PRKAA2 and obesity due to melanocortin 4 receptor deficiency: Given that metformin is highly efficacious against type 2 diabetes, it is also interesting to note that AMPK deficiency93, PPHN94–96 and pulmonary hypertension of the adult97,98 are associated with obesity and type 2 diabetes (maternal with PPHN), not least because similar signs and symptoms are present even where no such comorbidity is evident99–101.