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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 ischemic 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.