The endocrine system is crucial in regulating metabolism, growth, reproduction, and homeostasis in dogs. Disorders of the endocrine system occur when there is too much or too little hormone produced by glands, which can lead to multisystemic dysfunction.
Although not as visual or as obviously problematic as orthopaedic or gastrointestinal illness, endocrine disease can dramatically impact a dog’s quality of life and lifespan (Bugbee et al., 2023). In this blog, we aim to provide an all-encompassing, timely discussion of the most common disorders of the canine endocrine system using the most recent research (2020-2025) and provide tips for owners and veterinarians when providing care for clients.
Key disorders that we will discuss are:
- Hypothyroidism (canine)
- Hyperadrenocorticism (Cushing’s syndrome)
- Hypoadrenocorticism (Addison’s disease)
- Diabetes mellitus (canine)
For each, we will discuss: what it is, how it presents (symptoms/signs), how it is diagnosed, key recent advances, and how to manage/monitor.
Canine hypothyroidism
Hypothyroidism in dogs is most commonly primary, meaning the thyroid gland is not producing a sufficient amount of thyroid hormone (thyroxine/T4) and triiodothyronine (T3). This leads to a systemic slowing of metabolism (Heseltine, 2024).
Signs
As thyroid hormone affects almost all body systems, all clinical signs are variable and possibly insidious:
- Lethargy, mental dullness, and exercise intolerance.
- Weight gain with no increase (or possibly decrease) in appetite.
- Cold intolerance, seeking warmth/hypothermia.
- Dermatologic changes: Non-pruritic bilateral alopecia (especially ventral trunk, thighs, tail base), poor hair regrowth, excess shedding, hyperpigmentation, and sometimes secondary infections.
- Reproductive disorders: anestrus or infertility in intact females; testicular atrophy, and low libido in males.
- Occasionally, neurologic signs (rare): Laryngeal paralysis, facial nerve paralysis.
Recent studies have shown changes in metabolic markers: dogs with low thyroxine had altered metabolite profiles (glycoprotein acetyls, lipids) in an NMR metabolomics study.
Diagnosis
There are multiple challenges associated with the diagnosis of hypothyroidism in dogs, as there can be a significant overlap of clinical signs with several other diseases and “euthyroid sick” syndrome (thyroid values suppressed due to a non-thyroidal illness) complicates interpretation.
Key steps in diagnosis:
Clinical suspicion based upon history/exam.
- Thyroid hormone assays: total T4 (most commonly used), free T4, TSH, thyroglobulin autoantibodies, when indicated.
- Identify possible concurrent illnesses which could be suppressing thyroid hormone (illness, drugs).
- Certain breeds appear to be at increased risk: Golden Retriever, Doberman Pincher, Irish Setter, Miniature Schnauzer, Dachshund, Cocker Spaniel, and Airedale Terrier.
- A recent incidence study (2025) indicated that hypothyroidism remains a prevalent endocrinopathy in dogs and evaluated complications and treatment response (PMC)
- A retrospective study of dyslipidemia (2025) also noted data indicating that dogs with hypothyroidism had significant increases in serum cholesterol (Huang et al., 2025).
Care & Management
- Thyroid hormone replacement (levothyroxine) for life is the usual standard of care. Regular monitoring of clinical signs and bloodwork is needed.
- Diet and weight management are critical as metabolism and weight gain are affected.
- Also, because of developing dermatological changes and possible secondary infections, skin/coat care (bathing, pyoderma management) will be necessary.
- Regular re-evaluation of dosing and lab values is warranted as changes to therapy may be necessary along the way.
Recent/Unique Findings
An evaluation in a metabolomic profiling study (2022) produced measurable metabolic shifts in dogs with low thyroxine.
3. Canine Hypoadrenocorticism (Addison’s Disease)
Hypoadrenocorticism (HA) is a condition that occurs when the adrenal cortex produces too little glucocorticoids (cortisol) and/or mineralocorticoids (aldosterone). In dogs, the most common form of HA is primary (idiopathic or immune-mediated destruction of the cortex) (Laura Van Vertloo, 2024).
Clinical Signs
The clinical signs of HA are often vague and non-specific (hence the term “the great imitator” commonly used in veterinary references) because adrenal hormones affect electrolyte balance, volume status, immune function and metabolism.
Lethargy, anorexia, vomiting and diarrhoea
In “typical” HA: hyponatremia; hyperkalemia; hypovolemia, which often leads to collapse or shock in an adrenal crisis.
In “atypical” HA (that is, neither classic nor electrolyte problems initially): there may be chronic signs (vomiting, diarrhoea, lethargy, hypocholesterolemia/hypoalbuminaemia).
Common comorbid stressors may trigger a crisis (such as surgery, illness).
Diagnosis
- A high index of suspicion should be employed in any dog with vague signs and electrolyte derangements (Na: K ratio is less than ~27:1, hyperkalemia).
