INSL3 as a Biomarker of Pubertal Activation: Role in Evaluating Precocious and Delayed Puberty

This is an observational study in children up to 16 years old who are suspected of having central precocious puberty or delayed puberty. The main questions it aims to answer are: * Can the level of insulin-like peptide 3 (INSL3) predict if a child's puberty has truly started? * Can this marker help reduce the need for more complex and invasive tests? Participants will: * Give one extra blood sample just before starting the standard gonadotropin-releasing hormone (GnRH) stimulation test (during the baseline blood draw). * Have this extra sample used to measure the INSL3 hormone. * Complete the rest of the GnRH test as prescribed by their doctor. Researchers will compare the INSL3 hormone levels in children who have a positive GnRH test to those who have a negative test. This will help researchers learn if INSL3 can be used as a new, simple tool to diagnose early or delayed puberty.