32 subjects with long-term
insulin-dependent diabetes mellitus (
IDDM) were entered into a double-blind, randomised crossover trial with human and
porcine insulin. They were treated during both periods with
regular insulin and with
protamine (
NPH) insulin. 18 subjects started with human and 14 with
porcine insulin; the two
insulin periods each lasted twelve weeks; the
insulin doses were much the same in the two periods (mean 23 [SD 9] U daily NPH; 14 [7] U daily
regular insulin), as were
blood glucose profiles and HbA1c values. There were 171 episodes of hypoglycaemia during human and 150 episodes during
porcine insulin. Patients completed questionnaires after each hypoglycaemic episodes and at the end of the trial. Hunger and sweating without concomitant neuroglycopenic symptoms were significantly more frequent as initial warning symptoms during porcine than during human
insulin (41% vs 20%), whereas neuroglycopenic symptoms were more frequent during human
insulin. At the end of the trial 18 of 32 subjects reported diminished awareness of hypoglycaemia during human
insulin compared with 6 of 32 during
porcine insulin. Hypoglycaemia developed faster during human than during
porcine insulin administration. The transfer of
IDDM subjects from porcine to human
insulin seems to alter warning symptoms of low
blood glucose concentration, with consequent impairment of its early recognition.