Thyroid disorders affect approximately 2 million people in the United Kingdom, with many cases remaining undiagnosed, according to the British Thyroid Foundation. The thyroid gland plays a crucial role in regulating metabolism, growth, and energy production. The NHS identifies the two main categories of thyroid dysfunction as hypothyroidism (underactive thyroid) and hyperthyroidism (overactive thyroid). Proper diagnosis and management of these conditions are essential to prevent systemic complications and maintain overall health.
Thyroid Anatomy and Function
The thyroid gland is a butterfly-shaped endocrine organ located in the front of the neck. It produces two primary hormones:
- Thyroxine (T4): Contains four iodine atoms; the main storage form
- Triiodothyronine (T3): Contains three iodine atoms; the active form
The hypothalamic-pituitary-thyroid axis regulates hormone production:
- Hypothalamus releases thyrotropin-releasing hormone (TRH)
- Pituitary gland releases thyroid-stimulating hormone (TSH)
- Thyroid gland produces T4 and T3
Feedback loops maintain hormone balance. Peripheral conversion of T4 to T3 occurs in the liver, kidneys, and other tissues, ensuring adequate levels of active hormone.
Hypothyroidism: Underactive Thyroid
Causes and Risk Factors
Primary Hypothyroidism:
- Autoimmune thyroiditis (Hashimoto’s disease): Most common cause in the UK
- Iodine deficiency: Rare in the UK due to iodised salt
- Thyroidectomy: Partial or total removal of the gland
- Radioiodine therapy: Used for hyperthyroidism treatment
- Medications: Amiodarone, lithium
- Congenital hypothyroidism: Detected via newborn screening
Secondary Hypothyroidism:
- Pituitary or hypothalamic disease: Tumors or trauma affecting TSH or TRH production
Risk Factors:
- Female sex (5-8 times higher risk)
- Age over 60
- Family history of autoimmune disease
- Down syndrome and other genetic conditions
- History of head or neck radiation
Symptoms of Hypothyroidism
General Symptoms:
- Fatigue and lethargy
- Cold intolerance
- Weight gain despite normal appetite
- Dry skin and hair
- Constipation
- Muscle aches and weakness
Cardiovascular:
- Bradycardia (slow heart rate)
- Elevated cholesterol levels
- Hypertension (diastolic)
Neurological and Psychiatric:
- Depression and cognitive slowing
- Memory impairment
- Carpal tunnel syndrome
- Peripheral neuropathy
Reproductive:
- Menorrhagia (heavy menstrual bleeding)
- Infertility
- Delayed puberty in children
Diagnosis and Monitoring
Laboratory Tests:
- TSH: Elevated in primary hypothyroidism
- Free T4: Low in overt hypothyroidism
- Free T3: Occasionally measured
- Thyroid peroxidase antibodies (TPOAb): Positive in autoimmune thyroiditis
Additional Tests:
- Lipid profile: Check cholesterol levels
- Liver function: Monitor for medication side effects
- Cardiac evaluation: In older patients or those with comorbidities
Monitoring:
- TSH: Every 6-8 weeks until stable, then annually
- Adjust levothyroxine dose based on TSH and symptoms
Management of Hypothyroidism
Levothyroxine Replacement:
- Synthetic T4; starting dose 25-50 mcg daily in older or cardiac patients
- Typical full dose 1.6 mcg/kg/day, taken on empty stomach
- Monitor TSH for dose adjustment
Alternative Therapies:
- Liothyronine (T3): Occasionally added for persistent symptoms
- Combination therapy: T4 and T3, limited evidence for benefit
Lifestyle and Support:
- Regular monitoring and dose adjustments
- Consistent medication adherence
- Nutritional support: Adequate iodine and selenium
- Exercise to combat fatigue and weight gain
Hyperthyroidism: Overactive Thyroid
Causes and Risk Factors
Primary Hyperthyroidism:
- Graves’ disease: Autoimmune stimulation of TSH receptor; most common cause
- Toxic multinodular goitre: Autonomously functioning thyroid nodules
- Thyroiditis: Inflammatory damage causing hormone release
- Toxic adenoma: Single overactive thyroid nodule
- Excess iodine intake: Rare
Secondary Hyperthyroidism:
- Rare; pituitary adenomas producing TSH
Risk Factors:
- Female sex (estrogen influences immune response)
