Thyroid Disorders: Functions Diagnosis and Treatment

Explain the physiological role of thyroid hormones., What are the differences between hypothyroidism and hyperthyroidism and how are these conditions diagnosed and treated?

Thyroid Hormones: Functions, Disorders, and Treatment

Physiological Role of Thyroid Hormones

• Thyroid gland secretes triiodothyronine (T3) and thyroxine (T4), regulated by thyroid-stimulating hormone (TSH) from the pituitary gland.
• Functions:
  • Regulate metabolism, energy production, and temperature control.
  • Influence cardiovascular, neurological, and digestive functions.
  • Essential for fetal brain development and growth.
• HPT Axis Control:
  • Hypothalamus releases thyrotropin-releasing hormone (TRH).
  • Pituitary releases TSH in response to TRH.
  • Thyroid produces T3 and T4, which exert negative feedback on TRH and TSH.

Hypothyroidism

• Cause: Autoimmune (Hashimoto’s thyroiditis), iodine deficiency, congenital defects, radiation therapy, medications (lithium, amiodarone).
• Symptoms:
  • Fatigue, weight gain, cold intolerance.
  • Depression, dry skin, brittle hair, constipation.
  • Slow heart rate (bradycardia), muscle weakness.
• Complications:
  • Myxedema coma (severe untreated hypothyroidism).
  • Cardiovascular disease (increased cholesterol levels).
• Diagnosis:
  • High TSH, low T3/T4 in primary hypothyroidism.
  • Thyroid antibodies (anti-TPO, anti-thyroglobulin) in Hashimoto’s.
• Treatment:
  • Levothyroxine (T4 replacement): Taken daily, dose adjusted based on TSH.
  • Regular monitoring to avoid over- or under-treatment.

Hyperthyroidism

• Cause:
  • Autoimmune (Graves’ disease – most common).
  • Toxic multinodular goiter, subacute thyroiditis, iodine excess.
• Symptoms:
  • Weight loss, heat intolerance, excessive sweating.
  • Anxiety, tremors, rapid heartbeat (tachycardia).
  • Bulging eyes (exophthalmos) in Graves’ disease.
• Complications:
  • Thyroid storm (life-threatening hyperthyroid crisis).
  • Atrial fibrillation, osteoporosis, muscle wasting.
• Diagnosis:
  • Low TSH, high T3/T4.
  • Thyroid-stimulating immunoglobulin (TSI) for Graves’ disease.
  • Radioactive iodine uptake (RAIU) scan to differentiate causes.
• Treatment:
  • Antithyroid drugs (ATDs): Methimazole (first-line), Propylthiouracil (PTU in pregnancy).
  • Radioactive iodine (RAI) therapy: Destroys thyroid tissue over time.
  • Surgery (thyroidectomy): Reserved for severe cases or large goiter.
  • Beta-blockers (propranolol, atenolol) for symptom control.

Thyroid Disorder Diagnosis

• Blood tests: TSH, free T3, free T4 levels.
• Imaging: Thyroid ultrasound for nodules, RAI uptake for hyperthyroidism.
• Biopsy: Fine-needle aspiration (FNA) for suspicious nodules.

Long-Term Management Considerations

• Regular monitoring: Adjust levothyroxine or ATD doses based on lab results.
• Nutritional factors:
  • Iodine-rich diet (for deficiency prevention).
  • Avoid excess iodine in hyperthyroidism.
• Lifestyle modifications:
  • Manage stress, maintain a balanced diet, exercise.
  • Monitor bone health in hyperthyroid patients (risk of osteoporosis). APA