When we think about thyroid issues in cats, hyperthyroidism (an overactive thyroid) usually comes to mind. But what about the opposite?

While rare, hypothyroidism in cats – when the thyroid gland doesn’t produce enough hormones – can quietly affect your kitty’s metabolism, energy levels, coat quality, and overall vitality.

Let’s walk through what it is, why it happens, and how to support your cat safely and naturally, while respecting that cats are wonderfully unique (and not small dogs!).

What is Hypothyroidism in Cats?

The thyroid gland produces hormones (primarily T4 and T3) that regulate:

• Metabolism
• Body temperature
• Heart rate
• Energy production
• Skin and coat health
• Growth and development

When thyroid hormone levels are too low, everything in the body can slow down.

Unlike dogs, naturally occurring hypothyroidism in adult cats is very uncommon. When it does occur, there is usually an identifiable cause.

Slow, Subtle Signs

Because thyroid hormones influence metabolism, a slowdown can show up in subtle ways:

• Weight gain despite normal appetite
• Lethargy or decreased activity
• Cold intolerance
• Dull, thinning, or poorly groomed coat
• Excess shedding or matting
• Constipation
• Slower heart rate
• Mental dullness

In kittens with congenital hypothyroidism, you may also see:

• Stunted growth
• Delayed tooth eruption
• Short limbs or disproportionate features

If your cat seems “off,” bloodwork is essential. Thyroid testing must be interpreted carefully, because illness alone can temporarily lower thyroid values.

What Causes Hypothyroidism in Cats?

Hypothyroidism in cats usually happens for a specific reason.

1. Congenital Hypothyroidism (Present at Birth)

Some kittens are born with underdeveloped or absent thyroid glands. Because thyroid hormone is essential for growth and brain development, early diagnosis is critical.

These kittens may show:

• Poor growth
• Lethargy
• Developmental delays

With proper treatment, many can improve significantly.

2. Iatrogenic Hypothyroidism (Most Common in Adults)

This is the most common cause in adult cats. “Iatrogenic” means it results from medical treatment.

Cats treated for hyperthyroidism — through:

• Radioactive iodine therapy
• Surgical thyroid removal
• Anti-thyroid medication

— may develop hypothyroidism if too much thyroid tissue is suppressed or removed.

Sometimes this is temporary. Other times, thyroid hormone replacement is needed long-term.

3. Secondary (Central) Hypothyroidism

In very rare cases, the issue originates in the pituitary gland, which signals the thyroid to produce hormones. If that signalling fails, thyroid levels can drop.

4. Severe or Chronic Illness

Systemic illness can suppress thyroid hormone levels temporarily. This is called euthyroid sick syndrome and is not true hypothyroidism.

This is why diagnosis must never rely on numbers alone – your veterinarian must interpret labs alongside clinical signs.

[RELATED] Hypothyroidism in Dogs: How to Support Thyroid Health

Natural and Holistic Management

Cats are metabolically unique. Many herbs and supplements commonly used in dogs are not safe for cats.

Holistic support focuses on strengthening the entire system while maintaining proper thyroid balance.

1. Feed a Species-Appropriate, Highly Digestible Diet

Thyroid hormones regulate metabolism. When levels are low, digestion and calorie utilization may slow.

Support your cat with:

• High-quality animal protein
• Moisture-rich foods (raw or canned)
• Minimal carbohydrates
• Balanced micronutrients

Avoid:

• Kelp or seaweed supplementation
• Iodine drops or thyroid “boosters”
• Unbalanced homemade diets

Cats are extremely sensitive to iodine levels. Improper supplementation can destabilize thyroid function.

2. Support Gut Health

The gut plays a key role in:

• Nutrient absorption
• Immune regulation
• Hormone metabolism

Use feline-specific probiotic formulas. Digestive enzymes formulated specifically for cats may also help if digestion is sluggish. A healthy gut supports better energy, coat quality, and resilience.

3. Maintain Lean Body Weight

Hypothyroid cats may gain weight more easily.

Extra weight strains:

• Joints
• The heart
• Insulin sensitivity

Gentle portion control and daily interactive play can stimulate metabolism safely. Even 5–10 minutes of wand toy play per day supports circulation and muscle tone.

4. Provide Warmth & Comfort

Cats with low thyroid function may feel colder.

Simple support includes:

• Heated (pet-safe) beds
• Extra blankets
• Sunny resting areas

Thermal comfort reduces metabolic stress and conserves energy.

5. Reduce Environmental Stress

The endocrine system is deeply connected to the nervous system. Chronic stress can disrupt hormonal signaling.

Support calm balance with:

• Predictable routines
• Consistent feeding times
• Vertical climbing spaces
• Safe hiding areas

Feline-safe calming options may include:

• L-theanine (cat-formulated only)
• Colostrum (species-appropriate dosing)
• Synthetic feline pheromone diffusers

Avoid essential oil diffusers – cats lack certain liver enzymes and are much more sensitive than dogs.

6. Support Cellular Energy (With Veterinary Guidance)

Thyroid hormones regulate mitochondrial energy production.

Under veterinary supervision, supportive nutrients may include:

• CoQ10 (cat-appropriate dose only)
• B-complex vitamins
• Taurine (essential for cats – should already be present in balanced diets)

7. Monitor – Don’t Guess

Holistic care should always be paired with:

• Regular thyroid panels
• Clinical monitoring
• Careful dose adjustments if on medication

Over-supplementation can cause serious problems. The goal is balance – not stimulation.

A Whole-Cat Perspective

Hypothyroidism in cats is uncommon, but also manageable.

Supporting the thyroid means supporting:

• Metabolism
• Energy production
• Coat quality
• Emotional balance
• Overall vitality

The goal isn’t just “normal lab numbers.” It’s a cat who feels warm, curious, comfortable, and engaged in life.

When we nourish the whole body – through species-appropriate nutrition, stress reduction, digestive support, and thoughtful monitoring – we create the conditions for true resilience. And that’s what holistic care is really about.