Sir.—Cassidy et al1 described a 7-year-old girl with Russell-Silver syndrome and deficiencies of growth hormone, corticotropin, and thyroid-stimulating hormone.
nosis of corticotropin deficiency was based on an inadequate 11-desoxycortisol response (3.3 μg/dL
[0.096 μmol/L]) to metyrapone. However, a simultaneous serum cortisol level was not reported and such a determination is necessary to properly interpret a low 11-desoxycortisol response.2 The serum cortisol level should be less than 5 μg/dL (140 nmol/L) to ensure that the metyrapone was indeed taken, absorbed, and able to suppress cortisol production by inhibiting 11B-hydroxylase. The normal increments of cortisol following a fast suggest normal hypothalamic-corticotropin-adrenal function in this patient.
Cassidy et al also reported that the patient required twice the recommended dose of human growth hormone to achieve normal growth for age and they suggested that perhaps other patients with Russell-Silver syndrome and growth hormone deficiency might require increased amounts of growth hormone