PLOD1 and precocious puberty: This scale evaluates the risk of bias in observational studies by assessing the selection of study groups (maximum four points), the comparability of the groups (maximum two points: one point for comparable age and one point for comparable basal LH values), and the outcome of interest, which was predefined as the incidence of central precocious puberty: the early onset of secondary sexual characteristics in girls before the age of eight (maximum three points) [13,18-33].