Thyroid Symptoms Explained: Hypothyroidism vs Hyperthyroidism

Quick Answer

The thyroid can malfunction in two opposite ways. Hypothyroidism (underactive) slows the body down — causing weight gain, fatigue, cold intolerance, dry skin and constipation. Hyperthyroidism (overactive) speeds it up — causing weight loss, palpitations, heat intolerance, anxiety and tremors. A single TSH blood test tells the two apart and is the first step to diagnosis.

Key Takeaways

• Hypothyroidism slows metabolism; hyperthyroidism speeds it up.
• Hypothyroidism is far more common in India (~11%) and affects women 5-8× more than men.
• High TSH means underactive; low TSH means overactive.
• Most thyroid disorders are easily managed with daily medication and monitoring.
• A simple, inexpensive TSH test confirms the diagnosis — don't ignore persistent symptoms.

Thyroid disorders are among the most common endocrine conditions I see in Navi Mumbai, and they often go undiagnosed for years because symptoms build slowly. The thyroid — a butterfly-shaped gland in the front of your neck — regulates your metabolism, so when it misfires the effects show up everywhere, from heart rate to body temperature to weight.

Hypothyroidism: The Underactive Thyroid

Hypothyroidism is far more common, affecting about 11% of Indians, with women being 5-8 times more likely to develop it than men.

Common Symptoms

Metabolic Symptoms:

• Unexplained weight gain despite no change in diet
• Fatigue and lethargy, especially in the morning
• Feeling cold when others are comfortable
• Constipation

Physical Changes:

• Dry, coarse skin and hair
• Hair thinning or hair loss, particularly from the outer third of eyebrows
• Puffy face and swollen eyelids
• Brittle nails
• Hoarse voice

Neuropsychiatric Symptoms:

• Depression or low mood
• Brain fog and difficulty concentrating
• Memory problems
• Slowed thinking and speech

Other Signs:

• Heavy or irregular menstrual periods
• Muscle aches and joint pain
• Slow heart rate
• Elevated cholesterol levels

Diagnosis

Hypothyroidism is diagnosed through blood tests:

• TSH: Elevated (usually > 4.5 mIU/L)
• Free T4: Low
• Anti-TPO antibodies: May be elevated in Hashimoto's thyroiditis (autoimmune cause)

Hyperthyroidism: The Overactive Thyroid

Less common but potentially more dangerous in the short term, hyperthyroidism causes the body's systems to speed up.

Common Symptoms

Metabolic Symptoms:

• Unintentional weight loss despite normal or increased appetite
• Heat intolerance and excessive sweating
• Increased frequency of bowel movements

Cardiovascular Symptoms:

• Rapid or irregular heartbeat (palpitations)
• Tremors in hands and fingers
• High blood pressure

Neuropsychiatric Symptoms:

• Anxiety, nervousness, and irritability
• Insomnia
• Restlessness

Physical Changes:

• Fine, thinning hair
• Warm, moist skin
• Bulging eyes (in Graves' disease)
• Goiter (visible neck swelling)

Other Signs:

• Light or absent menstrual periods
• Muscle weakness, particularly in thighs
• Fatigue despite overactivity

Diagnosis

Hyperthyroidism is diagnosed through blood tests:

• TSH: Suppressed (usually < 0.3 mIU/L)
• Free T4 and Free T3: Elevated
• TSH receptor antibodies: May be present in Graves' disease

Hypothyroidism vs Hyperthyroidism: Quick Comparison

Treatment Options

Hypothyroidism Treatment

• Levothyroxine: The standard treatment is daily thyroid hormone replacement (levothyroxine sodium)
• Taken on an empty stomach, ideally 30-60 minutes before breakfast
• Dosage is individualized based on weight, age, TSH levels, and other factors
• Regular TSH monitoring (initially every 6-8 weeks, then every 6-12 months once stable)
• Most patients require lifelong treatment

Hyperthyroidism Treatment

• Anti-thyroid medications: Methimazole or carbimazole to reduce hormone production
• Beta blockers: To control heart rate and tremors while thyroid levels normalize
• Radioactive iodine therapy: Destroys overactive thyroid tissue
• Surgery (thyroidectomy): For large goiters, suspected cancer, or when other treatments fail

When to See a Doctor

If you have several of the symptoms listed above — especially if you have a family history of thyroid disease, are a woman over 30, or have been pregnant in the last year — a thyroid function test (TSH) is a simple and inexpensive blood test.

Do not ignore persistent symptoms. Early treatment prevents complications and significantly improves quality of life.

The Bottom Line

The thyroid gland may be small, but its effects on your body are profound. If you suspect a thyroid problem, the first step is a TSH blood test. With proper diagnosis and treatment, most thyroid disorders can be managed effectively, allowing you to live a normal, healthy life.

To discuss your thyroid symptoms or test results, book an appointment with Dr. Aditya Davhale, or learn more about my internal medicine services.

This article is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.