Endocrine Abstracts

A 68 yr old male with a history of type 2 diabetes presented with myalgia and girdle weakness affecting him on a frequent but episodic basis. Investigations confirmed Cyclical Cushing's Disease. Pituitary MRI was normal. Further investigations include bilateral inferior petrosal sinus sampling (BIPSS) which can help determine the origin of ACTH-dependent Cushing’s syndrome. After CRH-stimulation, a peak central to peripheral ACTH ratio of >3 suggests a pituitary ACTH source. BIPSS should be performed when the patient is hypercortisolaemic, to ensure that normal adrenocorticotroph cells are adequately suppressed. This can be difficult to achieve in cyclical Cushing’s syndrome, as cortisol levels fall between periods of peak output, which may be hard to predict. It has been suggested that cortisol should be measured immediately before BIPSS, but serum cortisol may remain within the reference range in Cushing’s syndrome, while urine cortisol results may not be available on a suitable timescale. In this case of cyclical Cushing’s , we measured salivary cortisol daily for 14 days. This suggested a 3–4 day cycle (in keeping with clinical symptoms). A more prolonged series of daily salivary cortisol measurements, together with a symptom diary, was undertaken to better predict peak output and date of BIPPS. This simple, non-invasive investigation enabled us to monitor the daily trend in cortisol and to plan BIPSS to coincide with predicted high cortisol levels.

Declaration of interest: There is no conflict of interest that could be perceived as prejudicing the impartiality of the research reported.

Funding: No specific grant from any funding agency in the public, commercial or not-for-profit sector.