In England and Wales, the National Institute for Health and Care Excellence (NICE) recommends routine T4 testing in children, and T3 testing in both adults and children if central hypothyroidism is suspected and the TSH is low. There are a number of symptom rating scales for hypothyroidism; they provide a degree of objectivity but have limited use for diagnosis. Many cases of hypothyroidism are associated with mild elevations in creatine kinase and liver enzymes in the blood. They typically return to normal when hypothyroidism has been fully treated. Levels of cholesterol, low-density lipoprotein and lipoprotein (a) can be elevated; the impact of subclinical hypothyroidism on lipid parameters is less well-defined.Very severe hypothyroidism and myxedema coma are characteristically associated with low sodium levels in the blood together with elevations in antidiuretic hormone, as well as acute worsening of kidney function due to a number of causes. In most causes, however, it is unclear if the relationship is causal.A diagnosis of hypothyroidism without any lumps or masses felt within the thyroid gland does not require thyroid imaging; however, if the thyroid feels abnormal, diagnostic imaging is then recommended. The presence of antibodies against thyroid peroxidase (TPO) makes it more likely that thyroid nodules are caused by autoimmune thyroiditis, but if there is any doubt, a needle biopsy may be required. Central
If the TSH level is normal or low and serum free T4 levels are low, this is suggestive of central hypothyroidism (not enough TSH or TRH secretion by the pituitary gland or hypothalamus).
Hypothyroidism in early pregnancy, even with limited or no symptoms, may increase the risk of pre-eclampsia, offspring with lower intelligence, and the risk of infant death around the time of birth. Women are affected by hypothyroidism in 0.3–0.5% of pregnancies. Subclinical hypothyroidism during pregnancy is associated with gestational diabetes, low birth-weight, placental abruption, and the birth of the baby before 37 weeks of pregnancy. Children
Newborn children with hypothyroidism may have normal birth weight and height (although the head may be larger than expected and the posterior fontanelle may be open). Some may have drowsiness, decreased muscle tone, a hoarse-sounding cry, feeding difficulties, constipation, an enlarged tongue, umbilical hernia, dry skin, a decreased body temperature, and jaundice. A goiter is rare, although it may develop later in children who have a thyroid gland that does not produce functioning thyroid hormone. A goiter may also develop in children growing up in areas with iodine deficiency. Normal growth and development may be delayed, and not treating infants may lead to an intellectual impairment (IQ 6–15 points lower in severe cases). Other problems include the following: difficulty with large scale and fine motor skills and coordination, reduced muscle tone, squinting, decreased attention span, and delayed speaking. Tooth eruption may be delayed.In older children and adolescents, the symptoms of hypothyroidism may include fatigue, cold intolerance, sleepiness, muscle weakness, constipation, a delay in growth, overweight for height, pallor, coarse and thick skin, increased body hair, irregular menstrual cycles in girls, and delayed puberty.