Hypothyroidism in Maltese: Symptoms, Testing, Treatment

Hypothyroidism — an underactive thyroid gland leading to low circulating thyroid hormones — is a clinically important endocrine disorder in middle‑aged to senior dogs. For the Maltese, a small, long‑lived breed that commonly reaches 12–15 years, hypothyroidism most often emerges in the senior window (8–9 years and older) and may be complicated by breed‑specific age‑related problems such as [mitral valve disease](https://seniorpet.org/knowledge/cavalier-king-charles-spaniel-mitral-valve-disease "Mitral Valve Disease Guide") (MVD), luxating patella, cataracts, portosystemic shunts, [dental disease](https://seniorpet.org/knowledge/siamese-cat-dental-disease "Dental Disease in Senior Pets"), collapsed trachea, and white shaker syndrome. This article explains how hypothyroidism presents in senior Maltese, how veterinarians test for and confirm the diagnosis (and how concurrent illnesses can distort testing), best‑practice treatment and monitoring, and practical advice for owners managing a Maltese with suspect or confirmed hypothyroidism.

Why the Maltese deserves breed‑specific consideration

The Maltese is a small, predominantly white companion dog with several commonly reported health issues that intersect with thyroid disease:

• Cardiac: Mitral valve disease (MVD) is common in small breeds and can coexist with hypothyroidism.
• Orthopedic: Luxating patella and degenerative joint disease are frequent; thyroid deficiency can worsen weight gain and exercise intolerance.
• Ocular: Cataracts are seen in older Maltese; vision changes complicate activity recommendations.
• Hepatic: Portosystemic shunts (PSS) are a recognized congenital problem in small breeds and alter thyroid testing.
• Dental: Severe periodontal disease is common and contributes to systemic inflammation.
• Respiratory: Collapsed trachea increases anesthetic risk during diagnostic procedures.
• Neurologic: White shaker syndrome (generalized tremor disorder of small white breeds) can mimic neurologic signs sometimes attributed to endocrine disease.

Because these conditions often co‑occur in Maltese seniors, a careful, pragmatic diagnostic approach is essential to avoid misdiagnosis and ensure safe treatment.

What causes hypothyroidism in dogs (and Maltese)?

In dogs, hypothyroidism most commonly results from one of two mechanisms:

• Lymphocytic (immune‑mediated) thyroiditis: progressive autoimmune destruction of thyroid tissue.
• Idiopathic thyroid atrophy: gradual loss of functional thyroid tissue without a clear immune signature.

Either mechanism reduces production of thyroxine (T4) and triiodothyronine (T3), lowering metabolic rate and causing systemic signs. Breed‑specific genetic predisposition is less clear for Maltese versus other breeds, but the age at onset (middle‑aged to senior) aligns with the typical disease course.

Reference sources: Ettinger & Feldman, Textbook of Veterinary Internal Medicine; Peterson, Clinical Endocrinology of Dogs and Cats.

Clinical signs in senior Maltese: what to watch for

Hypothyroidism in dogs is a slowly progressive disease. In Maltese seniors (around 8–9 years), owners may notice subtle changes at first that progress over months:

• Hair/skin: Bilateral symmetrical alopecia (tail, trunk), thin brittle coat, failure to regrow after clipping, cold intolerance; in Maltese the typical white coat may appear dull, with recurrent skin infections (pyoderma).
• Weight: Unexplained weight gain despite normal appetite (or decreased activity).
• Activity/neuromuscular: Lethargy, exercise intolerance, stiffness, heightened tendency to sit or rest; signs may be confused with pain from luxating patella or osteoarthritis.
• Metabolic: Hypercholesterolemia (routine chemistry may show elevated cholesterol).
• Cardiac: Bradycardia or decreased exercise tolerance. While hypothyroid dogs typically do not develop primary cardiomyopathy, thyroid hormone deficiency reduces myocardial contractility — important in MVD‑affected Maltese.
• Neurologic: Peripheral neuropathy leading to weakness, delayed proprioception; myopathy can cause a stiff gait. Note: high‑frequency tremors of white shaker syndrome are distinct (see below).
• Reproduction/dermatologic: Hyperpigmentation, seborrhea, rat‑tail appearance.
• Less common: Behavioral changes (depression), decreased cognitive engagement, heat seeking.

