Pre-Vetoryl Cortisol

The ACTH stimulation test is validated for the diagnosis of hyperadrenocorticism and for the monitoring of mitotane therapy (Dunn et al 1995).

The ACTH stimulation test demonstrates that Vetoryl reduces cortisol production, and it was assumed to be a valid method of monitoring Vetoryl therapy when the product was first launched (Neiger et al 2002). However, the reliability (correlation with clinical response), repeatability, sensitivity and specificity (for diagnosing over treatment) were never tested (Ramsey 2010).

It has since been shown that there is poor correlation between the post-ACTH stimulation cortisol result and the clinical response of dogs receiving Vetoryl (Wehner et al 2013, Macfarlane et al 2016). This is probably because post-ACTH cortisol does not reflect average daily cortisol.

If ACTH stimulation tests are repeated in the same dog with the same level of clinical control on the same dose of Vetoryl the results may be markedly different (Ramsey et al 2016). This is probably because the suppression of cortisol production by Vetoryl varies in timing day to day.

The post-ACTH stimulation cortisol result may also indicate that a dog is being over treated when in fact it is not (Midence et al 2015). This is because while Vetoryl can induce a temporary over suppression of the cortisol production that ACTH stimulation cannot overcome, this effect may not last for the full inter-dose period. The result is that ACTH stimulation tests lack sufficient specificity for the diagnosis of hypocortisolism in a dog being treated with Vetoryl.

The timing of the ACTH stimulation test relative to the administration of Vetoryl significantly affects the results obtained (Bell et al 2006). However, published target reference ranges are broadly similar (Ramsey, 2010).

In addition, dogs that are unwell because of another condition could have alterations in the post-ACTH stimulation cortisol results because of that condition. This has not been investigated.

Many other methods investigated to date such as the urine cortisol:creatinine ratio, ‘basal’ cortisol, cortisol:ACTH ratio and haptoglobin have not proven to be better than the ACTH stimulation test against which they were compared.

As a result of a shortage of tetracosactide, researchers at the University of Glasgow began to investigate alternative methods of monitoring dogs on Vetoryl treatment whilst continuing to perform ACTH stimulation tests. The researchers developed a standardised questionnaire that provided a semi-quantitative assessment of control. Various alternative monitoring methods and the results of the ACTH stimulation tests were then compared to the results of the questionnaire (Macfarlane et al 2016).

The method that best predicted the results of the owner questionnaire was the cortisol measured just BEFORE Vetoryl administration (now called Pre-Vetoryl Cortisol monitoring) (Macfarlane et al 2016).

Read a summary of the Macfarlane et al 2016 paper here

Click here to access the full Macfarlane et al 2016 paper (external link)

The Glasgow results were then communicated to others in the scientific community and a multicentre clinical trial compared the repeatability of Pre-Vetoryl Cortisol monitoring with post-ACTH cortisol tests. The results showed that Pre-Vetoryl Cortisol was considerably more repeatable than post-ACTH cortisol (Ramsey et al 2016). So, a dog on a particular dose of Vetoryl is more likely to have similar result when retested using Pre-Vetoryl Cortisol measurements than using ACTH stimulation tests.

Further work is still on-going in Glasgow, Zurich, Utrecht and Bologna Universities.

• The most important factor to consider when re-evaluating a patient receiving Vetoryl is to carefully consult with the owner regarding the dog’s clinical response at home. This critical part of the assessment is often overlooked in a busy clinic but is vital to ensure good compliance, safety and optimal response to therapy
• Motivating an owner to take control of their dog’s condition, by providing them the tools to enable consistent and effective monitoring is of benefit to everyone involved in the dog’s care. Systematic and frequent record keeping at home could potentially allow an owner to detect subtle changes sooner, which further enhances safety. In addition, it could also alert them to the possibility that the adequacy of their dog’s control is changing, prompting a sooner appointment than would otherwise be scheduled
• Owners who report over the phone that their dog is unwell should be seen at their veterinary practice so that iatrogenic hypoadrenocorticism can be investigated (through cortisol results and the results of haematology, biochemistry and electrolyte analysis)

• Questions regarding the common clinical signs of hyperadrenocorticism should be asked, such as thirst, urination frequency and volume, appetite, coat quality and general demeanour. In addition, questions which might point to the dog having signs of over-suppression at home (iatrogenic hypoadrenocorticism), or that they may have another concurrent condition making them unwell, are critical to ensure patient safety. These include any signs of vomiting, diarrhoea, lethargy and decreased appetite. A standardised questionnaire is available to help clinicians

Suitability

Initial assessment of patient suitability for this approach should be considered using the coloured boxes below.

