Hypothyroidism

Hypothyroidism is a common endocrine disorder where the thyroid gland does not produce sufficient thyroid hormone. It can have various causes, affect multiple body systems, and its management is a key aspect of general practice. Here’s an overview:

Causes of Hypothyroidism

Primary Hypothyroidism:

  • Hashimoto’s thyroiditis: An autoimmune condition, the most common cause.
  • Iatrogenic: Post-radioactive iodine treatment or thyroidectomy.
  • Iodine deficiency: Rare in developed countries due to iodized salt.
  • Congenital hypothyroidism: Thyroid dysgenesis or dyshormonogenesis.
  • Medications: Such as lithium, amiodarone, interferon-alpha.

Secondary Hypothyroidism:

  • Pituitary gland dysfunction: Leading to low TSH production.
  • Hypothalamic disease: Affecting TRH release.

Transient:

  • Subacute thyroiditis
  • Postpartum thyroiditis

Diagnosis of Hypothyroidism

  • Clinical Presentation:
    • Symptoms include fatigue, weight gain, cold intolerance, constipation, dry skin, hair loss, bradycardia, and menstrual irregularities.
    • Signs may include goiter, bradycardia, delayed relaxation phase of deep tendon reflexes, and myxedema (in severe cases).
  • Laboratory Tests:
    • TSH Test: Elevated TSH is the primary test for hypothyroidism.
    • Free T4: Low levels confirm the diagnosis.
    • Antibodies: Anti-thyroid peroxidase (anti-TPO) antibodies are usually present in Hashimoto’s thyroiditis. Anti-thyroglobulin antibodies may also be present but are less specific
  • Additional Tests:
    • Lipid profile, FBC, and liver function tests may show secondary effects of hypothyroidism ie increased LDL, anaemia, elevated AST and ALT.

Differential Diagnosis

  • Other causes of fatigue and weight gain such as depression, adrenal insufficiency, sleep apnea.
  • Secondary causes of hypothyroid symptoms like pituitary or hypothalamic disorders.
  • Non-thyroidal illness syndrome or “euthyroid sick syndrome” where thyroid function tests are altered by another illness.

Management of Hypothyroidism

  • Levothyroxine Therapy:
    • Standard treatment involves replacement with levothyroxine.
    • Dosage is individualized based on weight, age, and severity.
    • Monitoring: TSH levels are monitored to adjust the dose (6 weeks are required to see the full impact of any change)
  • Lifestyle and Diet:
    • General health advice regarding diet and exercise.
    • Selenium and iodine supplementation might be considered in specific cases.
  • Special Considerations:
    • Pregnancy: Requires careful monitoring and adjustment of levothyroxine dose. Many women require a dose increase of 25-50%
    • Elderly patients may require lower initial doses.
    • Heart disease: Caution with starting doses due to potential for exacerbating cardiac conditions.
  • Regular Monitoring:
    • Periodic TSH and free T4 levels to ensure adequate treatment.
    • Monitoring for symptoms of over-replacement like palpitations, anxiety, or insomnia and under-replacement such as fatigue
  • Referral to Endocrinology:
    • In cases of difficulty in maintaining euthyroid state, pregnancy, or heart disease.
    • When secondary hypothyroidism is suspected.

Conclusion

Hypothyroidism management is typically straightforward, involving hormone replacement and regular monitoring. However, attention must be paid to each patient’s unique context, including age, comorbidities, and specific causes of the condition, to optimize treatment and outcomes.

Overview of Thyroid Disorders

Thyroid disorders are common endocrine conditions with varying presentations, ranging from asymptomatic biochemical abnormalities to life-threatening thyrotoxicosis or myxedema coma.

Diagnosis of Thyroid Disorders:

  • Hypothyroidism:
    • Clinical Presentation: Symptoms may include fatigue, weight gain, cold intolerance, constipation, dry skin, and hair loss.
    • Laboratory Tests: Diagnosis is primarily based on elevated serum Thyroid Stimulating Hormone (TSH) levels with low free Thyroxine (T4).
    • Antibody Testing: Anti-thyroid peroxidase (anti-TPO) antibodies may be checked to assess for autoimmune thyroiditis (Hashimoto’s Thyroiditis).
  • Hyperthyroidism:
    • Clinical Presentation: Symptoms can include weight loss, heat intolerance, tremor, palpitations, and anxiety.
    • Blood Tests:
      • Low TSH and High Free T4 and/or T3: Indicative of hyperthyroidism.
      • Thyroid Receptor Antibody (TRAb): Positive in Graves’ disease.
    • Radioactive Iodine Uptake (RAIU) Test: Differentiates between Graves’ disease (diffuse high uptake), toxic multinodular goiter (patchy uptake), and thyroiditis (low uptake)..
  • Thyroid Nodules and Cancer:
    • Physical Examination: A lump or swelling in the neck could indicate a thyroid nodule.
    • Ultrasound: Used to characterize nodules and guide fine-needle aspiration biopsy.
    • Fine-needle Aspiration Biopsy: Determines the nature of the nodule (benign vs. malignant).
  • Subclinical Thyroid Disorders:
    • Subclinical Hypothyroidism: Elevated TSH with normal free T3 and T4.
    • Subclinical Hyperthyroidism: Suppressed TSH with normal free T3 and T4.

Management of Thyroid Disorders:

  • Hypothyroidism:
    • Levothyroxine Replacement: The mainstay of treatment, dosing is individualized based on TSH levels and patient symptoms.
    • Monitoring: Regular TSH and free T4 checks to adjust levothyroxine dosage.
    • Special Considerations: Attention to elderly patients, pregnant women, and those with cardiac disease is important for dose adjustments.
  • Hyperthyroidism:
    • Antithyroid Medications: Thionamides such as carbimazole or propylthiouracil are used to control hyperthyroidism, especially in Graves’ disease.
    • Beta-Blockers: Used for symptom control.
    • Radioiodine Therapy: A common definitive treatment for Graves’ disease and toxic nodular goiter.
    • Surgery: Thyroidectomy may be indicated in large goiters, suspicion of cancer, or when other treatments are contraindicated or unsuccessful.
    • Monitoring: Regularly monitoring thyroid function tests is crucial to avoid overtreatment or undertreatment.
  • Thyroid Nodules and Cancer:
    • Surgery: Thyroidectomy is the primary treatment for malignant nodules.
    • Radioactive Iodine: Used postoperatively in certain types of thyroid cancer.
    • TSH Suppression Therapy: Levothyroxine is used to suppress TSH in thyroid cancer patients to reduce the risk of recurrence.
    • Surveillance: Ultrasound and serum thyroglobulin are used for surveillance after treatment for thyroid cancer.
  • Subclinical Disorders:
    • Subclinical Hypothyroidism: Monitor for progression to overt hypothyroidism; consider treatment if TSH is significantly elevated or if symptoms arise.
    • Subclinical Hyperthyroidism: Monitor for progression to overt hyperthyroidism and assess for osteoporosis and atrial fibrillation if TSH remains suppressed.

General Considerations:

  • Pregnancy: Thyroid hormone is crucial for fetal development, so management must be closely coordinated in pregnant patients.
  • Iodine Intake: Adequate dietary iodine is important for thyroid function.
  • Long-term Follow-up: Many thyroid disorders require lifelong monitoring and treatment.
  • Patient education: on the chronic nature of most thyroid disorders, the importance of adherence to prescribed treatments, and regular follow-up for medication titration and monitoring of potential complications is an integral part of management.