Makindo Medical Notes

Related Subjects: |Thyrotoxicosis and Hyperthyroidism |Thyroid Storm - Thyrotoxic crisis |Graves' Disease (Thyrotoxicosis) |Amiodarone and Thyroid disease |Thyroid Surgery (Thyroidectomy) |Hypothyroidism |Hashimoto's thyroiditis |DeQuervain's thyroiditis |Subacute Thyroiditis |Thyroid nodule |Congenital Hypothyroidism |Thyroid Function Tests and antibodies |Post partum thyroiditis |Sick Euthyroid Syndrome |Thyroid Exam (OSCE) |Thyroid Gland anatomy and Physiology |Thyroid Cancer

Hashimoto thyroiditis is an autoimmune inflammation of the thyroid that may be associated with other autoimmune conditions. It is characterized by high titres of thyroid peroxidase (TPO) antibodies.

About

• Hashimoto's thyroiditis is a common autoimmune disease causing chronic lymphocytic thyroiditis.
• It is associated with high titres of antibodies to thyroid peroxidase (TPO), seen in 90-100% of cases.
• The thyroid gland can become firm, hard, or rubbery in texture.

Aetiology

• High levels of thyroid peroxidase antibodies (TPO).

Associated with Other Autoimmune Conditions

• Pernicious anaemia, vitiligo, Addison's disease.
• Type 1 diabetes mellitus (DM), hypoparathyroidism, premature greying of hair.
• Coeliac disease, rheumatoid arthritis (RA), systemic lupus erythematosus (SLE).

Clinical Features

• Signs of hypothyroidism: tiredness, lethargy, weight gain.
• Depression, constipation, cold intolerance.
• Impaired memory, slowness of thought, dry and cold skin.
• Menstrual disturbances: heavy or infrequent periods.
• Bradycardia, hypothermia, heart failure, pericardial effusion.
• Musculoskeletal: myotonia, proximal myopathy, slow-relaxing ("hung-up") reflexes.
• Hashitoxicosis: Early phase with increased T4/T3 levels, causing transient hyperthyroidism.

Investigations

• Anaemia, usually macrocytic.
• Hyponatraemia, raised AST, and CK (suggesting myopathy).
• Raised cholesterol levels.
• Thyroid function tests: Elevated TSH with low free T4.
• Autoimmune markers: High titres of TPO antibodies (90-100%).
• TSH-binding inhibitory immunoglobulin (TBII).

Differential Diagnosis

• Primary hypothyroidism.
• Postpartum thyroiditis: Typically transient, occurring after pregnancy.
• Iodine deficiency: Leads to endemic goitre due to impaired T3/T4 production and elevated TSH levels.
• Pendred syndrome: A genetic condition involving a defect in thyroid hormone biosynthesis, often associated with hearing loss.

Management

• Commence levothyroxine (T4) therapy, typically 50-100 mcg/day, lifelong treatment.
• For elderly patients or those with ischaemic heart disease (IHD), start with a lower dose (e.g., 25 mcg daily) and increase gradually.
• Aim for normalization of TSH levels with treatment.

Prognosis

• In children, untreated hypothyroidism can lead to impaired brain development and cretinism.
• In the elderly, symptoms may be vague, leading to delayed diagnosis.