- Family history of thyroid autoimmune disease
- Smoking (increases risk of Graves’ ophthalmopathy)
- Stress and infection can trigger thyroiditis
Symptoms of Hyperthyroidism
General Symptoms:
- Weight loss despite increased appetite
- Heat intolerance and excessive sweating
- Nervousness, irritability, anxiety
- Tremor, palpitations, tachycardia
- Muscle weakness and fatigue
Ophthalmopathy (Graves’ disease):
- Exophthalmos (eye bulging)
- Periorbital oedema
- Diplopia (double vision)
- Corneal exposure and dryness
Cardiovascular:
- Atrial fibrillation
- Increased systolic blood pressure
- High-output heart failure in severe cases
Gastrointestinal:
- Frequent bowel movements or diarrhoea
Reproductive:
- Menstrual irregularities
- Reduced fertility
Diagnosis and Monitoring
Laboratory Tests:
- TSH: Suppressed in primary hyperthyroidism
- Free T4 and Free T3: Elevated
- TSH receptor antibodies: Positive in Graves’ disease
- Thyroid peroxidase antibodies (TPOAb): May be positive
Imaging:
- Radioactive iodine uptake scan: Differentiates causes
- Thyroid ultrasound: Evaluates nodules and goitre
Monitoring:
- TSH, Free T4 every 6-8 weeks during treatment
- Monitor for medication side effects
Management of Hyperthyroidism
Anti-thyroid Medications:
- Carbimazole: Starting dose 15-60 mg daily
- Propylthiouracil (PTU): Alternative; risk of liver toxicity
- Duration: 12-18 months, with trial withdrawal to assess remission
Definitive Treatments:
- Radioactive iodine: Destroys overactive thyroid tissue
- Surgery (thyroidectomy): For large goitres, nodules, or intolerance to other treatments
Symptomatic Management:
- Beta-blockers (propranolol): Control tremor and tachycardia
- Eyedrops or surgery: For severe ophthalmopathy
Special Populations and Considerations
Pregnancy and Thyroid Function:
- Hypothyroidism: Increase levothyroxine dose by 20-30% in first trimester
- Hyperthyroidism: PTU preferred in first trimester, carbimazole thereafter
- Regular monitoring every 4 weeks
Elderly Patients:
- Symptoms may be subtle or atypical
- Lower thresholds for treatment due to cardiac risk
- Start levothyroxine at low dose (25 mcg daily)
Paediatric Considerations:
- Congenital hypothyroidism detected via newborn screening
- Dosage weight-based; close monitoring critical
- Graves’ disease less common but more severe
Living with Thyroid Disorders
Self-Management Strategies:
- Consistent medication adherence
- Regular monitoring and blood tests
- Awareness of symptom changes
- Nutritional support: Adequate iodine intake
Support Resources:
- British Thyroid Foundation: 01252 314 643
- NHS Thyroid Information: Reliable patient information
- Endocrine Society: Professional guidelines
Quality of Life Considerations:
- Address mood and cognitive symptoms
- Support groups and counselling available
- Workplace and school accommodations for fatigue and concentration issues
Future Directions in Thyroid Care
Emerging Research:
- New immunomodulatory therapies for autoimmune thyroid disease
- Genetic markers for personalised treatment
- Novel drug delivery systems
- Improved diagnostics for subclinical thyroid dysfunction
Precision Medicine:
- Stratifying patients by genetic and immunological profiles
- Tailoring treatment to individual risk and response
- Minimising overtreatment and side effects
Conclusion
Thyroid disorders are common but treatable conditions that significantly impact metabolism, growth, and overall health. Early diagnosis through appropriate screening and laboratory tests, combined with evidence-based treatment strategies, enables effective management of both hypothyroidism and hyperthyroidism.
Patient education, consistent medication adherence, and regular monitoring are essential for maintaining hormone balance and minimising complications. Resources from organisations like the British Thyroid Foundation and the NHS provide valuable support and information.
Remember that thyroid health affects virtually every body system—maintaining hormone balance is crucial for long-term wellbeing, energy, and quality of life.
