Hypothyroidism: Causes, Symptoms, and Treatment — What You Need to Know

What Is Hypothyroidism?

Hypothyroidism is a condition where the thyroid gland does not produce enough thyroid hormones (T3 and T4). The thyroid gland, a butterfly-shaped organ at the front of the neck, acts as the body’s metabolic regulator — controlling energy, temperature, heart rate, and virtually every organ system.

When thyroid hormone levels are low, the body’s processes slow down, leading to a wide range of symptoms.

Hypothyroidism is extremely common in India, affecting approximately 1 in 10 adults, with women being 5–8 times more likely to be affected than men.

What Causes Hypothyroidism?

1. Hashimoto’s Thyroiditis (Most Common)

An autoimmune condition where the immune system attacks the thyroid gland
Gradual destruction of thyroid tissue over months to years
Diagnosed by elevated Anti-TPO (thyroid peroxidase) antibodies
Often runs in families

2. Iodine Deficiency

Iodine is essential for thyroid hormone production
While iodized salt has reduced this problem in India, it still occurs in certain regions
Excessive iodine can also impair thyroid function

3. Post-Surgical or Post-Radioiodine

After thyroid surgery (thyroidectomy)
After radioactive iodine treatment for hyperthyroidism or thyroid cancer

4. Medications

Amiodarone (heart medication)
Lithium (psychiatric medication)
Immune checkpoint inhibitors (cancer therapy)

5. Central Hypothyroidism (Rare)

Due to pituitary or hypothalamic disease
TSH may be low or normal despite low thyroid hormones

6. Congenital Hypothyroidism

Present from birth
Detected by newborn screening
Requires immediate treatment to prevent developmental delays

Symptoms of Hypothyroidism

Symptoms develop gradually and are often attributed to aging or stress:

General:

Fatigue and lethargy
Weight gain (usually modest — 3–5 kg)
Cold intolerance — feeling cold when others are comfortable
Constipation

Skin and Hair:

Dry, rough skin
Hair loss and brittle hair
Puffy face, especially around the eyes
Swelling of hands and feet

Cardiovascular:

Slow heart rate (bradycardia)
Elevated cholesterol levels
Diastolic hypertension

Reproductive:

Heavy or irregular menstrual periods
Difficulty conceiving
Increased risk of miscarriage

Neurological:

Brain fog, poor concentration
Depression
Muscle aches and weakness
Carpal tunnel syndrome

Important: Many patients with mild hypothyroidism have no obvious symptoms — this is why screening is important, especially in high-risk groups.

How Is Hypothyroidism Diagnosed?

Blood Tests

Test	Purpose	Typical Finding
TSH	Primary screening test	Elevated (above 4.5–5.0 mIU/L)
Free T4	Measures active thyroid hormone	Low in overt hypothyroidism; normal in subclinical
Anti-TPO antibodies	Identifies Hashimoto’s thyroiditis	Positive in autoimmune thyroiditis
Free T3	Rarely needed for diagnosis	Usually not necessary for routine cases

Types of Hypothyroidism

Overt hypothyroidism: High TSH + Low Free T4 — always needs treatment
Subclinical hypothyroidism: High TSH + Normal Free T4 — treatment decision depends on TSH level, symptoms, antibodies, and other factors

Treatment of Hypothyroidism

Levothyroxine (LT4) — The Standard Treatment

Levothyroxine is a synthetic thyroid hormone identical to what the body naturally produces. It is:

Safe, effective, and well-tolerated
Taken as a single daily dose, usually in the morning
Available as tablets in various strengths (12.5, 25, 50, 75, 88, 100, 125, 150 mcg)

How to Take Levothyroxine Correctly

This is crucial — improper intake is the most common reason for persistent symptoms:

Take on an empty stomach — 30–60 minutes before breakfast
Take with plain water — not milk, tea, coffee, or juice
Avoid calcium and iron supplements within 4 hours of taking the tablet
Be consistent — take at the same time every day
Do not skip doses — if missed, take it as soon as remembered (but not double doses)

Monitoring and Dose Adjustment

TSH check at 6–8 weeks after starting or changing dose
Goal TSH: usually 0.5–2.5 mIU/L for most patients
In pregnancy: TSH target is < 2.5 mIU/L in the first trimester
Once stable, annual TSH monitoring is sufficient
Dose may need adjustment during pregnancy, after weight changes, or with aging

Common Myths About Hypothyroidism

Myth 1: “Thyroid causes major weight gain”

Reality: Hypothyroidism causes modest weight gain (3–5 kg), mostly water retention. Significant obesity is rarely due to thyroid alone. If you’re gaining significant weight, other causes should be explored.

Myth 2: “Once on thyroid medication, always on it”

Reality: Most patients with Hashimoto’s need lifelong treatment. However, some causes (post-partum thyroiditis, drug-induced) may be temporary. Your endocrinologist will guide you.

Myth 3: “I should avoid goitrogens (cabbage, broccoli, soy)”

Reality: Normal dietary amounts of these foods do not significantly affect thyroid function in people taking adequate levothyroxine. You don’t need to avoid them.

Myth 4: “Natural thyroid supplements are better”

Reality: Desiccated thyroid extracts and over-the-counter “thyroid support” supplements are not recommended due to inconsistent potency and potential harm.

Myth 5: “My T3 is normal, so there’s no problem”

Reality: T3 is the last hormone to drop. TSH and Free T4 are far more reliable for diagnosis and monitoring.

Hypothyroidism in Special Populations

Pregnancy

Untreated hypothyroidism increases risk of miscarriage, preeclampsia, and impaired fetal brain development
TSH should be checked before conception or as early as possible in pregnancy
Levothyroxine dose often needs to be increased by 30–50% during pregnancy
Monthly TSH monitoring during first half of pregnancy

Elderly

Symptoms may overlap with normal aging
Start with lower doses and increase gradually
Over-treatment (suppressed TSH) increases risk of atrial fibrillation and osteoporosis

Subclinical Hypothyroidism

TSH between 5–10 with normal T4
Treatment is recommended if:
- TSH > 10 mIU/L
- Positive Anti-TPO antibodies
- Symptoms present
- Planning pregnancy
- Elevated cholesterol

When to See an Endocrinologist

Difficulty achieving target TSH despite adequate levothyroxine doses
Persistent symptoms despite normal TSH
Thyroid nodules discovered alongside hypothyroidism
Hypothyroidism during pregnancy
Subclinical hypothyroidism — whether to treat or monitor
Suspected central hypothyroidism
Co-existing endocrine conditions (diabetes, adrenal insufficiency)

The Bottom Line

Hypothyroidism is a common, treatable condition. With the right dose of levothyroxine taken correctly, most patients can achieve complete symptom relief and normal thyroid function. The key is proper diagnosis, correct medication technique, and regular monitoring.

“Hypothyroidism is one of the most treatable conditions in medicine — the challenge is taking the medication correctly and consistently.”

If you suspect thyroid problems or have been diagnosed but still feel unwell, consult an endocrinologist for a thorough evaluation and optimized treatment plan.