A 7 year old female child presented with swelling over the body since 1 year, lethargy and loss of appetite since 6 months, cold intolerance since 5 months and constipation since 3-4 months. Her milestones were normal and scholastic performance was good. On examination she had a dull look with puffiness of eyes (myxedematous facies) and coarse and dry hair. No goiter was palpable. There was non-pitting edema over the limbs and skin was dry, coarse and hyperpigmented. There was delayed relaxation of deep tendon reflexes and heart sounds appeared muffled. A clinical diagnosis of hypothyroidism was considered (to rule out Addison’s disease in view of hyperpigmentation). (Fig 1)
Her thyroid function tests showed low T3 [24 ng/dl (Normal = 60-200 mcg/dl)], low T4 [0.5 mcg/dl (Normal = 4.4-12 mcg/dl] and high TSH [>100 mcIU/ml (Normal = 0.4-6 mcIU/ml] suggestive of primary hypothyroidism. Her bone age was around 4 years with height of 106 cms. In view of childhood onset hypothyroidism without goiter, autoimmune thyroiditis was considered. Her Antimicrosomal antibody (TPO) was 381 IU/ml [Normal = 0 to 35 IU/ml] and Thyroglobulin Antibody (ATA) was 301 IU/ml (Normal = 0 to 40 IU/ml) confirming Lymphocytic thyroiditis. Her ultrasound of the thyroid gland was normal. X-Ray skull showed no widening of the sella turcica. Her serum electrolytes and blood pressure were normal ruling out Addison’s disease. She was treated with L-Thyroxine (25 mcg daily), which she tolerated well. She was advised regular follow up and gradual increase in thyroxine dose till euthyroid state is achieved.
Acquired Hypothyroidism
The most common cause of acquired hypothyroidism in iodine – sufficient regions is autoimmune thyroiditis. In iodine deficient counties, iodine deficiency remains the most common thyroid disease.
Other causes of childhood onset of hypothyroidism are:
- Ectopic thyroid or dysgenesis – Late onset
- Drug induced hypothyroidism e.g. amiodarone
- Environmental goitrogens
- Central hypothyroidism (Hypothalamic or Pituitary)
- Radioiodine ablation or surgery.
Acquired hypothyroidism can occur at any age. These children present with growth failure, myxedematous change of skin, constipation, cold intolerance, decreased energy and an increased need for sleep. Scholastic performance is usually not affected. Bone age is delayed and is an indication of the duration of hypothyroidism. Adolescents have delayed puberty whereas younger children may have pseudoprecocious puberty. (Postulated to be due to high TSH concentrations binding to FSH receptor and subsequent stimulation).
Some children may present with headache and visual problems, which may be in long standing hypothyroidism due to hyperplastic enlargement of pituitary gland as a result of thyrotroph hyperplasia.
Treatment consists of thyroid hormone supplementation but in children with long standing hypothyroidism, catch up growth may be incomplete. The thyroxine initially should be replaced in low doses followed by gradual increase in the dose till euthyroid state is achieved and keeping the child on maintenance dose to decrease incidence of pseudotumor cerebri and cardiac failure. During the first year deterioration of school work, poor sleeping habits, restlessness and behavioral problems may occur but it is transient and partially ameliorated by starting at sub replacement supplementation and increasing slowly.
Autoimmune thyroiditis: Autoimmune thyroiditis is the most common cause of thyroid disease in children and adolescents leading to goiter or acquired hypothyroidism with/without a goiter.
A variety of different thyroid antigen antibodies are involved that block the thyrotropin receptors or inhibit enzyme activity leading to lymphocytic infiltration of the thyroid and hyperplasia. Later on follicles may atrophy. Certain haplotypes such as HLA-DR4, HLA-DR5 are associated with increased risk of goiter and thyroiditis and HLA-DR3 with atrophic variety of thyroiditis.
Thyroid antiperoxidase antibodies (TPO Abs/ antimicrosomal antibodies), antithyroglobulin antibodies and thyrotropin receptor blocking antibodies may be positive in autoimmune thyroiditis.
The disease in children is more common in females than in males with onset usually after 4 years of age with a peak during adolescence. Children with Down’s syndrome and girls with Turner’s syndrome are at risk.
Clinical Presentation – It may present as:
- Thyromegaly with euthyroidism (Asymptomatic goiter)
- Toxic thyroiditis
- Hypothyroidism with/without thyromegaly.
