An estradiol blood test from Walk-In Lab is typically ordered for women of reproductive age investigating fertility, and for the support of in vitro fertilization.The estradiol blood test is also known as E2, Estradiol-17β and estradiol assay. Fasting is not required when preparing for the assay, and results are delivered within one to two days. Walk-In Lab’s blood tests offer patients without a doctor’s order or without insurance, a confidential, convenient and cheap alternative.As the primary reproductive hormone (a steroid) in nonpregnant women, estradiol plays a critical role in both fetal and female secondary sexual characteristic development. During the normal menstrual cycle, thishormoneinfluencesuterusmaturationandmaintenance.Estradiol levels increase steadily during the follicular phase of the menstrual cycle, which is associated with ovarian follicle growth and development. As this process (known as the follicular phase) proceeds, estradiol exerts a negative feedback control on the pituitary gland, resulting FSH levels to drop. During the end of the follicular phase, estradiol levels drop dramatically and the hormone’s feedback on the hypothalamus turns positive, and produces the mid-cycle surge of LH (which immediately precedes ovulation). After ovulation, estradiol levels initially fall abruptly, and then increase as the corpus luteum forms. During the end of the cycle, estradiol levels taper off in anticipation of the initiation of the next follicular phase. The placenta produces the estradiol hormone during pregnancy, while during menopause, estradiol levels are generally low due to diminishedovarianproduction.Patients being treated with assisted reproductive techniques (in vitro fertilization) often have their estradiol levels measured to help monitor ovulation induction (to stimulate follicle development). Estradiol levels can be used to calibrate the exogenous gonadotropin administration and have been found to correlate with follicle size. The outcome of the ART protocol is predicted by the pattern of estradiol secretion during the cycle.Male testes produce small amounts of estradiol. Elevated levels of this hormone in males can lead to gynecomastia. Excessive consumption of alcohol, marijuana, prescription drugs such asphenothiazines and spironolactone, and increased body fat resulting in enhanced peripheral aromatization of androgens can lead to increased estradiol levels. Estradiol levels can also dramatically increase in germ cell tumors and tumors of a number of glands in both men and women.