Prevalence of diabetes and impaired glucose tolerance in adult hypopituitarism on low dose oral hydrocortisone replacement therapy

OBJECTIVE The conventional dosage of hydrocortisone, used for many years in the management of hypopituitarism (30 mg per day), has now been shown to b e more than is physiologically necessary. On this conventional corticostero id therapy studies have demonstrated an increased prevalence of diabetes an d impaired glucose tolerance, which may contribute to the increased vascula r morbidity and mortality reported in the condition. In these studies no in formation is available on oral glucose tolerance test (OGTT) timing in rela tion to administration of oral steroid and variable hydrocortisone doses we re employed. PATIENTS In order to assess glucose tolerance in patients treated with lowe r, more physiological doses, we performed a 75-g OGTT at least 1 month afte r hydrocortisone therapy was adjusted to 15 mg at 0800 h and 5 mg at 1700 h in 45 adult onset hypopituitary patients (30 M, 15 F). Mean (+/- SD) durat ion of hypopituitarism was 12 +/- 10 years, mean age 52 +/- 14 years and BM I 29.3 +/- 5.1 kg/m(2). All were on hydrocortisone, 43 on thyroxine, 31 on sex steroids, 9 on desmopressin and 33 had documented growth hormone defici ency. Hydrocortisone 15 mg was taken at 0800 and the OGTT commenced at 0900 . RESULTS Using standard WHO criteria 36 patients (80%) had normal glucose to lerance, 1 (2%) had newly diagnosed diabetes and 8 (18%) had impaired gluco se tolerance. Using the recently announced American Diabetes Association cr iteria for diagnosis 96% had normal glucose tolerance, 2% had diabetes and 2% impaired fasting glucose. CONCLUSION The markedly reduced prevalence of diabetes and impaired glucose tolerance on lower hydrocortisone replacement doses in our series of patie nts with hypopituitarism, not previously known to be diabetic, is of great interest. This lower prevalence may eventually result in reduced vascular c omplication rates.