Because many of these signs overlap with other Maltese age‑related conditions (e.g., dental pain causing lethargy; white shaker syndrome causing tremors; PSS causing lethargy and GI signs), a methodical diagnostic plan is required.

Distinguishing hypothyroidism from look‑alikes in Maltese

• White shaker syndrome: Presents with generalized high‑frequency tremors, often abrupt, and responds to corticosteroids. Hypothyroid neuromuscular signs are usually weakness and stiff gait rather than tremor. Concurrent testing and neurologic exam differentiate the two.
• Portosystemic shunt (PSS): PSS can cause poor growth, neurologic signs (hepatic encephalopathy), and abnormal liver enzymes. Liver dysfunction and systemic illness can lower total T4 (the "euthyroid sick" effect) and confound thyroid testing.
• Non‑thyroidal illness (NTI) / Euthyroid sick syndrome: Any systemic disease (including dental infection, [heart disease](https://seniorpet.org/knowledge/cavalier-king-charles-spaniel-mitral-valve-disease "Heart Disease in Senior Pets"), liver disease) can suppress TT4 without true hypothyroidism. Free T4 by equilibrium dialysis and measurement of canine TSH help distinguish NTI from true primary hypothyroidism.
• Age‑related degenerative joint disease / luxating patella: Reduced activity and stiffness could be orthopedic rather than endocrine; orthopedic exam and radiographs help.

Testing strategy: what to request and why

Because of euthyroid sick syndrome and breed‑specific comorbidities in Maltese, a layered approach is recommended.

Baseline bloodwork

- CBC and chemistry panel (evaluate liver values, albumin, cholestatic enzymes, cholesterol). - Urinalysis.

Thyroid testing (interpret in clinical context)

- Total T4 (TT4): a good screening test but reduced by NTI and drugs. - Free T4 by equilibrium dialysis (fT4 ED): less affected by binding protein changes and NTI — more specific. - Canine TSH (cTSH): high in primary hypothyroidism; however, low sensitivity (some hypothyroid dogs have normal TSH early). - Anti‑thyroglobulin autoantibodies (TgAA): presence supports autoimmune thyroiditis, though absence does not rule it out.

Additional useful tests

- Baseline cholesterol (often elevated in hypothyroidism). - Urine cortisol (to rule out hypoadrenocorticism if clinical suspicion). - Imaging: thoracic radiographs if MVD/cardiac disease suspected; abdominal ultrasound if PSS suspected.

Interpretation caveats for Maltese:

- Liver disease (PSS) or systemic infection can reduce TT4 — send fT4 ED and cTSH if TT4 low. - Recent glucocorticoid or nonsteroidal therapy can influence results. Note any medications (e.g., sulfonamides lower TT4). - If the dog is in poor general health, stabilize and retest thyroid assays later.

Example laboratory data and typical interpretation (reference ranges vary by lab):

| Test | Typical canine reference range* | Interpretation if low/high | |---|---:|---| | Total T4 (TT4) | ~1.0–4.0 µg/dL | Low in hypothyroid and sick dogs; high rare (hyperthyroid rare in dogs) | | Free T4 (equilibrium dialysis) | lab‑specific, less affected by illness | Low fT4 + high cTSH supports primary hypothyroidism | | Canine TSH (cTSH) | low in normal; high in primary hypothyroidism | High cTSH with low TT4/fT4 suggests primary hypothyroidism | | Anti‑thyroglobulin Ab (TgAA) | Negative/Positive | Positive suggests autoimmune thyroiditis | | Cholesterol | <300 mg/dL (lab dependent) | Often elevated in hypothyroidism |

*Always use lab‑specific reference ranges.

References: Ettinger & Feldman; published diagnostic reviews on canine hypothyroidism.

Confirming the diagnosis

A diagnosis of primary hypothyroidism is typically made when:

• Consistent clinical signs are present in a middle‑aged/older Maltese, AND
• Low TT4 and low fT4 (ED) with a high cTSH, and/or
• Presence of anti‑thyroglobulin antibodies supporting autoimmune thyroiditis.

