Hypothyroidism in cystinosis.

It has recently been shown that hypothyroidism complicates cystinosis. The radiographic bone changes of hypothyroidism (retarded skeletal age) cannot be detected while the patient has overt rickets, since the secondary ossification centers are not ossified. When the rickets is treated and the secondary ossification centers fail to appear (the skeletal age remains retarded), then the diagnosis of hypothyroidism should be suspected. After treatment with thyroid hormone is begun and a growth spurt occurs, rickets that has been controlled may reactivate. The previous doses of vitamin D will no longer be adequate because of the patient's growth spurt.