- Testing to confirm: resting cortisol (a low resting cortisol value helps rule in) and the ACTH stimulation test is the gold standard test to confirm adrenal insufficiency.
- Some dogs with atypical HA may initially have normal electrolytes, so traditional signs confirmed with hormone testing still apply.
A recent 2022 summary and evaluation of 35+ dogs with spontaneous hypoadrenocorticism provided classification and consideration of clinicopathologic features (Guzmán Ramos et al., 2022).
Care & Management
For Emergencies (adrenal crisis), immediate IV fluids (often isotonic saline), hyperkalemia correction (e.g., calcium gluconate in arrhythmia), glucocorticoid + mineralocorticoid replacement
For Chronic Management, Maintenance hormone replacement, mineralocorticoid (e.g., DOCP monthly) + glucocorticoid (e.g., prednisone), monitor periodically, electrolytes, clinical signs, and adjust doses during stress.
Owner education is key! Educate the owner about signs of crisis, how to adjust during stress/illness, and when to consult their veterinarian. A qualitative study (2024) showed that owners of Addisonian dogs described heightened anxiety during crises and a difficult adjustment for lifetime management.
Unique/Recent Insights
The 2023 AAHA guidelines note that up to 25-30% of HA dogs may present with normal electrolytes (i.e., “atypical” HA) (AAHA, 2024).
A recent study (2025) describes a rare case of hypoadrenocorticism presenting with complete atrioventricular block due to hyperkalemia (Pașca et al., 2025).
Key Takeaway
While it is less common than other endocrine disorders, hypoadrenocorticism can be life-threatening if undiagnosed. Early suspicion, definitive diagnostics, and long-term hormone replacement allow many dogs to live comfortably managed lives.
4. Canine Diabetes Mellitus
In dogs, DM, or diabetes mellitus, is characterised by a deficiency of insulin (similar to type 1 in people), leading to hyperglycemia, glucosuria, weight loss, polyphagia, polydipsia, and polyuria.
Clinical Signs
- Drinking more than normal (polydipsia), urinating more than normal (polyuria).
- Eating more than normal (polyphagia) with the loss of weight because glucose cannot be used/in a usable form.
- Lethargy/weakness, plantigrade posture (in some cases due to neuropathy), bilateral cataracts (more common in dogs).
- Complications without treatment: dehydration, urinary tract infections, diabetic ketoacidosis (DKA) (e.g., vomiting, depressed, and ketotic/acetone odour on breath) – emergency visit to a veterinarian should be considered.
Diagnosis
- Hyperglycemia with +++ glucosuria and elevated fructosamine (indicative of average glucose level).
- In recent metabolomics studies, dogs with high fructosamine levels demonstrated considerable changes in metabolites using NMR analysis.
- Rule out secondary causes of hyperglycemia (e.g., pancreatitis or other infections).
Management
- Insulin therapy (usually administered twice daily) involves the use of either intermediate or long-acting insulin, paired with a dietary plan (high fibre with scheduled feeding times) and a weight management plan.
- Monitor blood glucose curves or CGMs (monitor glucose continuously – commercially available) for insulin management (work with your veterinarian).
- Owner education and training on injection procedure and hypoglycemia, as well as tolerance of the feeding/timing schedule.
- Regularly scheduled veterinary check-up for monitoring for complications (e.g., pancreatitis, urinary tract infections, cataracts, and neuropathy).
Unique/Novel Findings
A recent summary (2023) of canine diabetes literature stresses a multifactorial aetiology in dogs (Nature.com, 2023).
The dyslipidaemia study (2025) showed dogs with diabetes mellitus have median cholesterol ~321 mg/dL and ~85% have hypercholesterolemia (Huang et al., 2025).
5. Practical Guide for Pet Owners and Veterinary Practitioners
Identifying warning signs of endocrine disease
- If your dog exhibits one or more of these clinical signs, it is reasonable to pursue an endocrine work-up:
- Unexplained weight gain or weight loss, with or without changes in appetite.
- Increased thirst and urination.
- Changes to skin and/or coat (such as alopecia, thinning, recurrent skin infections) or muscle wasting.
- Chronic gastrointestinal signs or vomiting or diarrhoea with no obvious gastrointestinal cause.
- Electrolyte imbalances or dyslipidemia on routine laboratory work.
- Older middle-aged dogs (> 5-6 years old) who experience changes in behaviour, metabolism or coat.
Diagnostic tip-sheet
Choose 3-4 core diagnostic tests and initiate:
1. History + physical exam + baseline bloodwork (CBC/ biochem/ lipids/ electrolytes/ THyroid panel if age or clinical signs warrant)
2. If you suspect thyroid disease: consider total T4, free T4, TSH, rule out “sick euthyroid”
3. If you suspect HAC: ALP + cholesterol + ALT + liver panel + screening test (either LDDST or ACTH stim) if indicated + other imaging (ultrasound or CT) if indicated.
