patients with increased levels of IGF-I/IGFBP-3 had a high incidence of microadenoma (up to 87.5%). Hyperprolactinemia was associated with microadenomas in about 43% (-57%) of patients (nearly on the same level as children without hormonal dysfunction). Therefore unspecific stimulation of the pituitary gland with consecutive increased volume seems to be responsible for hyperprolactinemia in many of these patients.