Serum vitamin A concentration is elevated in idiopathic intracranial hypertension

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Abstract
Objective: The primary purpose was to investigate whether serum vitamin A concentration is associated with idiopathic intracranial hypertension (IIH). The secondary aim was to obtain pilot data regarding the amount of vitamin A ingested by patients and controls. Background: Vitamin A is an attractive candidate mediator of IIH as many of the symptoms and signs of hypervitaminosis A mimic those of IIH. Methods: We prospectively determined serum retinol and retinyl ester concentration in 16 women with IIH and 70 healthy young women. Using a survey instrument, we also determined the average daily vitamin A ingestion in a convenience sample of patients and controls. Results: Serum retinol concentration was significantly higher in the patient group (median 752 ug/L) compared with the control group (median 530 ug/L), even after adjusting for age and body mass index (p < 0.001). Retinyl ester concentration, however, was similar in the patient (median 48 ug/L) and control (median 41 ug/L) groups (p = 0.32). There was no significant correlation between serum retinol concentration and body mass index in the patients (r = 0.16) or controls (r = −0.02). Finally, there was no significant difference in the amounts of vitamin A ingested by the patients or controls, although the small number of subjects in both groups reduced the power of this conclusion. Conclusions: Elevated serum retinol concentration is associated with IIH. Obesity, by itself, does not explain these higher levels. Patients may ingest an abnormally large amount of vitamin A, metabolize it abnormally, or be unusually sensitive to its effects. Alternatively, elevated level of serum retinol may reflect an epiphenomenon of another variable we did not measure or a nonspecific effect of elevated retinol binding capacity.