Start low, go slowly - mental abnormalities in young prolactinoma patients under cabergoline therapy.

Background Prolactin-secreting pituitary adenomas in childhood and adolescence are rare. First-line therapy consists of dopamine agonists (DAs) like cabergoline. Experience in treating prolactinomas in paediatric and adolescent patients is limited. Methods This study was a retrospective analysis of clinical data, laboratory data, radiological findings and medical treatment of paediatric and adolescent patients with prolactinomas between 2009 and 2018. Results Our cohort of nine patients had a median age at diagnosis of 13 years (range 5-17). Main presenting symptoms were weight gain, disorders of the pituitary-gonadal axis and headache. Treatment with cabergoline resulted in a marked reduction in prolactin concentration in all nine patients. Tumour mass reduction was confirmed by magnetic resonance imaging (MRI) scan in seven patients. Noteworthy is that cabergoline therapy triggered frequent adverse effects in a total of eight patients - seven of whom suffered from mental disorders, five of whom had neurological symptoms and five of whom had gastrointestinal problems. The adverse effects occurred at a median dose of only 0.5 mg/week (range 0.25-2.0). Most symptoms were alleviated after the cabergoline dose was lowered. Therapy discontinuation was not necessary in any patient. Conclusions Cabergoline effectively lowers prolactin levels and may reduce tumour mass in paediatric and adolescent patients with prolactinomas. Potential adverse effects may include mental disorders and behavioural problems even at low cabergoline doses. Low starting doses and careful individual dose adjustments are required to enable therapy adherence.