30 | The complete guide to caring for cats with acromegaly

PodcastEndocrine
Written By Laura Jones

Today, we’re talking all about a very common but underdiagnosed cause of diabetes in cats - acromegaly.

 

With around 25% of diabetic cats affected, it’s a disease that we’re encountering more and more - and to give the best care we can to these patients, we need to understand what acromegaly is and how it affects our patients - which is precisely what we’re diving into today.

So what actually IS acromegaly?

Acromegaly—also known as hypersomatotropism—is the excessive release of growth hormone. Usually, this is caused by a benign functional tumour on the anterior pituitary gland itself, where tumour cells hypersecrete growth hormone.

Growth hormone is both a counter-regulatory hormone (one that causes sudden increases in glucose levels) and a hormone that causes insulin resistance.

The result is persistent hyperglycaemia and insulin-resistant diabetes mellitus—and actually, all cats with acromegaly will go on to develop diabetes.

It’s a common condition in older cats, usually 8-14 years, and it’s typically seen more commonly in males than females.

What signs do we see in an acromegalic patient?

These pituitary tumours are often slow-growing and may be present for many months before clinical signs appear.

Presenting signs are usually those of insulin-resistant diabetes. These patients tend to present with PUPD and polyphagia. However, they typically (but not always) present with net weight gain rather than weight loss - usually, the combination of polyphagia with weight loss is classic for diabetes mellitus. 

Patients may have previously been diagnosed with diabetes but responded poorly to increasing doses of insulin or changes in insulin type - because the persistent growth hormone release means that, even on high doses of insulin, their diabetes will not stabilise.

Because growth hormone is also responsible for growth (as the name suggests!), we often see changes to their body conformation and signs associated with diabetes. 

These patients tend to be larger, with an enlarged head, jaw, tongue and extremities. The paws, chin and skull are significantly enlarged, and these patients generally have increased muscle mass.

They also have organomegaly, with enlarged kidneys, liver, and endocrine organs.

Cardiovascular changes such as aortic aneurysm, cardiomegaly and cardiac murmurs may be present. These patients are usually at an increased risk of congestive heart failure if their disease progresses without treatment.

These patients also tend to have very tough skin, which makes things like blood sampling and IV catheter placement challenging!

So that’s what acromegaly is - but how do we diagnose it?

As we discussed in episode 28, these patients are usually diagnosed with diabetes mellitus first through normal bloodwork and urine analysis.

From here, a lack of response to treatment usually prompts testing for acromegaly, which we can do through a combination of blood tests and imaging.

Serum growth hormone levels or insulin-like growth factor 1 (IGF-1) levels are required for diagnosis. Unfortunately, feline growth hormone measurement is no longer possible, so IGF-1 concentrations are used to diagnose the condition, which is usually dramatically increased.

From here, definitive diagnosis requires advanced imaging of the pituitary region, which is achieved with CT. This allows us to measure the pituitary gland and use intravenous contrast media to easily identify a mass.

In addition to documenting a pituitary lesion and increased IGF-1 levels, we also need to exclude other causes of insulin resistance - such as hyperadrenocorticism and/or hyperthyroidism.

And once our patient is diagnosed, how will we treat them?

A few methods of treating acromegaly are described, but the most successful one by far is the surgical removal of the pituitary gland.

This procedure is known as a transsphenoidal hypophysectomy. Essentially, the pituitary gland is accessed via an intraoral surgical approach through the sphenoid bone. Because it’s not possible to remove just the pituitary tumour, the entire gland is removed.

From episode 26, we know that our pituitary gland releases a lot of hormones. No pituitary gland means no hormone release, and that means our acromegaly patients end up with other endocrinopathies postoperatively, requiring ongoing management.

In particular, these patients will end up with hypothyroidism and hypoadrenocorticism (Addison’s disease), requiring lifelong treatment and monitoring. They often also end up with central diabetes insipidus postoperatively due to a lack of ADH release - though this is usually transient. 

Our clients must be aware of this if they’re considering this treatment, especially if their cat is challenging to medicate.

What about non-surgical treatment?

Non-surgical treatments are also described. These include somatostatin analogues and dopamine agonists, but their success is limited. A new somatostatin analogue called pasireotide has succeeded in initial studies, but research is ongoing, and the drug is costly.

Radiation therapy is described as an alternative to surgery. This has low morbidity and mortality rates but shrinks the tumour slowly and risks radiation injury and damage to the surrounding tissues, including the hypothalamus.

Alternatively, clients may wish to manage the diabetes alone whilst not pursuing treatment of the pituitary mass. This is associated with a fair-to-good short-term prognosis and requires large doses of insulin divided into several daily doses.

However, the long-term prognosis is poor due to the other effects of the acromegaly. These patients tend to die of congestive heart failure, renal disease, or neurological signs associated with an expanding pituitary mass.

Suppose you do think your patient is acromegalic, and the client wishes only to pursue insulin treatment. In that case, it’s essential they know they’re only managing the diabetic signs, not treating the underlying condition - and it’s the changes associated with the underlying disease that are often fatal.

So that’s treatment sorted, but how will we nurse our acromegaly patient?

Aside from support during the initial diagnostics, most nursing care is postoperatively in a hypophysectomy patient.

These patients require intensive monitoring and nursing care in the acute postoperative period, as well as monitoring neurological status, cardiovascular status, glycaemic control, blood pressure, and hydration status.

Placement of a continuous glucose monitor is often a good idea postoperatively. This allows us to noninvasively monitor glucose levels intensively, guiding decisions about insulin administration until the insulin resistance resolves.

In addition, we need to regularly assess pain levels, administer appropriate analgesia, support voluntary food intake, and provide general nursing care.

Client education and support are vital when the patient is ready to leave the hospital. Our clients need to know what to do about glucose monitoring and insulin doses (for example, does the patient need any insulin at all anymore?), and they need education and support with their pet’s new diagnoses of Addison’s disease and hypothyroidism.

Though we cure their acromegaly and therefore cure their diabetes, we leave them with other endocrinopathies to manage - meaning our nursing support never stops for these patients; it just looks different as time goes on.

So there you have it! An overview of an increasingly common condition in our cats - acromegaly. If you’ve got more than a few diabetic cats on your books, there’s a good chance that one of them is affected - so consider suggesting testing for it in your hard-to-stabilise patients, and remember… even after successful treatment, the nursing care never stops for these patients!

Thanks so much again for joining me for another episode of the podcast! Don’t forget, if you want to join the demystifying diabetes webinar, you can grab one of the remaining tickets in the link below before July 10th - if you’re listening to the podcast on the day it goes live, that’s in 5 days! I’ll see you back here next week for the next episode in our endocrine series. In the meantime have a great week and i’ll speak to you very soon!

Did you enjoy this episode? If so, I’d love to hear what you thought - screenshot it and tag me on Instagram (@vetinternalmedicinenursing) so I can give you a shout-out and share it with a colleague who’d find it helpful!

Thanks for learning with me this week, and I’ll see you next time!

References and Further Reading

Laura Jones
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