CLINICAL update
Life without ACTH – hypoadrenocorticism Simon Clark is an associate at the Hamilton Small Animal Veterinary Centre (HSAVC) and a member of the CAV Executive Committee. Here he describes how adrenal diseases in companion animals have been diagnosed and managed in his clinic since Synacthen became unavailable, reducing the use of the ACTH stimulation test. This second of two articles discusses the options for diagnosis and monitoring of hypoadrenocorticism in dogs and cats without Synacthen.
Simon Clark , BVSc, MVM The ACTH stimulation test measures the adrenal gland’s response to an I/V injection of ACTH (Adrenocorticotropic hormone). ACTH is no longer extracted from cadavers, and a synthetic ACTH product is commercially available for human use, called Synacthen (SynACTH-en). Synacthen (Tetracosactide hexaacetate) is not a brand, but more akin to a nickname for an active ingredient. There are many different products containing Synacthen as the active ingredient. Some of these are licensed for human use in New Zealand, some are not. None are licensed for veterinary use in New Zealand. Synacthen became unavailable for purchase a few years ago because the only brands stocked by New Zealand distributors were listed under Section 29 of the Medicines Act (see Box 1). When this occurred, veterinarians at HSAVC divided up what they had into small aliquots and froze them. Even though some Synacthen products are licensed for human use, and so available for discretionary veterinary use, this availability is intermittent and unpredictable. I discussed how to diagnose hyperadrenocorticism and hypoadrenocorticism and how to monitor my patients with Sandra
Box 1: Section 29
Section 29 medicines are human medicines that are non-consented. These medicines don't have a current product registration with MedSafe (similar to a veterinary medicine being registered with ACVM), so according to Section 29 of the Medicines Act 1981 they can still be sold to and used by registered medical practitioners, but they cannot be sold to or used by anyone who isn't a registered medical practitioner (i.e. veterinarians). The Medicines Act is overseen by the Ministry of Health (MoH), and is therefore outside of the jurisdiction of MPI’s ACVM group. The Act went under review in 2019, and NZVA/VCNZ made a combined submission that addressed the animal welfare impacts of veterinarians not having access to Section 29 medicines. The MoH is still in the review process. Medications that fall under Section 29 may be imported by veterinarians through a Special Circumstances Approval process via MPI. The information can be found at: https://www.mpi.govt.nz/processing/agricultural-compounds-and-vet-medicines/veterinarymedicines/getting-a-veterinary-medicine-authorised/authorisation-of-veterinary-medicines-underspecial-circumstances/. MPI only issues the approval, they do not help facilitate the importation process. Some veterinary wholesalers may be able to assist with importation of products, on a case-by-case basis.
Forsyth, a clinical pathologist at SVS Laboratories and reviewed the 4th Edition of Canine and Feline Endocrinology (Feldman et al. 2015). Based on these sources I have been adopting new tests, and have found the options for diagnosing hyperadrenocorticism faster, easier and cheaper, and therefore much more convenient for the client than the tests using Synacthen. The ACTH stimulation test remains the gold standard for diagnosing hypoadrenocorticism. As hypoadrenocorticism is less common than hyperadrenocorticism, avoiding the use of Synachten on patients suspected of hyperadrenocorticism, as discussed in the first of these two articles, will save our reserves for diagnosing hypoadrenocorticism.
Summary of hypoadrenocorticism
The cortex of the adrenal gland produces three classes of hormones. Glucocorticoids (cortisol), mineralocorticoids (aldosterone) and androgens. Naturally occurring adrenocortical insufficiency in the dog has been recognised since the 1950s. The disease was first recognised in cats in the 1980s and has been much less researched leading to limited understanding of the disease in this species. Therefore, the following discussion will focus on diagnosis and monitoring in dogs. There are a variety of causes of hypoadrenocorticism including tumours, infections, autoimmune disease, and
Contact: Simonthevet@gmail.com
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Companion Quarterly: Official Newsletter of the Companion Animal Veterinarians Branch of the NZVA | Volume 32 No 3 | September 2021
