Failure to suppress GH secretion after 2 weeks treatment with atropine or propanthelene in diabetics with proliferative retinopathy

Abstract. Complete suppression of GH secretion may halt the development of retinal new vessels in patients with diabetic proliferative retinopathy. We have investigated the effectiveness of two cholinergic antagonists, atropine and propanthelene given orally for 2 weeks, in suppressing 24-h GH and IGF-I levels. Seven insulin-dependent diabetics (3 males, 4 females; aged 22–34 years) with active proliferative retinopathy and 6 matched non-diabetic normal subjects were studied in random order with at least 2 weeks between treatments. Suppression of GHRH-induced GH release was demonstrated in both groups of subjects. Twenty-four hour GH secretion was not, however, suppressed in either the patient group (mean area under the GH curve mU·1 −1 ·h −1 ± sd ; baseline: 251 ± 108.7; after atropine: 174 ± 106.9; after propanthelene: 180 ± 72.4; P > 0.05) or in the control group (baseline: 103 ± 53.1; after atropine: 73 ± 83.6; after propanthelene: 122 ± 71.6; P >0.05). GH release at times of hypoglycemia was not suppressed. Mean IGF-I concentration was not significantly reduced. Two subjects (one patient and one control) could not tolerate atropine for more than one week. We conclude that repeated doses of atropine and propanthelene do not achieve complete 24-h GH suppression and are associated with a high incidence of unpleasant adverse reactions.