IMPAIRED CORTISOL SECRETION IN ABETALIPOPROTEINEMIA

Abstract

In the adrenal gland cholesterol for steroid biosynthesis is derived from both de novo biosynthesis and receptor mediated uptake of plasma lowdensity lipoproteins (LDL). In the present study we have compared ACTH stimulated adrenal production of cortisol in four control subjects and one adult male patient with abetalipoproteinemia, a disorder in which LDLis absent. Basal morning cortisol levels in theplasma in thecontrol subjects (13.3 ± 1.6 μg/dl) andabetalipoproteinemic patient (14.6 μg/dl) were similar. During infusion of µl, 24 ACTH however, plasma cortisol levels were higher in the control subjects than in the abetalipoproteinemic patient and this difference was significant at times after 4 hours. Urinary excretionof both 17-hydroxy and 17-ketosteroids over the24 hour infusion period was also significantly lower in the abetalipoproteinemic patient indicating that cortisol production rates were reduced. Ourresults suggest that in theabsence of plasma lowdensity lipoproteins, as occurs in abetalipoproteinemia, themaximal production of adrenal corticosteroids is impaired. By inference, these findingslend in vivo support to the view that plasma low density lipoproteins serve as an important source of cholesterol foradrenal steroidogenesis in man.