[More recent aspects of treatment for hypothyroidism and goitre in children and adolescents (author's transl)].

According to more recent knowledge L-thyroxine alone is recommended for thyroid hormone replacement therapy, no longer the combination of L-thyroxine and triiodothyronin, since L-thyroxine is converted to triiodothyronine in the periphery of the body. Additional application of triiodothyronine causes unphysiological elevations of blood levels of triiodothyronine. When changing from the combined thyroid hormone therapy to treatment with L-thyroxine alone it is enough in most cases to replace the previous amount of L-thyroxine only; previous recommendations for the dosage of thyroid hormone were rather high. Average requirements of adults for L-thyroxine are around 170 mug per day. Children need about 90--100 mug per m2 body surface per day. -- When hypothyroidism is suspected in newborns or infants no protracted diagnostic procedures are justified with respect to brain development and its requirement of thyroid hormone during this period of life. Replacement therapy should be started within 1--2 days. The exact diagnosis can be established later, for instance during the third day of life when a temporary interuption of treatment for diagnostic purposes has no longer such negative effect on normal brain development. As long as physiological doses of L-thyroxine are used no side effects are to be expected for patients who later turn out to be euthyroid. -- Following exclusion of hyperthyroidism goitres in children and adolescents equally need thyroid hormone replacement therapy to reduce the size or prevent further enlargement or even the development of nodules within the gland. The dosage for this is about half to three quarters of the full replacement dose. The nature of thyroid nodules should be investigated, even surgically, since malignancies can develop in children and juveniles as well as in adults.