4. If you suspect HA: electrolytes, resting cortisol, then ACTH stim if indicated.
5. If you suspect DM: fasting glucose, fructosamine, urinalysis or urinary glucose and consider CGM.
General tips for the management of your dog as an owner
Know the disease: what does this mean, what signs to watch for.
Be consistent: for example, with feeding time, monitoring, administration of medications/injections, lifestyle, etc.
Stress management: Dogs with endocrine disease (especially HA, HAC) can decompensate due to stress/illness.
| Disease | Key Hormonal Abnormality | Typical Dog Age/Breed | Key Clinical Signs | Key Diagnostic Tests | Disease |
| Hypothyroidism | ↓ Thyroxine (T4/T3) | Middle-aged, mid to large breeds | Lethargy, weight gain, alopecia, cold intolerance | Total T4, free T4, TSH, and exclusion of other illnesses | Hypothyroidism |
| Hyperadrenocorticism (HAC) | ↑ Cortisol (often pituitary-driven) | Older dogs (>6 years), small & large breeds | PU/PD, pot-belly, muscle loss, thin skin, alopecia | LDDST/ACTH stim, imaging, liver enzymes, cholesterol | Hyperadrenocorticism (HAC) |
| Hypoadrenocorticism (HA) | ↓ Cortisol ± ↓ Aldosterone | Any age but often young-middle age | Vomiting/diarrhoea, collapse/shock, hyperkalaemia | Resting cortisol, ACTH stim, electrolytes | Hypoadrenocorticism (HA) |
| Diabetes Mellitus (DM) | ↓ Insulin → ↑ blood glucose | Middle-aged dogs, sometimes small breeds | PU/PD, polyphagia + weight loss, glucosuria | Blood glucose, fructosamine, CGM | Diabetes Mellitus (DM) |
7. Conclusion
Endocrine diseases in dogs can often be subtle in nature and may mimic other diseases. However, the risk of delayed diagnosis and/or management can be grave. Being vigilant for the red flags described above, and taking advantage of diagnostic and treatment advancements (as discussed above in the context of metabolomic and dyslipidaemia research), can allow veterinarians and owners to improve outcomes and quality of life for dogs diagnosed with these disorders.
Recent guidelines from the AAHA (2023) indicate a trend towards team-based care, and that we should be using standardised algorithms and decision support for all forms of canine endocrinopathies.
Furthermore, with emerging research on muscle wasting in HAC, changes in the microbiome of animals, and lipid/metabolite profiling, it is clear that we are evolving our understanding of these conditions, and personalised care will continue to evolve.
If you suspect you have a dog with an endocrine disease, and you have a dog with a diagnosed endocrine disease and want to optimise care, seek out your veterinarian and refer to the latest guidelines and literature.
Sources
AAHA. (2024). Canine Hypoadrenocorticism (Addison’s disease). [online] Available at: https://www.aaha.org/resources/2023-aaha-selected-endocrinopathies-of-dogs-and-cats-guidelines/canine-hypoadrenocorticism-addisons-disease [Accessed 26 Oct. 2025].
Bugbee, A., Rucinsky, R., Cazabon, S., Kvitko-White, H., Lathan, P., Nichelason, A. and Rudolph, L. (2023). 2023 AAHA Selected Endocrinopathies of Dogs and Cats Guidelines. Journal of the American Animal Hospital Association, [online] 59(3), pp.113–135. doi:https://doi.org/10.5326/JAAHA-MS-7368.
Guzmán Ramos, P.J., Bennaim, M., Shiel, R.E. and Mooney, C.T., 2022. Diagnosis of canine spontaneous hypoadrenocorticism. Canine medicine and genetics, 9(1), p.6.
Heseltine, J. (2024). Hypothyroidism in Animals – Endocrine System. [online] Veterinary Manual. Available at: https://www.msdvetmanual.com/endocrine-system/the-thyroid-gland/hypothyroidism-in-animals.
Huang, W., Paulin, M.V. and Snead, E.C., (2025). Serum cholesterol disturbances in dogs with common endocrinopathies at the time of diagnosis: a retrospective study. BMC Veterinary Research, 21(1), p.138.
Laura Van Vertloo (2024) Addison Disease (Hypoadrenocorticism) in Animals. [online] MSD Veterinary Manual. Available at: https://www.msdvetmanual.com/endocrine-system/the-adrenal-glands/addison-disease-hypoadrenocorticism-in-animals.
Nature.com. (2023). Canine Diabetes Mellitus Research | Nature Research Intelligence. [online] Available at: https://www.nature.com/research-intelligence/nri-topic-summaries/canine-diabetes-mellitus-research-micro-731951? [Accessed 26 Oct. 2025].Pașca, P.M., Solcan, G., Blageanu, A., Lăcătuș, C.M., Peștean, P.C., Stancu, C.A. and Baisan, A.R., 2025. Transient Third-Degree Atrioventricular Block in a Dog with Addisonian Crisis. Veterinary Sciences, 12(1), p.63.
