To date, their biological functioning has not been clarified, but recent evidence has pointed out how abnormal levels or activities [34] of many CA isoforms were associated with different diseases such as cancer (overexpression of CA IX/XII due to the hypoxia cascade activation), epilepsy (abnormal levels/activities of brain CA isoforms), and obesity (dysregulation of the mitochondrial isoforms CA VA/B) [42]. This evidence concerns the gene CA9 and obesity due to melanocortin 4 receptor deficiency.