Appointment

• Book an appointment just before the next Vetoryl dose is due
• If the dog is normally given Vetoryl at an inconvenient time (e.g. 6 am) then ask owner to give at a convenient time from at least the day before (e.g. 9 am)
• Make sure the owner has not given Vetoryl and that nothing stressful has happened that morning (e.g. vomiting, injury)  
• Ensure the owner has completed the Quality of Life Questionnaire
• Take history and quickly examine the dog, checking for signs of HAC

Sample

• Take sample immediately after examination and before administration of Vetoryl
• 1 to 2 ml of blood in heparin or serum tube
• Can be separated and stored for up to 1 week
• Send to an external laboratory participating in an external quality assurance scheme e.g. the  ESVE or SCE programmes, and preferably that uses a Siemens IMMULITE^® or a method that has been validated against this machine

Can I use Pre-Vetoryl Cortisol monitoring in dogs being treated with Vetoryl twice daily?

Yes. All the results so far suggest that Pre-Vetoryl Cortisol monitoring is suitable for dogs treated twice daily. Indeed given that the duration of action of Vetoryl is under 12 hours it is theoretically possible that the performance of Pre-Vetoryl Cortisol monitoring would be better in dogs treated twice daily than those treated once daily.

How do I use PVC in a patient receiving Vetoryl twice daily?

PVC can either be collected prior to the morning or the evening dose - dependent on what best suits the owner and the practice.

If monitoring prior to the morning dose:
The previous evening’s dose should be administered as normal. The PVC appointment should then be booked at the time of, or up to 2 hours after, the dog’s morning dose time. I.e. if the dog is normally dosed at 8 AM the appointment can be booked between 8 AM and 10 AM, but the morning dose of Vetoryl should be delayed until the PVC blood sample is obtained. Once the blood sample has been collected the dog can be fed it’s morning meal and Vetoryl administered.

If monitoring prior to the evening dose:
The patient’s morning dose should be administered as normal. The PVC appointment should then be booked at the time of, or up to 2 hours after, the dog’s evening dose time. I.e. if the dog is normally dosed at 5 PM the appointment can be booked between 5 PM and 7 PM, but the evening dose of Vetoryl should be delayed until the PVC blood sample is obtained. Once the blood sample has been collected the dog can be fed it’s evening meal and Vetoryl administered.

Can I use Pre-Vetoryl Cortisol monitoring in dog with diabetes and hyperadrenocorticism?

Yes. Although the evidence is perhaps a little weaker because fewer dogs have been monitored like this, all the results so far suggest that Pre-Vetoryl Cortisol monitoring is suitable for dogs with diabetes and hyperadrenocorticism.

Can I use Pre-Vetoryl Cortisol monitoring in dogs with adrenal dependent hyperadrenocorticism?

Yes. Although the evidence is perhaps a little weaker because fewer dogs have been monitored like this, all the results so far suggest that Pre-Vetoryl Cortisol monitoring is suitable for dogs with adrenal tumours.

Given that there is so much emphasis placed on using the control of the clinical signs to monitor Vetoryl, why bother with Pre-Vetoryl Cortisol testing?

This sounds like a good idea but there is no way of detecting too little cortisol in an otherwise well dog until it becomes unwell - and hypocortisolism can be dangerous. Another useful feature of Pre-Vetoryl Cortisol measurements is that, in the dog with clinical signs of hyperadrenocorticism, the measurement may aid dose adjustment. In addition, owners may not be entirely reliable and veterinarians may not be overly familiar with this case of hyperadrenocorticism or the condition in general.

Are owners reliable enough?

The majority of owners, especially those committed to treating hyperadrenocorticism, are unlikely to miss signs. It is also possible that by placing more emphasis on their role as the primary monitors of their own dog’s condition, they may be more likely to notice signs sooner. In addition, it is hoped that they may also be more observant of signs of poor control. However some owners are unreliable or do not directly engage with the attending veterinarian. In these circumstances in-clinic assessment and monitoring with Pre-Vetoryl Cortisol should be more frequent if possible.

Direct your clients to the Vetoryl owner website. Here they will be able to keep detailed logs and email them to you directly. However, printed log books can also be ordered by your practice free of charge if the owner is not able to use the online version for any reason.

