Blood tests

Content Written By: Irwin Goldstein, MD

There are no universally agreed upon series of hormone blood tests that are considered relevant for the evaluation of women with sexual health concerns. This author has been evaluating sexual health problems in women for 12 years and based on clinical experience, routinely performs nine blood tests. These include: total testosterone, sex hormone binding globulin, dihydrotestosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), prolactin, estradiol, progesterone and thyroid stimulating hormone (TSH).

Total Testosterone and Sex Hormone Binding Globulin (SHBG)

The diagnosis of testosterone insufficiency in women is based on clinical symptoms of testosterone insufficiency syndrome and the biochemical demonstration of testosterone insufficiency. Symptoms of testosterone insufficiency most often reported include: a diminished sense of well-being or unpleasant mood; persistent, unexplained fatigue; and sexual function changes, including decreased libido, sexual receptivity, and pleasure. Other potential symptoms of testosterone insufficiency include bone loss and decreased muscle strength.

There is no universally accepted cut-off value of total testosterone that unambiguously defines the state of testosterone insufficiency syndrome. The diagnosis of testosterone insufficiency syndrome includes the presence of clinical symptoms, normal estrogen blood test values and a low blood test value for testosterone. Experts have agreed by consensus that a testosterone value at or below the lowest fourth of the normal range for the reproductive age (20 – 40 years) is considered to be low.

It should be noted that the various laboratory ranges currently considered normal for testosterone in women are not always reliable and are, at best, an approximation of testosterone status. Testosterone blood test values do not take into account the localized, tissue-specific metabolism of precursor androgens such as dehydroepiandrosterone (DHEA) into testosterone (intracrine mechanisms) or differences in androgen receptor sensitivity (for example CAG repeats polymorphisms) in which the response of target organs to a given testosterone blood level will vary in different individuals.

Abnormal total testosterone values alone are not sufficient reason to institute therapy. In women with minimal symptoms of testosterone insufficiency syndrome and markedly reduced testosterone values, a discussion should ensue with the woman concerning risks and benefits of testosterone replacement therapy.

In women, total testosterone values fall normally with age usually starting at age 30. There is only minimal change in testosterone throughout the day but there are elevations in testosterone in association with the menstrual cycle. The highest levels of testosterone occur just prior to ovulation. Thus the ideal time to clinically measure total testosterone in pre-menopausal women not on hormonally-based contraceptives is mid-cycle.

Furthermore, total testosterone measurements can be misleading because only unbound testosterone can act within cells to directly synthesize critical proteins that affect the structure and function of hormonally sensitive tissues such as the clitoris and vagina, as well as the brain, bones, skeletal muscle, skin, breast, sweat glands, skeletal muscle, and fat.

In normal females, 1-2% of testosterone is free (unbound). Of the testosterone that is bound, approximately 60% is bound to sex hormone–binding globulin (SHBG) with high affinity, and the remainder is bound with much lower affinity to albumin and other proteins. High values of SHBG, such as induced by oral contraceptive pill use, will lower the unbound physiologically available testosterone, thus SHBG, in part, regulates testosterone function. It is clinically relevant in each woman suspected of having testosterone insufficiency syndrome to be aware of the SHBG value.

Another option is to determine the calculated free testosterone value by measuring total testosterone (ng/dl), SHBG (nmol/l), and albumin (g/dl) concentrations. These three values can determine calculated free testosterone with a calculator available on the webpage of the International Society for the Study of the Aging Man (ISSAM) (www.issam.ch/freetesto.htm). In most healthy women the albumin value can be assumed to be 4.3g/dl, however when a women has a chronic medical disorder it is advisable to determine the woman’s actual albumin value.

A calculated free testosterone value less than 0.5ng/dl is considered abnormal. Actually, in a study of sexually functional women age 20 – 40 years, the calculated free testosterone values ranged from 0.6 – 0.8 ng/dl. Calculated free testosterone values are clinically useful to help confirm testosterone insufficiency syndrome, especially in women with elevated SHBG values.

There are other clinically available blood tests available. Antibody-based, free testosterone assays are considered unreliable. Bioavailable testosterone measures free and albumin-bound fractions of testosterone, and is reliable and accessible.

Dihydrotestosterone

Serum dihydrotestosterone (DHT) determination may be valuable because androgen-dependent functions involve the conversion of testosterone to DHT via the enzyme 5-alpha reductase. Obtaining baseline DHT values may be clinically relevant to help resolve the relationship of side effects such as acne or scalp hair loss to the testosterone replacement therapy. If the baseline level of DHT is low and the post-testosterone treatment level of DHT is high, then the acne and/or hair loss is likely related to the testosterone treatment. Supraphysiologic levels of DHT may be successfully managed with low doses of 5-alpha reductase enzyme inhibitors such as 1 mg finasteride once a week. A full discussion of the risks and benefits of 5-alpha reductase enzyme inhibitors needs to occur in pre-menopausal women. If the baseline and post-testosterone DHT values are not changed, then the troubling side effect such as scalp hair loss is less likely to be related to testosterone treatment.

Prolactin

Hyperprolactinemia is an uncommon cause of testosterone insufficiency syndrome and female sexual dysfunction. Determination of serum prolactin is recommended if a woman presents with signs and symptoms of hypoactive sexual desire disorder (HSDD) and has biochemical evidence of testosterone insufficiency (normal estrogen blood test values and a low testosterone value at or below the lowest fourth of the normal range for the reproductive age (20 – 40 years), or a calculated free testosterone value less than 0.5ng/dl). Although rare, elevated serum prolactin levels are associated with adenomas of the pituitary.

