Carney complex is a multiple neoplasia and lentiginosis syndrome. Acromegaly due to growth hormone (GH)-producing adenomas has been considered the only pituitary-related manifestation of the complex. In the present study, seven patients with Carney complex, who belonged to three unrelated kindreds and had relatives with acromegaly, were investigated for the presence of GH and prolactin (PRL) secretion abnormalities (familial cases). In addition, four patients with the complex and no family history of the complex were studied (sporadic cases). Seven of the patients were female and four were male; their mean age was 24.27 +/- 4.34 years. Sampling every 20 min for one hour in the morning and under fasting and unstimulated conditions was performed in all patients, for determination of serum PRL levels. Insulin-like growth factor-I (IGF-I) levels and magnetic resonance imaging (MRI) of the pituitary were also obtained. Patients who had elevated IGF-I levels underwent investigation for acromegaly by oral glucose tolerance test and thyrotropin-releasing hormone. Seven of the 11 patients (63.6%) had moderately high PRL levels (mean Z score value 2.12 +/- 0.66); three of these patients also had elevated IGF-I levels but a negative investigation for acromegaly. All patients had negative pituitary MRI. The patient with the highest PRL levels underwent 24-hour sampling every 20 min, which demonstrated a higher baseline secretion of this hormone with preservation of its circadian pulsatility. Hyperprolactinemia was present in two siblings and a parent-child pair. We conclude that prolactin hypersecretion, albeit mild, appears to be frequent in patients with Carney complex, is inherited in an autosomal dominant manner in kindreds with the syndrome, and may be associated with elevated IGF-I levels in some, but not all, patients.