If tests are equivocal (e.g., low TT4 but normal fT4 and cTSH), consider repeat testing after resolving concurrent illness or perform serial monitoring. Longitudinal clinical response to appropriate levothyroxine therapy (improvement in coat, energy, and cholesterol) also supports the diagnosis, but therapy should not be used as a diagnostic trial without careful monitoring and appropriate testing.

Treatment: levothyroxine (L‑thyroxine) therapy and practical dosing

Levothyroxine sodium is the treatment of choice. Key principles for Maltese seniors:

• Typical starting dose: 0.01–0.02 mg/kg PO every 12 hours (i.e., 10–20 µg/kg q12h). For a typical adult Maltese (3–4 kg), this often equates to 25 µg to 50 µg twice daily.
• Divide the total daily dose into two administrations (q12h) to mimic physiologic levels and avoid peaks/troughs.
• Administer on an empty stomach if possible (owners commonly give just before feeding).
• Monitor clinical response (coat, energy, weight, cholesterol) and laboratory levels.

Monitoring schedule:

• Recheck total T4 (ideally 4–6 hours post‑pill to detect peak) and clinical exam 4–6 weeks after starting therapy. Aim for T4 in the mid to upper half of the laboratory reference range and improvement in signs.
• Recheck again at 3 months and then every 6–12 months once stable.
• Monitor for signs of overdosage (restlessness, polyuria/polydipsia, tachycardia) — reduce dose if suspected.
• In Maltese with MVD, obtain baseline cardiac auscultation and consider follow‑up echocardiography as clinically indicated, because restoring normal thyroid hormone increases metabolic and cardiac workload.

Drug interactions and cautions:

• Certain drugs alter thyroid assays and therapy (e.g., sulfonamides, phenobarbital, glucocorticoids). Discuss all medications with your veterinarian.
• Avoid initiating thyroid therapy without assessing major cardiac disease: in severe congestive heart failure, correction of hypothyroidism can exacerbate signs; begin at lower dose and monitor closely.
• In dogs with PSS or significant hepatic dysfunction, absorption/metabolism of thyroid hormone may be altered; close monitoring and possible dose adjustments are required.

References: Peterson ME; Ettinger & Feldman; common veterinary pharmacology recommendations.

Follow‑up and monitoring: what to expect

• Clinical improvement timeline: energy and activity often improve within 2–6 weeks; coat and skin changes may take 8–12 weeks or longer.
• Cholesterol usually declines within 6–10 weeks of effective therapy.
• If no clinical or biochemical improvement after 8–12 weeks at an appropriate dose, reassess: compliance, correct dosing (peak vs. trough sampling), concurrent disease (NTI), or misdiagnosis.
• Life‑long therapy is typical. Sudden withdrawal is not recommended; long‑term monitoring is required.

How hypothyroidism interacts with Maltese comorbidities

• Mitral Valve Disease (MVD): Thyroid hormone increases myocardial contractility and heart rate. In a Maltese with MVD, initiate therapy cautiously; monitor for signs of worsening cardiac disease. Consult with your veterinarian or a cardiologist if advanced MVD is present.
• Luxating patella / osteoarthritis: Hypothyroid dogs commonly gain weight; weight loss and restored activity after therapy often improve orthopedic symptoms. Consider joint supplements, controlled exercise, and low‑impact activity.
• Cataracts: Thyroid therapy will not reverse cataracts. Coordinate with a veterinary ophthalmologist for diagnosis and possible surgery; be aware of anesthesia risks if MVD or collapsed trachea are present.
• Portosystemic shunt (PSS): PSS and chronic liver disease lower TT4 independent of thyroid status. Prefer free T4 (equilibrium dialysis) and cTSH for diagnosis. If PSS is corrected surgically, re‑evaluate thyroid function post‑correction.
• Dental disease: Systemic inflammation from periodontal disease can complicate systemic testing and the dog's overall health. Improve dental hygiene prior to or in parallel with endocrine diagnostics. Dental procedures require careful anesthetic planning in dogs with MVD or collapsed trachea.
• Collapsed trachea: Sedation and anesthesia for diagnostics or dental work require experienced handling; pre‑oxygenation and cough suppression strategies can reduce risk.
• White shaker syndrome: Tremors due to white shaker syndrome respond to corticosteroids or other immunomodulatory therapy; tremor quality and acute onset help differentiate from hypothyroid neuromuscular disease.