Estradiol

Estradiol or 17β-estradiol is the predominant sex hormone present in women. Estradiol represents the major estrogen hormone; the other estrogens include estrone and estriol. Estradiol has a critical impact on sexual functioning, but also affects numerous other estrogen dependent organs including the brain, muscle, liver, hair, skin and bone. Estradiol is eventually formed through the metabolism of testosterone by the enzyme aromatase. During the reproductive years, estradiol is synthesized in the ovary. Smaller amounts of estradiol are also produced by the adrenal gland and estradiol is additionally produced in the periphery, especially in fat cells.

Estrogen, like testosterone, progesterone and thyroid hormone directs the synthesis of critical proteins that affect the structure and function of multiple organs.

Serum estradiol measurement in pre-menopausal women with sexual dysfunction reflects primarily the activity of the ovaries. In the normal menstrual cycle, estradiol levels measure typically <50 pg/ml at menstruation, rise with follicular development, drop briefly at ovulation, and rise again during the luteal phase for a second peak. At the end of the luteal phase, estradiol levels drop to their menstrual levels. Estradiol values will vary from <50 to approximately 500 pg/ml throughout the cycle.

Serum estradiol measurement in peri-menopausal or menopausal women with sexual dysfunction also reflects primarily the activity of the ovaries and the state of estrogen synthesis. In menopause, estradiol values will fall below <50 pg/ml. One study showed that such estradiol values are consistent with significantly higher numbers of women complaining of vaginal dryness and bothered by the problem, pain during sexual activity, pain with penetration, burning during penetration than women with estradiol values greater than 50 pg/ml. A rational goal of treatment is to maintain serum estradiol values above 50 pg/ml and below 100 pg/ml.

Thyroid stimulating hormone.

For successful sexual function, thyroid function should be normal. Thyroid hormones, similar to estrogen, progesterone and testosterone hormones, act on cells to direct the synthesis and release of various proteins. These hormone-mediated proteins are responsible for structure and function of many tissues, including genital tissues. Female genital tissues, similar to other tissues in the body, depend upon thyroid hormone for regulation of cell metabolism. For example, thyroid hormone acts on clitoral and vaginal smooth muscle cells to improve the responsiveness of the smooth muscle. The tone of the smooth muscle in the clitoris and vagina determines the state of sexual arousal. Clitoral and vaginal smooth muscle cells relax during sexual arousal to allow for blood to engorge the tissues. The health of the smooth muscles cells is, in part, determined by the action of the thyroid hormone.
A history consistent with thyroid disorders is obtained during the medical evaluation. Hypothyroidism symptoms are non-specific and may include: fatigue and weakness, weight gain or increased difficulty losing weight, coarse, dry hair and dry, rough pale skin, hair loss, intolerance to cold and/or inability to tolerate the cold like others, muscle cramps and frequent muscle aches, sexual dysfunction, constipation, depression, irritability, memory loss, abnormal menstrual cycles, and sexual dysfunction.
Hyperthyroidism symptoms are non-specific and may include: feeling hotter than others around you, losing weight even if eating more, fatigue at the end of the day but often having trouble sleeping, trembling of the hands, a hard or irregular heartbeat or palpitations, irritability and a tendency to become easily upset.

Both hyperthyroidism and hypothyroidism have been shown to adversely affect sexual function. In examining the clinical and hormonal profiles of patients, blood test screening is best performed by obtaining a thyroid stimulating hormone (TSH) value. TSH values should be between 0.4 - 5.5 mIU/L. Values of TSH below 0.4 mIU/L are consistent with hyperthyroidism. Values of TSH greater than 5.5 mIU/L are consistent with hypothyroidism. Contemporary patient management would consider earlier treatment of hypothyroidisn at TSH values greater than 3.5 mIU/L versus waiting for the TSH to rise to 5.5 mIU/L. Should the diagnosis of hypothyroidism or hyperthyroidism be considered, further blood tests such as free T4, free T3, total T4 and total T3 may be obtained.

Luteinizing hormone (LH) and Follicle stimulating hormone (FSH)

Serum luteinizing hormone (LH) and follicle stimulating hormone (FSH) determinations are of value in women with female sexual dysfunction. Both hormones are synthesized and secreted by the pituitary gland. LH acts on the ovary to synthesize increasing amount of androgens and hormonal precursors for estradiol production. FSH stimulates the maturation of the ovarian follicle and is involved in ovulation.

In pre-menopausal women, LH and FSH will vary widely from 1-20 IU/L. Low FSH and LH values are seen in women on oral contraceptives. Other conditions include amenorrhea and eating disorders anorexia and bulimia. Women on infertility therapy or endometriosis therapy using drugs such as lupron also have low FSH and LH values.

High LH and FSH levels are seen in menopause. Increased LH and FSH are also seen in premature menopause and oophorectomy. LH is elevated and FSH is lowered specifically in polycystic ovary syndrome.

Progesterone

Progesterone is a progestogen steroid hormone involved in sexual function. Progesterone, like estrogen, causes critical proteins to be synthesized that among other roles, regulates sexual behavior. The role of progesterone in sexual performance is well described in animals but less appreciated in humans.

Progesterone is found in high concentrations in certain areas in the brain and affects nerve functioning, improves memory and cognitive ability. Progesterone is better understood for its role in the menstrual cycle, and in pregnancy. Progesterone prepares the uterine lining for implantation and also thickens vaginal lining and cervical mucous. Normal menstrual bleeding is progesterone-withdrawal bleeding.

If a women is receiving estrogen replacement and the women has a uterus, it is imperative to provide progesterone to prevent endometrial thickening and potential endometrial carcinoma.

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