Relative or absolute lack of thyroid hormones or resistance to thyroid hormone 

Endemic (iodine deficiency), autoimmune (Hashimoto’s thyroiditis), congenital, drugs (e.g. lithium, amiodarone), thyroiditis (atrophic, post-partum), following thyroidectomy or radioiodine treatment, hypopituitarism

Dry skin, hoarse voice, hair loss, hypothermia, bradycardia, macroglossia, slowed reflexes, heart failure, serous effusions (e.g. pleural, pericardial)

Lethargy, weight gain, cramps, constipation, cold intolerance, peri-orbital oedema, menorrhagia, ataxia, confusion (elderly), psychosis, depression

Bloods: TFTs: Decreased T4, decreased T3, increased TSH, thyroid antibodies – 

 Autoantibodies against thyroid peroxidase thyroglobulin in Hashimoto’s 

Thyroiditis

Ultrasound Scan: Thyroid

Replace with daily Levothyroxine for life and regular monitoring of thyroid function.