Specialist testing for pets’ difficult endocrine diseases
Author: Helen Evans
Endocrine diseases pose significant diagnostic challenges in veterinary medicine.
Clinical signs are often subtle and non-specific, and one endocrine disorder may predispose to another. It is, therefore, not uncommon for more than one condition to be present concurrently, further complicating the diagnosis.
Specialist endocrinology testing plays a vital role in helping to diagnose these complex cases – especially when clinical signs and initial testing fail to provide diagnostic clarity. This article focuses on a particularly challenging area: the diagnosis of canine insulinomas.
Common pancreatic tumours
Insulinomas are functional neuroendocrine tumours originating from pancreatic beta cells. Although insulinomas are considered to be rare, they are the most common pancreatic tumour in dogs and predominantly affect medium to large breeds, with the German shepherd, boxer, golden retriever and Labrador retriever showing increased predisposition1.
Although no definitive histological criteria exist for malignancy, insulinomas are usually associated with metastasis, and approximately 95 per cent of canine insulinomas are considered malignant2.
Pathophysiology
In healthy patients, blood glucose regulation involves close hormonal control, with insulin secretion rates responding to changes in blood glucose concentration. When blood glucose concentrations rise, an increase occurs in the rate of glycogenesis and a corresponding increase in insulin secretion by beta cells.
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Equally, when blood glucose concentrations decrease, insulin synthesis and secretion is inhibited, limiting tissue utilisation of glucose and allowing blood glucose concentrations to increase. Counter-regulatory hormones include glucagon and adrenaline, released in the immediate term, and cortisol and growth hormone, which are involved in longer-term control.
In cases of insulinoma, the pancreatic beta cells are unresponsive to hypoglycaemia and counter-regulatory control, resulting in uncontrolled secretion of insulin and profound hypoglycaemia. The precise mechanisms underlying the excess insulin secretion by insulinomas and the impaired cellular response to hypoglycaemia are not well understood. However, recent research suggests up-regulated glucokinase expression may be an important factor3.
Clinical signs of insulinoma
The clinical signs of insulinomas are related to the associated hypoglycaemia. Glucose is the primary energy source for the brain and nervous system and – in a hypoglycaemic patient – low blood-glucose results in reduced diffusion of glucose across the blood-brain barrier. This has a particularly profound impact on the nervous system and the most common clinical signs reflect this (Table 1).
Seizures, weakness and collapse are typically seen. Muscle tremors, nervousness and hunger may also occur due to a hypoglycaemia-induced activation of the autonomic nervous system.
In the early stages, signs may only be seen following fasting, exercise or excitement, and affected dogs will be clinically normal between episodes.
| Clinical Signs | Number of Dogs (percentage) |
| Seizures | 167 (52) |
| Weakness | 134 (42) |
| Posterior paresis | 106 (33) |
| Collapse | 89 (28) |
| Muscle fasciculations | 60 (19) |
| Ataxia | 59 (18) |
| Polyphagia | 22 (7) |
| Polyuria and polydipsia | 18 (6) |
Table 1. Most common clinical signs in 320 dogs with insulinomas4
Diagnostic challenges
Due to the intermittent and non-specific nature of the clinical signs, insulinomas present significant diagnostic challenges.
Demonstrating inappropriate insulin secretion can also be technically challenging, as blood glucose concentrations may be normal at the time of sampling. Additionally, multiple other causes of hypoglycaemia must be ruled out, including sepsis, hepatic disease and hypoadrenocorticism.
Even when hypoglycaemia is documented and other differential diagnoses have been excluded, the interpretation of insulin results can be complex.
The article continues beyond this point. Read the full article https://www.vettimes.com/clinical/small-animal/specialist-testing-for-pets-difficult-endocrine-diseases
Original publication: Vet Times (2025), Volume 55, Issue 6, Pages 6-8
About the author
Helen Evans is co-founder and manager of NationWide Specialist Laboratories. With a background in biological sciences, she began her career developing assays at St Thomas’ Hospital in London before moving into the veterinary diagnostics field. She has over 20 years of experience in veterinary clinical laboratories and has played a key role in developing specialist assays at NationWide Laboratories. Her areas of expertise include endocrinology, biochemistry, and veterinary medicine.
More information on our specialist and endocrinology services is available here https://nwlabs.co.uk/cambridge-handbook
