CYP19A1 and obesity due to melanocortin 4 receptor deficiency: The relationship between low TT and obesity- and lipid-related abnormalities is currently unclear, but possible mechanisms are discussed below: First, previous studies suggested that low TT was due to increased aromatase activity in adipose tissue and increased conversion of TT to E2, which inhibits the hypothalamic-pituitary-gonadal (HPG) axis, but several more recent studies have found a positive correlation between TT and E2 (50), and our study also had similar findings (P< 0.001).