Growth defect and Thyroid Hormone Resistance

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One hallmark of hypothyroidism is a growth defect with bone age

delay. We found that persons with resistance to thyroid hormone are

shorter than persons without resistance; 18% had short stature and

no catch-up growth later in life. However, bone age is delayed in

only a minority of children with resistance to thyroid hormone.

The abnormal growth in persons with resistance could involve both

direct and indirect (through growth hormone or insulin-like growth

factor secretion or action) effects of thyroid hormone on bone.

Moreover, the lower IQ in persons of short stature with resistance

to thyroid hormone suggests relative hypothyroidism in brain and

bone. Children (but not adults) with resistance are less likely to

have short stature when their mothers have resistance (9% when the

mother has resistance compared with 23% when the mother is

unaffected)