Hypothyroidism refers to insufficient thyroid hormones, triiodothyronine (T3) and thyroxine (T4). Thyroid hormone is essential for the development and functioning of the brain and body. Undiagnosed hypothyroidism can lead to significant problems with neurodevelopment and intellectual disability.
In children, hypothyroidism may be congenital or acquired.
Congenital Hypothyroidism
Congenital hypothyroidism refers to when hypothyroidism develops before birth. This occurs in around 1 in 3000 newborns. It can be the result of:
- Thyroid dysgenesis (an underdeveloped thyroid gland)
- Dyshormonogenesis (a fully developed gland that does not produce enough hormone)
- Pituitary or hypothalamus pathology (rare)
Congenital hypothyroidism is screened for on the newborn blood spot screening test.
Where it is not picked up a birth, patients can present with:
- Prolonged neonatal jaundice
- Poor feeding
- Constipation
- Reduced activity
- Slow growth
- Delayed development
Acquired Hypothyroidism
Acquired hypothyroidism refers to when hypothyroidism develops after previously normal thyroid function.
Hashimoto’s thyroiditis, an autoimmune condition causing inflammation and damage to the thyroid gland, is the most common cause. Hashimoto’s thyroiditis is associated with:
- Anti-thyroid peroxidase (anti-TPO) antibodies
- Anti-thyroglobulin (anti-Tg) antibodies
- Other autoimmune conditions, particularly type 1 diabetes and coeliac disease
Blood tests will show:
- Low T3 and T4
- Raised TSH (due to a lack of negative feedback on the pituitary gland)
This can lead to symptoms of:
- Fatigue and low energy
- Poor growth
- Weight gain
- Poor school performance
- Constipation
- Dry skin and hair loss
Management
Investigations include thyroid function blood tests (TSH, T3 and T4), thyroid ultrasound and thyroid antibodies.
Levothyroxine, taken orally once a day, replaces the normal thyroid hormones. Doses are titrated based on thyroid function tests and symptoms.
Last updated March 2025
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