Rational testing: Interpreting raised serum prolactin results

A 29 year old woman working in a solicitor’s office presented with secondary amenorrhoea and was found to have a serum prolactin of 2940mIU/L (upper reference limit < 600) and TSH of 5.2mIU/L (reference range 0.27-4.2). She had a history of depression and had previously been treated for anxiety and hyperthyroidism. There was no history of acne or hirsutism and until 8 months before presentation, her periods had been regular. Her body mass index was 18kg/m2 compared to 19.8kg/m2 the previous year.