Pitfalls in pituitary diagnosis: peculiarities of three cases

Due to the increasing availability and sensitivity of diagnostic methods, biochemical and imaging abnormalities of pituitary function and anatomy are becoming more frequent. Hyperprolactinaemia was found in three women without any prolactin (PRL) related clinical features. All three patients had normal libido, regular menses with evidence of ovulation, no galactorrhoea, and normal FSH, LH, TSH and free T4 serum levels. Magnetic resonance imaging (MRI) of the sellar region showed images that were compatible with pituitary microadenomas in all three cases. Due to the discordance between laboratory and clinical features, we searched for the presence of PRL aggregates with high molecular weight and low biological activity (macroprolactinaemia). Initially, we screened with a polyethylene glycol precipitation method, and then confirmed the presence of macroprolactinaemia by chromatography. All three cases screened positive for the presence of macroprolactinaemia. MRI alterations, compatible with pituitary microadenomas, may be due to true microincidentalomas, normal anatomical variations or imaging artefacts. In conclusion, we have described the presence of double diagnostic pitfalls that might lead to unnecessary medical or surgical intervention.