Gestational diabetes mellitus and impaired glucose tolerance in an aged Macaca mulatta.

Gestational diabetes mellitus was diagnosed in an aged (21-year-old) pregnant rhesus monkey (Macaca mulatta); she was hyperglycemic and had minimal glucose clearance in an intravenous glucose tolerance test (iv-GTT). An overweight (840 g) dead full-term fetus was delivered by cesarean section. A second iv-GTT conducted 3 months later revealed impaired glucose tolerance. While pregnant, the monkey was hyperinsulinemic and showed minimal secretory response to the glucose load. When tested postpartum, the fasting insulin was only slightly elevated, but the insulin response to glucose was still lacking.