1) BELL R., NEIGER R., MCGROTTY Y. & RAMSEY I. K. (2006) Study of the effects of once daily doses of Vetoryl on cortisol concentrations and responsiveness to adrenocorticotrophic hormone in hyperadrenocorticoid dogs. Veterinary Record 159: 277-281

2) BURKHARDT W. A., BORETTI F. S., REUSCH C. E. & SIEBER-RUCKSTUHL N. S. (2013) Evaluation of baseline cortisol, endogenous ACTH, and cortisol/ACTH ratio to monitor trilostane treatment in dogs with pituitary-dependent hypercortisolism. Journal of Veterinary Internal Medicine 27: 919-923

3) COOK A. K. & BOND K. G. (2010) Evaluation of the use of baseline cortisol concentration as a monitoring tool for dogs receiving trilostane as a treatment for hyperadrenocorticism. Journal of the American Medical Association 237: 801-805

4) GRIEBSCH C., LEHNER, C., WILLIAMS G. J., FAILING K. & NEIGER R. (2014) Effect of Vetoryl on hormone and serum electrolyte concentrations in dogs with pituitary-dependent hyperadrenocorticism. Journal of Veterinary Internal Medicine 28: 160-165

5) MACFARLANE L., PARKIN T. AND RAMSEY I.K. (2016) Pre-trilostane and 3-hour post-trilostane cortisol to monitor trilostane therapy in dogs. Veterinary Record 179: 597-605

6) MIDENCE J. N., DROBATZ K. J. & HESS, R. S. (2015) Cortisol Concentrations in Well-Regulated Dogs with Hyperadrenocorticism Treated with Vetoryl. Journal of Veterinary Internal Medicine 29: 1529-1533

7) NEIGER, R., RAMSEY I., O'CONNOR J., HURLEY K. J. & MOONEY C. T. (2002) Vetoryl treatment of 78 dogs with pituitary-dependent hyperadrenocorticism. Veterinary Record 150: 799-804

8) RAMSEY I. K. (2010) Trilostane in dogs. Veterinary Clinics of North America: Small Animal Practice 40: 269-283

9) RAMSEY I. K., MACFARLANE L., FRACASSI F., GALAC S. & REUSCH C. (2016) The repeatability of various cortisol measurements in clinically stable dogs with hyperadrenocorticism being treated with Vetoryl (Abstract) European College of Veterinary Internal Medicine Congress, Gotenburg (published in Journal of Veterinary Internal Medicine 17: 737DO - 10.1111/jvim.14600)

10) WEHNER A. GLOECKNER S., SAUTER C., KRUSE D., STOCKHAUS C. & HARTMANN, K. (2013) Association between ACTH stimulation tests, clinical signs, and laboratory parameters in dogs with hyperadrenocorticism treated with Vetoryl. (Abstract) European College of Veterinary Internal Medicine Congress, Liverpool

11) DUNN K. J., HERRTAGE M. E., DUNN J. K. (1995) Use of ACTH stimulation tests to monitor the treatment of canine hyperadrenocorticism Veterinary Record 137(7):161-5

Pre-trilostane and three-hour post-trilostane cortisol to monitor trilostane therapy in dogs. Vet Rec 179: 597-605

• In a study of 93 well dogs with hyperadrenocorticism, the Pre-Vetoryl Cortisol, the 3-hour post Vetoryl cortisol and the post-ACTH cortisol were analysed and compared to the results of the categorisation of clinical control, as determined by the results of the owner questionnaire
• The results showed that although not perfect, both the Pre-Vetoryl Cortisol and the 3-hour post-Vetoryl cortisol were better at predicting clinical control, compared to the post-ACTH stimulation cortisol. When under controlled dogs were compared to controlled dogs both the sensitivity and specificity of the Pre-Vetoryl Cortisol was better than either the 3-hour post Vetoryl or the post-ACTH stimulation cortisol at differentiating between the two groups
• In the study there were eight results from dogs which had a post-ACTH stimulation cortisol result of ≤ 40nmol/l, yet all dogs were well with no clinical signs at home of hypoadrenocorticism. It could be argued that these dogs should have their Vetoryl stopped or the dose reduced
• Follow-up of these eight dogs showed that none developed signs of hypoadrenocorticism, despite 50% having had no dose alteration. The other 50% had their Vetoryl dose reduced as the primary clinician was concerned about the possibility of hypoadrenocorticism, however there were no suggestive signs before or after the reduction
• These findings agree with another recent study (Midence et al 2015) which showed that there is a small subset of dogs that are clinically well but have a low post-ACTH stimulation cortisol (test started 3-6 hours after the Vetoryl was given). This study demonstrated that repeating the ACTH stimulation test 9-12 hours after Vetoryl allowed for continued therapy without dose alteration if the post ACTH stimulation cortisol at this second point was above 55 nmol/l. No dogs in the follow-up period (>88 days) developed signs consistent with hypoadrenocorticism. As it is known that the cortisol 12 hours after Vetoryl is not significantly different from cortisol 24 hours after Vetoryl (Griebsch et al 2014), this study is similar to the hypothesis of the Macfarlane et al 2016 paper. If the Pre-Vetoryl Cortisol is ≥ 40 nmol/l and the patient is well, then a dose reduction may not be required (even if the post-ACTH stimulation cortisol contradicts this)
• In the study, there were six test results that had a low Pre-Vetoryl Cortisol result (≤40 nmol/l). In all six cases, the dogs were clinically well according to the results of the owner questionnaire. In four of these dogs only the Pre-Vetoryl Cortisol result was low i.e. the post-ACTH stimulation performed later in the day was ≥40 nmol/l). In one of these dogs, the dose was not altered and the dog developed subsequent signs which were possibly consistent with hypoadrenocorticism (vomiting, diarrhoea and a low Na:K ratio) 3 months later. In another dog, the dose was reduced despite the owner reporting the dog was well. After the dose reduction the owner reported the dog had become much more interactive and had a brighter demeanour. Although not a definitive diagnosis, in both cases a low Pre-Vetoryl Cortisol was perhaps a more sensitive indicator that the dogs were being over-suppressed, than the post-ACTH stimulation cortisol
• The 3-hour post Vetoryl  cortisol was low in a large number of dogs in the study (31/110), which is similar to findings in other recent studies (Burkhardt and others 2013; Cook and Bond 2010). This means that it had very low specificity at highlighting dogs at risk of over-suppression

