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Deficiency of thyroid hormone causing slowed metabolism and multisystem effects
Deficiency of thyroid hormone causing slowed metabolism and multisystem effects
Risk Factors
Family history of thyroid disease
Autoimmune conditions such as type 1 diabetes or coeliac disease
Female sex
History of thyroid surgery or irradiation
Iodine deficiency or excess
Aetiology
Congenital hypothyroidism due to thyroid agenesis dysgenesis or dyshormonogenesis
Acquired autoimmune hypothyroidism such as Hashimoto’s thyroiditis
Post-thyroidectomy or radioactive iodine therapy
Secondary hypothyroidism due to pituitary or hypothalamic disease
Drugs such as lithium or amiodarone
Pathophysiology
Insufficient thyroid hormone results in reduced basal metabolic rate
Increased TSH secretion in primary hypothyroidism due to negative feedback
Affects growth development and organ function especially in infancy and childhood
Diagnosis
Lethargy cold intolerance dry skin constipation weight gain poor growth
Delayed puberty bradycardia and goitre may be present
Congenital form may present with prolonged jaundice hypotonia poor feeding
Screening in newborns with TSH and T4
Elevated TSH and low free T4 in primary hypothyroidism
Anti-thyroid peroxidase or anti-thyroglobulin antibodies if autoimmune
Differential Diagnosis
Central hypothyroidism due to pituitary disease
Down syndrome
Other causes of failure to thrive or delayed development
Chronic illness or malnutrition
Investigations
Serum TSH and free T4 levels
Thyroid antibodies for autoimmune thyroiditis
Newborn screening TSH
Thyroid ultrasound or scan in unclear cases
Pituitary imaging if central hypothyroidism suspected
Management
Levothyroxine orally once daily
Dose adjusted by weight and TSH monitoring
Monitoring every 4–6 weeks in infancy then 3–6 monthly
Education on adherence and avoiding co-administration with calcium or iron
Complications & Prognosis
Poor linear growth or developmental delay if untreated
Delayed puberty or menorrhagia
Goitre
Good prognosis with early diagnosis and appropriate treatment
Congenital form requires prompt therapy to prevent intellectual disability
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