Additional testing is based on clinical suspicion: sexually transmitted infection (STI) testing in sexually active adolescents; thyroid function tests to rule out thyroid disorders; androgens and SHBG tests in patients with signs and symptoms of PCOS; prolactin levels test to check for hyperprolactinemia; FSH, LH, and estradiol measures to basically explore the HPO axis; and a Von Willebrand panel (vWF antigen level, ristocetin cofactor activity, and factor VIII activity) if a bleeding disorder is suspected [17,19,20,32]. Here, VWF is linked to sexually transmitted disease.