We report the treatment of a 14-year-old Indian boy with
acanthosis nigricans and hyperinsulinaemia with
metformin in an attempt to improve his skin lesions. Oral
metformin was used for 6 months with assessment of
insulin status during an intravenous
glucose tolerance test and hyperinsulinaemic-euglycaemic clamping before and
after treatment. The first-phase
insulin response reduced from 19,593 to 5,410 pmol/l/min (normal 1,900-13,400), and the second-phase
insulin response improved from 59,120 to 34,020 pmol/l/min (normal 2,900-18,100). During hyperinsulinaemic-euglycaemic clamping hepatic
glucose production was normally suppressed prior to
therapy, but peripheral
glucose remained abnormally low, 152 and 138% of basal (expected 199%). The
acanthosis nigricans remained unaltered but over this period puberty progressed and his body mass index increased. We conclude that, in this patient,
metformin had a minimal effect on the
hyperinsulinism and none on the
acanthosis nigricans in the relatively short term, but further studies in more patients over longer time intervals are warranted.