What are the most common thyroid diseases and their treatments?

Most Common Thyroid Diseases

The most common thyroid diseases are hypothyroidism (primarily Hashimoto's thyroiditis), hyperthyroidism (primarily Graves' disease), and nodular thyroid disease, with hypothyroidism affecting up to 20% of older women and hyperthyroidism affecting approximately 0.2-1.4% of the global population. 1, 2, 3

Hypothyroidism

Prevalence and Causes

• Hashimoto's thyroiditis (chronic autoimmune thyroiditis) is the most common cause in industrialized nations 2
• Worldwide, iodine deficiency remains the most common cause 2
• Prevalence increases with age, affecting up to 20% of women over 60 years 2
• Other causes include:
  • Previous thyroid treatments (radioactive iodine, surgery)
  • Medications (amiodarone, lithium, immune checkpoint inhibitors)
  • Subacute thyroiditis (post-inflammatory phase)
  • Congenital hypothyroidism 2, 4

Clinical Presentation

• Fatigue, muscle cramps, constipation
• Cold intolerance, hair loss
• Voice changes, weight gain
• Intellectual slowness, insomnia
• If untreated, can progress to myxedema and myxedema coma 2

Diagnosis

• TSH testing is the recommended initial screening test
• Elevated TSH with normal free T4 indicates subclinical hypothyroidism
• Elevated TSH with low free T4 indicates overt hypothyroidism
• Anti-thyroid peroxidase (TPO) antibodies help confirm autoimmune etiology 2, 1

Treatment

• Levothyroxine is the standard treatment
• Initial dosing typically 75-100 μg daily for women and 100-150 μg daily for men
• Target TSH within 0.4-4.5 mIU/L for most patients
• Monitor thyroid function tests every 6-8 weeks after treatment initiation or dose changes, then every 6-12 months once stable 1

Hyperthyroidism

Prevalence and Causes

• Affects 0.2-1.4% of people worldwide (overt hyperthyroidism)
• Subclinical hyperthyroidism affects 0.7-1.4% of people worldwide
• Graves' disease is responsible for 95% of hyperthyroidism cases in pregnancy 2, 3
• Other causes include:
  • Toxic nodular goiter
  • Thyroiditis (transient thyrotoxic phase)
  • Excessive thyroid hormone intake 3, 5

Clinical Presentation

• Tremors, nervousness, insomnia
• Excessive sweating, heat intolerance
• Tachycardia, hypertension
• Goiter
• Graves' disease specifically: eyelid lag/retraction, pretibial myxedema
• Thyroid storm (rare but life-threatening) 2, 3

Diagnosis

• Suppressed TSH with elevated free T4/T3 indicates overt hyperthyroidism
• Suppressed TSH with normal free T4/T3 indicates subclinical hyperthyroidism
• TSH-receptor antibodies help diagnose Graves' disease
• Thyroid scintigraphy helps differentiate causes (increased uptake in Graves' disease and toxic nodules, decreased in thyroiditis) 2, 1, 3

Treatment

• Three main options for Graves' disease and toxic nodular goiter:
  1. Antithyroid drugs (methimazole, propylthiouracil)
  2. Radioactive iodine ablation
  3. Thyroidectomy
• Thyroiditis is managed symptomatically or with glucocorticoids 3, 5

Nodular Thyroid Disease

Prevalence and Causes

• Common endocrine abnormality
• Contributing factors include genetic abnormalities, dietary and environmental factors 6

Clinical Presentation

• Often asymptomatic
• May cause mild mechanical symptoms (feeling of fullness in throat)
• Can be associated with hyperthyroidism (toxic nodular goiter) 6

Diagnosis

• Thyroid function tests (TSH, free T3, free T4)
• Thyroid ultrasound
• Thyroid scintigraphy for functional assessment
• Fine-needle aspiration biopsy for suspicious nodules 6

Treatment

• Observation for benign, asymptomatic nodules
• Surgical removal for suspicious or symptomatic nodules
• Radioiodine therapy for toxic nodular goiter
• Minimally invasive ablation techniques 6

Subacute Thyroiditis

Characteristics

• Self-limited inflammatory disorder
• Often associated with painful swelling of the thyroid gland
• Typically progresses through phases:
  1. Initial thyrotoxic phase (due to release of stored hormones)
  2. Hypothyroid phase
  3. Recovery phase (may result in permanent hypothyroidism in up to 15% of cases) 6

Treatment

• Nonsteroidal anti-inflammatory drugs for pain relief
• Corticosteroids for severe cases
• Beta-blockers for symptomatic thyrotoxicosis
• Levothyroxine if permanent hypothyroidism develops 6

Special Considerations

Thyroid Disease in Pregnancy

• Untreated hyperthyroidism increases risk of severe preeclampsia, preterm delivery, heart failure, and possibly miscarriage 2
• Untreated hypothyroidism increases risk of preeclampsia and low birth weight 2

Thyroid Disease in Children

• Autoimmune thyroid disease occurs in 17-30% of children with type 1 diabetes 2
• Screening recommended for children with type 1 diabetes by measuring thyroid antibodies and TSH 2
• Congenital hypothyroidism requires prompt treatment to prevent neurological damage 2

Subclinical Thyroid Disease

• Subclinical hypothyroidism: 2-5% per year progress to overt hypothyroidism 2
• Subclinical hyperthyroidism: 1-2% per year with TSH <0.1 mIU/L develop overt hyperthyroidism 2
• Treatment decisions should consider age, degree of TSH abnormality, and presence of comorbidities 2, 1