Practical, actionable advice for owners

Watch for early signs: in an 8–9 year old Maltese, report persistent coat thinning, unexplained weight gain, lethargy, cold intolerance, stiffness, or recurrent skin infections to your veterinarian.

Request comprehensive testing: insist on TT4, fT4 by equilibrium dialysis, and cTSH (and baseline CBC/chemistry, including cholesterol) if hypothyroidism is suspected. Ask about anti‑thyroglobulin antibodies if immune disease is a concern.

Prepare for sample timing and medications:

- Tell your clinic about all current medications and supplements (they can affect results). - If your Maltese is on antibiotics like sulfonamides, phenobarbital, or glucocorticoids, discuss timing of testing with your vet.

Start therapy correctly: if levothyroxine is prescribed, give exactly as directed (usually twice daily on an empty stomach). Keep a dosing calendar and watch for signs of overmedication.

Coordinate comorbidity care: before elective dental procedures or anesthesia, ensure MVD/cardiac status is assessed. Share thyroid status with your dentist, cardiologist, and ophthalmologist.

Diet, weight and grooming: implement a weight‑control plan (low‑calorie, high‑quality protein diet), daily tooth care to reduce periodontal disease, and regular grooming to monitor coat and skin changes.

Emergency signs: seek immediate care for new or worsening breathing difficulty (collapsed trachea/emergent heart failure), syncope, severe tachycardia, or sudden neurologic signs.

Case example (typical Maltese senior)

An 8.5‑year‑old neutered male Maltese with a history of progressive lethargy, mild weight gain, patchy hair loss along the trunk, and recurrent ear infections. Baseline chemistry shows hypercholesterolemia (420 mg/dL), normal liver enzymes, and TT4 of 0.6 µg/dL (below lab RI). Free T4 by equilibrium dialysis is low and cTSH is high. Diagnosis: primary hypothyroidism. Start levothyroxine at 0.015 mg/kg PO q12h, recheck TT4 at 4–6 weeks (peak sample) and again at 3 months; expect improved energy and coat by 8–12 weeks and normalized cholesterol within 2 months.

When to refer

• Ambiguous diagnostic results (low TT4 but normal fT4/cTSH) — consider endocrinology referral.
• Complex comorbidity: severe MVD, poorly controlled collapsing trachea, planned anesthesia, or possible PSS — refer to cardiology, surgery, or internal medicine as appropriate.
• Unresponsive cases: after adequate therapy and monitoring, if there is limited improvement, consult a veterinary internal medicine specialist.

Research and evidence base (selected)

• Ettinger SJ, Feldman EC. Textbook of Veterinary Internal Medicine (multiple editions) — authoritative guidance on endocrine disease.
• Peterson ME. Clinical Endocrinology of Dogs and Cats — practical diagnostic and therapeutic recommendations for hypothyroidism.
• Panciera DL. Canine hypothyroidism: clinical features, diagnosis and therapy — review of case series highlighting typical presentations and laboratory patterns.

(Note: clinical practice guidelines and diagnostic approaches are based on peer‑reviewed veterinary endocrinology texts and case series. Owners should discuss specific references and local laboratory references with their veterinarian.)

Final notes

Hypothyroidism is a treatable, often slowly progressive disease that commonly presents in Maltese seniors. Because many age‑related conditions in Maltese overlap with hypothyroid signs, precise testing (including fT4 by equilibrium dialysis and cTSH) and careful interpretation alongside evaluation for MVD, PSS, dental disease, and other comorbidities are essential. Most dogs respond well to oral levothyroxine with substantial improvement in [quality of life](https://seniorpet.org/knowledge/siamese-cat-quality-of-life "Quality of Life Assessment") when properly diagnosed and monitored.

If you suspect hypothyroidism in your Maltese, make an appointment with your veterinarian for a structured diagnostic plan — early detection and a coordinated approach to comorbidities will give your Maltese the best chance at a comfortable senior life.