Estradiol

Test ID: 

704207

CPT code:

82670

Clinical Use:

This estradiol assay is designed for the investigation of fertility of women of reproductive age and for the support of in vitro fertilization.

Test Information:

Estradiol plays a key role in germ cell maturation and numerous other, non−gender-specific processes, including growth, bone metabolism, nervous system maturation, and endothelial responsiveness.
The three major naturally occurring estrogens in women are estrone (E1), estradiol (E2), and estriol (E3). During menopause, a dramatic drop in E2 production leaves estrone as the predominant circulating estrogen. The concentration of E2 in men is much lower than in women of reproductive age. A lesser amount of E2 is produced in the adrenal glands and some peripheral sites, most notably adipose tissue. Most of the circulating estrone is derived from peripheral aromatization of androstenedione (mainly in the adrenal gland). E2 and E1 can be converted to each other, and both are inactivated via hydroxylation and conjugation.
Measurement of serum E2 serves an integral role in the assessment of reproductive function in females and in the assessment of infertility, oligomenorrhea, and menopausal status. E2 is commonly measured for monitoring ovulation induction, as well as during preparation for in vitro fertilization. Because of the relatively high serum concentrations of E2 in these patients, readily available automated immunoassay methods with modest sensitivity meet the clinical requirements.
Adult female. E2 levels are lowest during the early follicular phase and rise gradually. Two to three days before ovulation, estradiol levels start to increase much more rapidly to a peak just before ovulation. This dramatic increase in circulating E2 levels induces a surge in LH and FSH. E2 levels decline modestly during the ovulatory phase and then increase again gradually until the midpoint of the luteal phase and ultimately decline back to early follicular levels.
Assessment of E2 levels is useful for the evaluation of hypogonadism and oligomenorrhea in women. Measurement of gonadotropins (LH and FSH) is fundamental in differentiating these two low estradiol states. This can be caused by hypothalamic or pituitary failure due to conditions including multiple pituitary hormone deficiency and Kallmann syndrome. Diagnostic workup includes the measurement of E2, along with pituitary gonadotropins and prolactin and, possibly, imaging. This endocrine presentation can be caused by starvation, overexercise, severe physical or emotional stress, and drug/alcohol abuse.
Normal or high E2 with irregular or absent menstrual periods is suggestive of possible polycystic ovarian syndrome, androgen producing tumors, or estrogen producing tumors. In these cases, measurement of total and bioavailable androstenedione, dehydroepiandrosterone (sulfate), and sex hormone-binding globulin can aid in differential diagnosis.
A large population study (Randolph) found that the mean E2 level started to decline approximately two years prior to the final menstrual period (FMP) and exhibited a maximal rate of change at the FMP. A sensitive estradiol assay is required to measure E2 levels accurately in postmenopausal women. The current recommendations for postmenopausal female hormone replacement are to administer therapy in the smallest beneficial doses for as briefly as possible. Estrogen replacement in reproductive-age women should aim to mimic natural estrogen levels as closely as possible, while levels in menopausal women should be held near the lower limit of the premenopausal female reference range. Accurate measurement of E2 in women receiving hormone replacement may play a role in optimizing therapy.
In males, estradiol plays an important role in epididymal function and sperm maturation and is essential for normal spermatogenesis and sperm motility.
Gynecomastia is common during puberty in boys and can be seen in older males due to increased estrogen levels related to obesity (increased aromatase activity), decreased hepatic clearance, estrogen ingestion, and estrogen-producing tumors. Gynecomastia and other signs of male feminization may be caused by an absolute increase in E2 and/or E1. The testes may directly secrete too much estradiol due to a Leydig-cell or Sertoli-cell tumor. Alternatively, men with normal estrogen levels can develop gynecomastia, if testosterone levels are low due to primary/secondary testicular failure, resulting in an abnormally elevated estrogen:androgen ratio. Feminization may also occur in men treated with antiandrogen therapy or drugs with antiandrogenic effects (eg, spironolactone, digitalis). Conversely, individuals with elevated androgen levels will often exhibit gynecomastia caused by aromatase-catalyzed estrogen production.
Children and adolescents. A sensitive method is required to measure accurately the E2 concentrations found in boys and prepubertal girls.
E2 measurement in children suspected of having PP is performed to support the diagnosis and to determine the origin of the condition or disease. The source of increased estradiol can be exogenous estrogens or an ovarian cyst that has produced transient estrogens. Elevation of E1 or E2 alone suggests pseudoprecocious puberty, possibly due to a steroid-producing tumor. Persistently low estrogens and elevated gonadotropins in children with delayed puberty suggest primary ovarian failure, while low gonadotropins suggest hypogonadotrophic hypogonadism. The affected boys exhibit normal male sexual differentiation and pubertal maturation. However, boys with aromatase deficiency are typically extremely tall with eunuchoid proportions and continued linear growth into adulthood, severely delayed epiphyseal closure, and osteoporosis due to estrogen deficiency.

Specimen Type:

Serum

Requested Volume: 

0.8 mL

Minimum Volume: 

0.3 mL

Container Type: 

Red-top tube or gel-barrier tube

Collection:

If a red-top tube is used, transfer separated serum to a plastic transport tube.

Storage Instructions:

Room temperature

Stability Requirements:

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3

Rejection Criteria

Citrate plasma specimen; improper labeling

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