Conclusions

• There are challenges in achieving stability of hyperadrenocorticism whilst maintaining safety. Monitoring of patient’s condition should move towards a more comprehensive approach, placing more emphasis on at-home monitoring by the owner and not relying exclusively on laboratory measurements
• Whilst it could be seen as desirable to rely solely on owner observations, an objective tool is also required to ensure that treatment remains safe for those dogs whose owners’ observational skills are inadequate or for those dogs who are developing sub clinical hypoadrenocorticism that could progress to an overt, life threatening disease. In addition, taking a good history takes time and this is not a luxury that veterinarians always have
• Traditionally the post-ACTH stimulation cortisol has been used as the primary laboratory tool to guide dose adjustments and to detect those dogs at risk of iatrogenic hypoadrenocorticism. There is now consistent evidence that the correlation between the post-ACTH stimulation cortisol and clinical control is poor. There is also evidence that supports the continued use of Vetoryl in a sub-set of dogs that are clinically well but have a low post-ACTH stimulation cortisol which had previously thought of as having sub-clinical hypoadrenocorticism and being at risk of overt clinical signs
• The Pre-Vetoryl Cortisol, although not perfect, is a promising new tool which has been shown to have better correlation with clinical control reported by owners. In addition, there are some instances when this result may be better than the post-ACTH stimulation cortisol at detecting iatrogenic hypoadrenocorticism. This test is easier, less expensive and has no side effects, offering a more practical solution for busy practice life

Further studies into the use of Pre-Vetoryl Cortisol (perhaps with haptoglobin) are ongoing to develop the optimal monitoring tools for both veterinarians and owners of dogs treated with Vetoryl.

(Agreeing Language In Veterinary Endocrinology - a joint project of the European Society of Veterinary Endocrinology and the Society of Comparative Endocrinology)

Recent data from multiple sources have shown a lack of correlation between ACTH stimulation test results and clinical status of hyperadrenocorticism dogs treated with trilostane.

The ACTH stimulation test has not been shown to accurately indicate trilostane underdosing, overdosing or appropriate dosing.

The ALIVE consensus is therefore that the value of the ACTH stimulation test, as well as the optimal ACTH stimulation test timing and interpretation of results at various times after trilostane administration are not established. Additionally, the basal (post-pill) cortisol does not seem to accurately reflect adrenal reserve.

Recent data suggest pre-pill cortisol just prior to trilostane dosing to be superior to the traditional ACTH stimulation test. Some aspects of this alternative monitoring method, such as the pre-pill timing and number of samples, are still being debated and investigated.

The committee recommends future investigations to focus on developing superior monitoring methods.

For any cortisol measurement to be relied upon, this should be performed by the same laboratory and the laboratory should be conducting regular rigorous quality assurance (e.g. by participating in the ESVE or SCE Laboratory Quality Assurance Scheme). Dogs should also be as calm as possible before sampling.

Regardless of the chosen monitoring method, the ALIVE committee strongly recommends clinicians to pay meticulous attention to the clinical picture of treated patients when making trilostane-dose alteration decisions.