Assessing Thyroid Function in Infants and Children

Iodine status of Queensland children and the associations with diet and thyroid function

“…The general interpretation of thyroid function test, TSH, fT4 and fT3 are outlined in table 2.4. Where hypothyroidism is prevalent, TSH levels are elevated above normal range and fT4 levels fall below normal range (71). Hyperthyroidism, on the other hand, is determined by a decrease in TSH and an increase in fT4 in addition to elevated fT3 (71).…”

“…Where hypothyroidism is prevalent, TSH levels are elevated above normal range and fT4 levels fall below normal range (71). Hyperthyroidism, on the other hand, is determined by a decrease in TSH and an increase in fT4 in addition to elevated fT3 (71). Although in adults, TSH is used as maker for detecting hyper-or hypothyroidism, in children TSH alone is known to have inconsistent normal ranges depending on age (71).…”

“…Hyperthyroidism, on the other hand, is determined by a decrease in TSH and an increase in fT4 in addition to elevated fT3 (71). Although in adults, TSH is used as maker for detecting hyper-or hypothyroidism, in children TSH alone is known to have inconsistent normal ranges depending on age (71). Despite these inconsistencies, abnormal TSH often precedes other abnormal hormone levels and it is for this reason that measuring both TSH and fT4 is the most preferable method when evaluating thyroid dysfunction in children (71).…”

“…Although in adults, TSH is used as maker for detecting hyper-or hypothyroidism, in children TSH alone is known to have inconsistent normal ranges depending on age (71). Despite these inconsistencies, abnormal TSH often precedes other abnormal hormone levels and it is for this reason that measuring both TSH and fT4 is the most preferable method when evaluating thyroid dysfunction in children (71). The combined analysis of TSH, fT4 and fT3 will provide substantial diagnostic information for both hypothyroidism and hyperthyroidism to be detected if present (70,71).…”

“…The relationship between iodine intake and Tg levels are outlined in table 2.5. Closely associated with UIC, Tg is becoming a popular indicator to use in increasing dietary iodine environments (68,71). The WHO reference range for Tg in iodine sufficient children aged 5-14 years is 4-40 ug/L (1).…”