Endocrine Abstracts

Cabergoline has long been used to treat prolactinomas for symptomatic, radiological and biochemical resolution of pituitary tumours. As clinicians we are well-versed at screening for physical side effects, but are we holistic enough? We present two cases illustrating the damaging social consequences of cabergoline treatment for prolactinomas.

Case 1

A 49-year-old married father of two presented with a seizure in April 2018. MRI showed 2.3 × 2.5 × 2.5 cm sellar and suprasellar mass which compressed the optic chiasm as well as an unrelated grade 2 oliogodendroglioma which was later debulked. Prolactin levels at presentation were 50.205. The remainder of his pituitary profile showed TSH 0.75, T4 9.5, ACTH 6.9, cortisol < 28, LH 0.9, FSH 1.3, testosterone 1.7, GH < 0.05. He was started onto cabergoline 500 mg twice weekly and 4 mg prednisolone daily. His prolactin fell from 50.205 to 816 over 5 months. Eighteen months later, he reported a change in sexual behaviour, the use of escort services and sexual involvement with work colleagues. Cabergoline was discontinued in November 2019. Repeat prolactin levels in December 2019 were 583 and testosterone of 12.

Case 2

A 56-year-old man in a long term steady same- sex relationship, presented with erectile dysfunction and low energy in October 2018. His prolactin was 3.464 and testosterone 4.5. The remainder of his pituitary profile revealed TSH 1.07, T4 11.3, cortisol 189, LH 1.8, FSH 2.1, testosterone 4.5 and SHBG 41. An MRI scan of his pituitary revealed a 11 × 9 mm pituitary adenoma. He was commenced onto Cabergoline 250 mg once weekly. His prolactin fell from 2464 to 18 within 5 months, with testosterone levels of 18.9. In October 2019, his worried partner reported a change in personality and hypersexuality. Cabergoline was stopped. However, due to the patient’s concerns of a return of low libido, testosterone replacement was commenced. His prolactin in November 2019 was 1942. These cases raise important ethical questions. Firstly, how much of the hypersexual behaviour observed is a direct side effect of dopamine agonist treatment and how much is a behavioural consequence of the rise testosterone? Secondly, when cabergoline treatment results in behavioural side effects such as the failure of a marriage or financially crippling gambling, who takes responsibility when huge debts emerge and family units collapse? We must be cautious when prescribing and monitoring dopamine agonist therapy to avoid social harm to patients and balance this with depriving patients of effective non-invasive treatments.