Estrogens are secreted in large amounts by the ovaries and, during pregnancy, by the placenta. Minute amounts are secreted by the adrenal glands and, possibly, by the testes. Estrogens induce and maintain the female secondary sex characteristics, promote growth and maturation of the female reproductive organs, influence the pattern of fat deposition that characterizes the female form, and cause early epiphyseal closure. They also promote retention of sodium and water by the kidneys and sensitize the myometrium to oxytocin.

Elevated estrogen levels are associated with ovarian and adrenal tumors as well as estrogen-producing tumors of the testes. Decreased levels are associated with primary and secondary ovarian failure, Turner's syndrome, hypopituitarism, adrenogenital syndrome, Stein-Leventhal syndrome, anorexia nervosa, and menopause. Estrogen levels vary in relation to the menstrual cycle.

Many different types of estrogens have been identified, but only three are present in the blood in measurable amounts: estrone, estradiol, and estriol. Estrone (E₁) is the immediate precursor of estradiol (E₂), which is the most biologically potent of the three. In addition to ovarian sources, estriol (E₃) is secreted in large amounts by the placenta during pregnancy from precursors produced by the fetal liver. Through radioimmunoassay, plasma levels of E₂ and E₃ can be determined. Total plasma estrogen levels are difficult to measure and are not routinely performed.

[Show Table Outline]

	Conventional Units	SI Units
Estradiol (E2)
Children under 6 yr	3-10 pg/mL	10-36 pmol/L
Adults Men	12-34 pg/mL	40-125 pmol/L
Adults Women (menstruating) Early cycle	24-68 pg/mL	90-250 pmol/L
Adults Women (menstruating) Midcycle	50-186 pg/mL	200-700 pmol/L
Adults Women (menstruating) Late cycle	73-149 pg/mL	250-550 pmol/L
Estriol (E3)
Weeks of pregnancy 30-32	2-12 ng/mL	7-40 nmol/L
Weeks of pregnancy33-35	3-19 ng/mL	10-65 nmol/L
Weeks of pregnancy 36-38	5-27 ng/mL	15-95 nmol/L
Weeks of pregnancy 39-40	10-30 ng/mL	35-105 nmol/L

[Table Outline]

• Estradiol (E₂)
• Estriol (E₃)

• In menstruating women, estrogen levels vary in relation to the menstrual cycle.
• Therapy with estrogen-containing drugs and adrenocorticosteroids will elevate levels, whereas clomiphene will decrease them.

• Infertility or amenorrhea of unknown etiology, with primary or secondary ovarian failure indicated by low estradiol (E₂) levels
• Establishment of the time of ovulation
• Evaluation of response to therapy for infertility
• Suspected precocious puberty with the disorder indicated by elevated estradiol (E₂) levels
• Suspected estrogen-producing tumors, as indicated by consistently high estradiol (E₂) levels without normal cyclic variations
• High-risk pregnancy with suspicion of fetal growth retardation, placental dysfunction, or impending fetal jeopardy, as indicated by decreased estriol (E₃) levels relative to the stage of pregnancy

Nursing Care Before the Procedure

Client preparation is the same as that for any study involving collection of a peripheral blood sample (see Appendix I).

• It is recommended that drugs known to alter estrogen levels be withheld for 12 to 24 hours before the test, although this practice should be confirmed with the person ordering the study.
• In menstruating women, the phase of the menstrual cycle should be ascertained, if possible. If the test is being conducted to detect ovulation, the client should be informed that it may be necessary to obtain a series of samples over a period of several days to detect the normal variation in estrogen levels.

A venipuncture is performed and the sample is collected in a red-topped tube. The sample should be handled gently to avoid hemolysis and transported promptly to the laboratory.

Nursing Care After the Procedure

Care and assessment after the procedure are the same as for any study involving the collection of a peripheral blood sample.

• Resume any medications withheld before the test.
• Complications and precautions: Assess increased or decreased levels in relation to age, gender, pregnancy, and menopausal status and in relation to associated levels of 24-hour urinary analysis and serum estradiol and estriol levels.