This is one of the most common endocrine conditions seen in childhood. It is basically related to low levels of thyroid hormone in the blood due to many reasons as will be discussed here. There are two types of hypothyroidism in children - congenital and acquired.

What are the causes??

-> primary hypothyroidism

- congenital

  1. dysgenesis- aplasia, hypoplasia or ectopic thyroid
  2. inborn errors of thyroid hormone synthesis
  3. insensitivity or resistance to thyroid hormone- inherited defects
  4. maternal medication- radioiodine, carbimazole

- acquired

  1. iodine deficiency
  2. auto-immune chronic lymphocytic thyroiditis - hashimoto’s
  3. irradiation - therapeutic radio-iodine, after treatment of lymphoma’s
  4. surgical ablation
  5. ingestion of goitrogens
  6. drug induced- iodides, carbimazole, lithium

-> secondary hypothyroidism

  1. due to deficiency of Thyroid stimulating hormone [TSH] or thyrotropin releasing hormone [TRH]
  2. hypopituitarism

What are the features of this conditions? How does it present?

-> Congenital

  • One of the earliest signs- a patent posterior fontanel and wide open cranial sutures. This is due to  in utero lag in skeletal maturation.
  • The skin is dry, thick, coarse, cool and mottled.
  • Abdomen is large.
  • Birth weight maybe higher than the average but they are lethargic and less active.
  • They sleep most of the day, cry little, feed poorly and often have choking spells during feeding.
  • Respiratory difficulties like noisy breathing, nasal obstruction and apnea are seen.
  • Due to delayed maturation of glucoronide conjugation physiological jaundice persists for a longer time.
  • These babies are constipated and hypothermia is quite common too.
  • By  8-10 weeks the characteristic facial features develop- puffy face, swollen eyelids, narrow palpebral fissures, widely separated eyes, broad nose with depressed bridge, open mouth with broad thick protuberant tongue.
  • The neck is short and thick and supraclavicular pad of fat may be present. The voice is hoarse.
  • The skin  appears pale yellow due to carotenemia and is also dry, scaly and thick. Hair is sparse coarse and brittle, it grows down on the forehead.
  • The muscles are flaccid and hpyotonic. In rare cases like with Kocher- Debre-Semelaigne Syndrome.
  • There is marked physical and mental retardation- social smile is delayed and attention span is poor.
  • Occasionally sexual precocity may be present.
  • Deep tendon reflexes are delayed.
  • Cardiomegaly, heart murmurs, slow pulse and refractory anemia are common.

-> Acquired

  • growth retardation
  • delayed skeletal maturation
  • delayed dental development
  • delayed puberty
  • myopathy
  • enlarged sella tursica
  • pseudomotor cerebri

How do you diagnose this condition??

  1. Serum levels of T4 and T3[free or total] are low or  borderline.
  2. If the defect is primarily in the thyroid - the TSH level will be high often above 100µg/ml.
  3. Serum prolactin levels are elevated.
  4. Serum antibodies indicate hashimoto’s.
  5. Radioactive iodine uptake studies also help with the diagnosis.
  6. Thyroid ultrasound is not as beneficial as radionuclide scanning.
  7. Iodine deficiency is found by urine examination- low iodine excretion
  8. FNAC is helpful if the thyroid grows in size despite the treatment.
  9. TRH assay is done to detect hypothyroidism secondary to hypothalamic or pituitary damage.
  10. X-Rays of bone show the effect of the condition on the skeletal framework and its growth and development.
  11. ECG changes are seen
  12. Serum cholesterol is usually elevated.

What is the prognosis??

This depends on the degree of thyroid hypo-function, the age of the patient, initiation of treatment and compliance of the patient and adequacy of management.