Thyroid Gland Disorders

The thyroid gland is a small, butterfly-shaped organ located in the front of the neck, responsible for producing hormones that regulate metabolism, growth, and development. Disorders of the thyroid gland can lead to either excessive hormone production (hyperthyroidism), reduced hormone production (hypothyroidism), or structural abnormalities like goitre and nodules. These conditions can have widespread effects on physical and mental health.

Causes

Thyroid disorders may be caused by various factors:

• Autoimmune diseases (e.g., Hashimoto’s thyroiditis, Graves’ disease)
• Iodine deficiency or excess
• Thyroid surgery or radioiodine therapy
• Congenital defects or genetic predisposition
• Thyroid nodules or tumours
• Certain medications such as lithium or amiodarone
• Infections (e.g., subacute thyroiditis)

Pathophysiology

In hypothyroidism, there is a deficiency of thyroid hormones (T3 and T4), often due to autoimmune destruction of the thyroid gland or iodine deficiency. The pituitary gland responds by increasing TSH (thyroid-stimulating hormone) to stimulate the thyroid. In hyperthyroidism, there is an overproduction of thyroid hormones, commonly due to Graves’ disease, leading to suppression of TSH. These hormonal imbalances affect metabolism and multiple organ systems.

Signs and Symptoms

• Hypothyroidism
  1. Fatigue and lethargy
  2. Weight gain despite poor appetite
  3. Cold intolerance
  4. Dry skin and hair thinning
  5. Constipation
  6. Depression or slow thinking
  7. Menstrual irregularities
  8. Bradycardia and puffiness of the face
• Hyperthyroidism
  1. Weight loss despite increased appetite
  2. Palpitations and tachycardia
  3. Heat intolerance and sweating
  4. Tremors
  5. Anxiety and irritability
  6. Frequent bowel movements
  7. Irregular periods
  8. Eye signs (e.g., exophthalmos in Graves’ disease)

Risk Factors

• Female gender (more common in women)
• Age over 50 years
• Personal or family history of thyroid disease
• Autoimmune conditions like type 1 diabetes or coeliac disease
• EthnicHistory of neck irradiation or thyroid surgery
• Iodine imbalance
• Use of certain medications (e.g., amiodarone)

Investigations

1. Blood tests:

• TSH (first-line test)
• Free T4 and Free T3
• Thyroid peroxidase (TPO) antibodies in suspected autoimmune disease

2. Imaging:

• Ultrasound of the thyroid to detect nodules, goitre, or cysts
• Radioactive iodine uptake scan for functional assessment in hyperthyroidism

3. Fine-needle aspiration (FNA):

Performed if a suspicious thyroid nodule is found to rule out malignancy

Management

1. Non-Pharmacological Management

• Patient education and support
• Monitoring in subclinical or mild cases
• Smoking cessation (especially important in Graves’ orbitopathy)
• Dietary advice (adequate iodine, avoid goitrogens)

2. Pharmacological Management

• Hypothyroidism::
  1. Lifelong levothyroxine replacement therapy
  2. Dose adjusted based on TSH levels
• Hyperthyroidism::
  1. Antithyroid drugs like carbimazole or propylthiouracil
  2. Beta-blockers (e.g., propranolol) to control symptoms
  3. Radioiodine therapy to reduce thyroid activity

Regular blood tests are required to monitor thyroid hormone levels and adjust treatment.

3. Surgical Management

Indicated in cases of large goitre causing compressive symptoms, thyroid cancer, or when other treatments are ineffective. Thyroidectomy may be partial or total. Requires lifelong hormone replacement if total thyroidectomy is performed.

Complications

• Hypothyroidism:
  1. Myxoedema coma (rare but life-threatening)
  2. Hypercholesterolaemia
  3. Cardiovascular disease
  4. Infertility or menstrual disturbances
  5. Depression and cognitive impairment
• Hyperthyroidism:
  1. Atrial fibrillation
  2. Osteoporosis
  3. Thyroid storm (acute thyrotoxicosis, medical emergency)
  4. Eye complications in Graves’ disease
  5. Infertility and pregnancy complications

References

• NICE Clinical Knowledge Summaries (CKS): Hypothyroidism and Hyperthyroidism
• NICE Guideline NG145: Thyroid disease: assessment and management
• Royal College of Physicians: Endocrinology and thyroid disease guidelines
• British Thyroid Association: Management of thyroid nodules and cancer
• General Medical Council (GMC) Good Clinical Practice