This assay forms a part of the diagnosis and work up of precocious and delayed puberty in females. It is also useful in monitoring low dose female hormone replacemnt therapy in post menopausal women and for monitoring anti-estrogen therapy. This assay is useful for evaluating hypogonadism and oligomenorrhea in females. It assesses ovarian status including follicle development for in vitro fertilization. It evaluates feminization including Gynecomastia in males. All applications that require moderately sensitive measurement of estradiol: -Evaluation of hypogonadism and oligo-amenorrhea in females -Assessing ovarian status, including follicle development, for assisted reproduction protocols (eg, in vitro fertilization) -In conjunction with lutenizing hormone measurements, monitoring of estrogen replacement therapy in hypogonadal premenopausal women -Evaluation of feminization, including gynecomastia, in males -Diagnosis of estrogen-producing neoplasms in males, and, to a lesser degree, females -As part of the diagnosis and work-up of precocious and delayed puberty in females, and, to a lesser degree, males -As part of the diagnosis and work-up of suspected disorders of sex steroid metabolism, eg, aromatase deficiency and 17 alpha-hydroxylase deficiency -As an adjunct to clinical assessment, imaging studies and bone mineral density measurement in the fracture risk assessment of postmenopausal women, and, to a lesser degree, older men -Monitoring low-dose female hormone replacement therapy in post-menopausal women -Monitoring antiestrogen therapy