Endocrine Abstracts

A 27 years old girl presented with weight gain, hirsutism, fatigue, bruising and striae. On examination she was Cushingoid. On initial assessment, 3 out of 4 24 h urinary free cortisol collections were elevated. 0800 h serum cortisol was 280 nmol/l after 1mg dexamethasone given at 2300 h. After formal 48 h low and high dose dexamethasone suppression tests cortisols were 164 and 34 nmol/l respectively. Basal 0800 h ACTH was 33 ng/l. Given the clinical features and the discrepant biochemical results, cyclical Cushing’s syndrome was suspected. A 28 day collection of early morning urine cortisol to creatinine ratios showed a clear cyclical pattern of 4 days in length.

MRI pituitary and petrosal sinus sampling were arranged. To ensure petrosal sinus sampling was performed during a period of cortisol excess, 0800 h serum cortisol was measured and available immediately before sampling proceeded. MRI pituitary showed an 8 mm adenoma. Petrosal sinus sampling confirmed a pituitary source of ACTH with elevated left petrosal sinus to IVC ratio (14 basally and 18 after CRH). Cabergoline was commenced and titrated to a dose of 2 mg twice weekly across 4 weeks. After 2 weeks on this dose a repeat 28 day collection demonstrated normal daily cortisol to creatinine ratios and loss of the cyclicity. A mean 24 h serum cortisol profile on therapy was 310 nmol/l. Repeat MRI at 3 months showed no change in adenoma size.

At present no drugs have been shown to be effective in cyclical disease. Corticotroph adenomas express the dopamine receptor D2 subtype to which cabergoline binds with high affinity. This is the first reported case of successful use of cabergoline therapy in a patient with confirmed cyclical Cushing’s disease. There is still the very rare possibility that this patient may have 2 simultaneous cortisol cycles thus making therapy assessment difficult. Currently continuing use of cabergoline appears worthwhile.