No Synacthen? What to do?


We have had a few enquiries recently regarding how to monitor Cushing’s, and how to diagnose Addison’s disease, when Synacthen (for ACTH stimulation testing) is difficult to obtain. So here is some information for you.

Monitoring Cushing’s disease (when treated with Vetoryl/Trilostane):

To monitor control of Cushing’s (in the absence of ACTH-stimulation testing), we can use the ‘pre-pill’ serum cortisol level. Obtain a serum sample approximately one hour either side of when the usual Vetoryl/Trilostane dose is due (we are measuring the expected peak cortisol level). For example, if a client is due to give Vetoryl/Trilostane at 8am, a blood sample for serum cortisol can be taken anytime from 7-9am. The animal would then receive its Vetoryl/Trilostane dose after the blood sample is taken. 

Guidelines for pre-Vetoryl cortisol results:

Clinical signs and history are important in interpretation of pre-Vetoryl cortisol monitoring.  The presence of PUPD, alopecia, lethargy, distended abdomen, panting etc. may suggest inadequate control, whereas GI signs, inappetence and weakness may suggest the need for a decreased dose.  This monitoring technique is not recommended for dogs that appear highly stressed/aggressive in clinic.  In dogs that are clinically unwell (e.g. vomiting, diarrhoea, inappetence), Vetoryl should be stopped and an ACTH-stimulation test performed.**

Pre-Vetoryl cortisol (nmol/L) in dogs with no clinical signs:

<40 Re-evaluate clinical signs, consider lower dose, recheck in one month

40-138 Keep current dose, recheck in three months

>140 Re-evaluate clinical signs, consider BID dosing or small increase in dose, recheck in one month.

Pre-Vetoryl Cortisol (nmol/L) in dogs with persistent clinical signs of HAC:

<40 Re-evaluate diagnosis of HAC

If cortisol is not decreased, consider increased dose (increase frequency to BID first), and recheck in one month.

Further information can be found at    

**In the absence of synthetic ACTH, for unwell dogs, we need to evaluate all routine data (CBC, biochemistry, blood glucose, urinalysis, survey imaging) to identify any concurrent disease. Monitoring then resumes once concurrent disease is stabilised. Basal cortisol can be used to evaluate for potential clinically significant hypocortisolemia.

Diagnosing Addison’s disease and cases where there are normal LDDST results with suspect Cushing’s disease:

In these cases we rely heavily on clinical presentation, and utilising all available routine data at our disposal (e.g. CBC, biochemistry, blood glucose, urinalysis and imaging).  The more findings that fit the endocrinopathy, the more confidence we have.

Addison’s disease is especially difficult without ACTH-stim testing, however we can use additional testing to help exclude the diagnosis (e.g. basal cortisol >55 nmol/L, UCCR >3).

We’re always happy to discuss any of the more tricky endocrine cases with you. Talk to us today—0800 GRBIBBLES.