Hypothyroidism

Overview

Hypothyroidism is a common endocrine disorder in which the thyroid gland doesn't produce enough thyroid hormones to meet the body's needs. The thyroid, a small butterfly-shaped gland in the front of your neck, produces hormones that regulate metabolism—how your body uses energy. When thyroid hormone levels are too low, the body's processes slow down.

Hypothyroidism affects millions of people worldwide, with women being five to eight times more likely to develop the condition than men. In the United States, about 5% of the population has hypothyroidism, with many more having subclinical (mild) forms. The condition becomes more common with age, affecting about 10% of women and 6% of men over age 65.

The good news is that hypothyroidism is easily diagnosed with blood tests and effectively treated with daily thyroid hormone replacement medication. Once properly treated, most people with hypothyroidism can lead completely normal lives. However, because symptoms develop gradually and can be subtle, many cases go undiagnosed for years, making awareness and regular screening important.

Types of Hypothyroidism

Symptoms

Hypothyroidism symptoms develop slowly, often over years, and can be mistaken for normal aging or other conditions:

Common Symptoms

Physical Symptoms

• Cold intolerance: Feeling cold when others are comfortable
• Dry skin: Coarse, dry, and sometimes yellowish skin
• Hair changes: Thinning hair, brittle nails
• Puffy face: Especially around the eyes
• Hoarse voice: Due to thyroid swelling
• Slow heart rate: Bradycardia
• Constipation: Due to slowed digestion
• Heavy menstrual periods: In women

Mental and Emotional Symptoms

• Depression: Feeling sad or hopeless
• Memory problems: Difficulty concentrating
• Mental sluggishness: "Brain fog"
• Irritability: Mood changes

Severe Symptoms (Myxedema)

Untreated severe hypothyroidism can lead to myxedema, a life-threatening condition:

• Extreme cold intolerance
• Drowsiness followed by profound lethargy
• Unconsciousness
• Low body temperature
• Slow breathing
• Low blood pressure

Causes and Risk Factors

Several conditions and factors can lead to hypothyroidism:

Common Causes

Autoimmune Disease

• Hashimoto's thyroiditis: Most common cause in developed countries
• Immune system mistakenly attacks thyroid tissue
• Gradual destruction of thyroid cells
• Often runs in families

Medical Treatments

• Thyroid surgery: Partial or total thyroidectomy
• Radioactive iodine: Treatment for hyperthyroidism
• Radiation therapy: To head and neck cancers
• Medications: Lithium, amiodarone, interferon alpha

Other Causes

• Congenital defects: Born without or with defective thyroid
• Pituitary disorders: Affecting TSH production
• Pregnancy: Postpartum thyroiditis
• Iodine imbalance: Too little or too much iodine
• Thyroiditis: Inflammation of the thyroid

Risk Factors

Demographics

• Gender: Women 5-8 times more likely
• Age: Risk increases after age 60
• Family history: Genetic predisposition
• Race: Higher in Caucasians and Asians

Medical History

• Previous thyroid problems
• Autoimmune diseases (Type 1 diabetes, rheumatoid arthritis)
• Down syndrome or Turner syndrome
• Bipolar disorder (lithium treatment)
• Heart disease (amiodarone treatment)

Other Risk Factors

• Pregnancy or recent delivery
• Radiation exposure
• Neck surgery
• Certain viral infections

Diagnosis

Hypothyroidism is diagnosed through blood tests that measure thyroid function:

Primary Tests

Additional Tests

Screening Recommendations

• Women over 35: Every 5 years
• Pregnant women: Early in pregnancy
• Newborns: Universal screening
• High-risk individuals: More frequent testing
• Symptoms present: Test regardless of age

Treatment

Hypothyroidism is treated with daily thyroid hormone replacement therapy:

Standard Treatment

Dosage Considerations

• Starting dose: Based on age, weight, and severity
• Young adults: 1.6 mcg/kg body weight
• Elderly: Start low (25-50 mcg) and increase slowly
• Pregnancy: Dose often needs to increase
• Heart disease: Careful dose titration

Alternative Treatments

Monitoring Treatment

• Initial monitoring: TSH every 6-8 weeks until stable
• Stable patients: Annual TSH testing
• Dose adjustments: Based on TSH levels and symptoms
• Target TSH: Usually 0.5-2.5 mIU/L
• Pregnancy: More frequent monitoring

Important Interactions

• Iron supplements: Take 4 hours apart
• Calcium supplements: Take 4 hours apart
• Antacids: Can interfere with absorption
• Soy products: May affect absorption
• Coffee: Wait 30-60 minutes after medication

Living With Hypothyroidism

With proper treatment, most people with hypothyroidism lead normal, healthy lives. Key aspects of management include:

Medication Management

• Consistency: Take medication at same time daily
• Don't skip doses: Set reminders if needed
• Storage: Keep medication away from heat and moisture
• Travel: Bring extra medication
• Brand consistency: Avoid switching brands without monitoring

Lifestyle Factors

• Regular exercise: Helps with energy and weight management
• Healthy diet: Focus on whole foods, adequate iodine
• Stress management: Stress can affect thyroid function
• Adequate sleep: 7-9 hours nightly
• Weight management: May be challenging but important

Dietary Considerations

• Iodine: Adequate but not excessive (iodized salt usually sufficient)
• Selenium: Supports thyroid function (Brazil nuts, seafood)
• Limit goitrogens: Raw cruciferous vegetables in moderation
• Soy products: May interfere with hormone absorption
• Gluten: Consider testing for celiac disease if Hashimoto's

Regular Monitoring

• Annual check-ups: Even when feeling well
• Blood tests: TSH and sometimes Free T4
• Symptom tracking: Note any changes
• Other health screening: Cholesterol, bone density
• Medication review: Check for interactions

Prevention

While many causes of hypothyroidism cannot be prevented, some measures may help reduce risk or catch it early:

Preventive Measures

• Adequate iodine: Use iodized salt if in deficient area
• Avoid excess iodine: Can trigger thyroid problems
• Radiation protection: Shield thyroid during X-rays
• Medication awareness: Know which drugs affect thyroid
• Regular screening: If at high risk

Early Detection

• Know symptoms: Don't dismiss as normal aging
• Family history: Inform healthcare providers
• Pregnancy planning: Test thyroid function
• Postpartum monitoring: Watch for thyroiditis
• Regular check-ups: Include thyroid assessment

Complications

Untreated or inadequately treated hypothyroidism can lead to serious health problems:

Special Populations

Pregnancy and Hypothyroidism

• Increased needs: Thyroid hormone requirement increases 30-50%
• Early testing: Check TSH as soon as pregnancy confirmed
• Frequent monitoring: Every 4-6 weeks in first half
• Fetal development: Critical for baby's brain development
• Postpartum: Return to pre-pregnancy dose

Children and Adolescents

• Growth effects: Can cause delayed growth and development
• School performance: May affect learning
• Puberty: Can delay sexual development
• Higher doses: Children need more per body weight

Elderly Patients

• Subtle symptoms: Often attributed to aging
• Start low: Begin with lower doses
• Cardiac risk: Monitor heart function
• Drug interactions: More common with multiple medications

Related Conditions

Hypothyroidism often occurs with other conditions, particularly autoimmune disorders: