To determine the presence of structural abnormalities of the adrenal in late-onset adrenal hyperplasia, four consecutive patients were studied by MRI before beginning glucocorticoid replacement therapy. Three women were diagnosed as 21-hydroxylase deficient late-onset adrenal hyperplasia by a 17-OHP level > 1,000 ng/dL 30 minutes after acute adrenal stimulation, and one patient was diagnosed as 11-hydroxylase deficient late-onset adrenal hyperplasia when her 11-deoxycortisol level was threefold the upper 95th percentile of normal. Two patients with 21-hydroxylase deficient late-onset adrenal hyperplasia had normal adrenal glands on MRI. Another 21-hydroxylase deficient late-onset adrenal hyperplasia patient was noted to have a 2.5 x 3.3-cm left adrenal nodule, which had been documented some 4 years earlier on CT scan and had not changed in size during that interval. This patient was 40 years of age when the diagnosis of late-onset adrenal hyperplasia was established. The patient with 11-hydroxylase deficient late-onset adrenal hyperplasia demonstrated a diffuse enlargement of the left adrenal gland consistent with hyperplasia, with no focal lesions. In conclusion, although patients with late-onset adrenal hyperplasia may often demonstrate nodular or diffuse adrenocortical hyperplasia on MRI, not all patients with endocrinologically evident disease demonstrate such abnormalities, consistent with a lesser degree of ACTH stimulation compared with women with classical congenital adrenal hyperplasia.
