Acquired Hypothyroidism in Children
Acquired hypothyroidism is a condition where the thyroid gland fails to produce enough thyroid hormones after infancy. The clinical presentation is often subtle and gradual, leading to a delay in diagnosis. Early identification and treatment are crucial to prevent long-term complications, particularly with growth and development.
Aetiology
Primary Hypothyroidism: This is the most common form, where the problem lies within the thyroid gland itself.
Autoimmune Thyroiditis (Hashimoto’s Thyroiditis): This is the leading cause in the UK and other developed countries. It involves a chronic lymphocytic infiltration of the thyroid gland, leading to its destruction.
Iodine Deficiency: While the most common cause globally, it is rare in the UK due to a sufficient dietary intake of iodine.
Iatrogenic: This can be caused by surgery, radiotherapy to the neck, or certain drugs like amiodarone.
Central Hypothyroidism: This is a rarer form where the issue lies in the pituitary gland or hypothalamus, resulting in insufficient TSH stimulation of the thyroid gland. Causes include CNS tumours, cranial radiotherapy, or pituitary abnormalities.
Clinical Presentation
Symptoms are often non-specific and may be mistaken for other conditions.
Growth and Development: A key sign is a reduced height velocity and delayed bone age. Younger children may also show signs of delayed puberty or, paradoxically, pseudo-precocious puberty.
Metabolic: Children may experience weight gain and cold intolerance. In more severe cases, this can lead to Slipped Upper Femoral Epiphysis (SUFE).
General Symptoms: Common complaints include tiredness, lethargy, constipation, and dry, thick skin.
Goitre: An enlarged thyroid gland (goitre) can be a presenting feature in primary hypothyroidism, as the gland attempts to compensate for the low hormone levels.
Investigations
Primary Hypothyroidism: The diagnosis is confirmed with a high TSH and a low free .
Central Hypothyroidism: Diagnosis is confirmed by a low free and a low or inappropriately normal TSH.
Thyroid Antibodies: The presence of anti-thyroid peroxidase (TPO) and anti-thyroglobulin (Tg) antibodies supports a diagnosis of Hashimoto’s thyroiditis.
Management
Hormone Replacement: The cornerstone of management is adequate replacement with a synthetic thyroid hormone, levothyroxine (25–200 micrograms once daily).
Monitoring: Thyroid function tests (TSH and ) are monitored every 4–6 months initially, and then annually once the dose is stable.
Goals: The goal of treatment is to normalise the TSH and levels, resolve symptoms, and ensure a return to normal growth velocity.