Blood hormone tests (called serum testing) has been one of the main methods used by most doctors to test hormones in the past. Because they are familiar and have been widely used, doctors feel as if more is known about blood test results and can receive those results quickly.  Being one of the most recognized tests by most insurance companies makes it more widespread than other testing methods.  There are, however, both pros and cons of blood hormone tests.

Blood Hormone Tests Pros

1.  It is a tried-and-true way to check hormones and is regarded by many to be an excellent approach. It is readily accessible, and has good correlation with symptoms.
2. “Serum Blood” tests are what your doctor sends you to the lab for. They measure hormone concentrations in to the serum or plasma part of the blood. Plasma is the watery, non-cellular portion of the blood from which cellular components such as red blood cells and white blood cells, are excluded.
3. Blood tests provide a snapshot of the total amount of hormone circulating in the bloodstream. It can be good for reproductive hormones:  testosterone, estrogens, and progesterone, as well as DHEA-S and estradiol.  Yearly blood tests of certain hormones can indicate negatively or positive trending changes as well as provide context for health and wellness problems. For example, research has indicated a relationship between lower levels of bio-available free testosterone and depression in men as well as correlations with diabetes, heart disease and Alzheimer’s. Unfortunately, if you don’t do regular blood tests it’s difficult to see your current results in relation to historical hormone levels. That is why it’s recommended to get these checked yearly.
4. Serum testing of hormones has long been accepted by the conventional medical community as the standard for measuring hormones. It has the advantage of being a relatively simple collection, requiring little patient involvement, and has very well-established reference ranges. Serum is ideal for testing peptide hormones such as FSH, LH, prolactin, fasting insulin, and thyroid hormones, including reverse T3, as well as thyroid antibodies. It is also used to measure sex hormone binding globulin (SHBG) and, less commonly, cortisol binding globulin (CBG).
5. Although some is bound, and some is free and ‘bio-available’ to show what the hormone does in the body, exact tissue bioavailability cannot be accurately measured. The amount of “free” hormones, however, can be measured. Laboratory scientists use a mathematical model to calculate bioavailability based on the level of total hormone, free hormone, percentage of free hormone, and circulating binding proteins that carry hormones in the blood. A free hormone is one that is not bound to carrier proteins.
6. Blood values are useful in monitoring peak levels of absorption of hormones, especially when someone is on hormone replacement therapies, or the normal metabolic lowest point achieved in the natural cyclic secretion of hormones. For example, if you want to see if you are absorbing testosterone from the application of a hormone cream or gel, you can measure your testosterone levels two hours after application.
7. For many doctors, blood tests are preferred for estradiol and other estrogens, testosterone and free testosterone, dihydrotestosterone, IGF-I, DHEA-Sulfate, cortisol, and thyroid hormones. A blood sample is also best for the pituitary hormones TSH, LH, and FSH.
8. One really good reason to use blood testing is that health insurances are more likely to cover it as an industry standard.

1.  Progesterone Blood Hormone Tests

• You can easily evaluate natural levels of estrogen or progesterone during their monthly peaks at mid luteal phase (either 7 days after ovulation, or 7 days prior to expected menses). This is when you’re most likely to catch the peak progesterone level.(typically days 18-22), though this does not apply to women past menopause who no longer have a period. This day will vary according to a woman’s cycle length however (for example, for a 28 day cycle, day 21 progesterone testing is appropriate; but for a 35 day cycle, progesterone would ideally be measured around day 28).  Though most hormones are tested for their total circulating level, many hormones can also be tested in blood in their free form.

• Progesterone measured by serum levels is mostly a measure of progesterone that is not going to be used by the body. A serum test can be used to compare one woman’s progesterone production to that of another woman, or to test how much progesterone is being made by a woman’s ovaries.

2.  Estrogen Blood Hormone Tests

• Blood testing does very well in assessing estradiol levels.  Estradiol (E2) is the female hormone most commonly measured in serum, although estrone (E1) is also available from many labs. Serum estriol (E3) testing, however, is not routinely performed. E3 is an important estrogen, generally considered protective because it binds to estrogen receptor beta (ERb), which is understood to increase differentiation and decrease proliferation of cells.

3.  Testosterone Blood Hormone Tests

• Blood serum testing can test both free (active) and total levels of testosterone. It can also be used to assess levels of sex hormone binding globulin (SHBG), which is important for maintaining reservoirs of sex hormones, as well as for protecting them from being excreted or metabolized too quickly. Serum testosterone is commonly available as both total and free, and therefore can be useful in assessing hormone balance.  For men, annual blood testing is important because it’s the only way to accurately measure PSA levels. Whether a man chooses to restore youthful hormone balance or not, annual PSA tests to assess the health of one’s prostate gland are vitally important.

• Recently the CDC launched a volunteer program for labs that has further advanced accuracy and reliability in blood testing. The CDC website (www.cdc.gov) shows the names of labs that have passed the performance criteria for the CDC Testosterone Reference Method in adult male and female serum.

4.  Cortisol Blood Hormone Tests

• Blood serum hormone tests are able to give you total cortisol results.

Blood Hormone Tests Cons

1. For sex hormones, serum testing has a more limited utility. There are several reasons for this. For most sex hormones, no distinction is made in serum between bound and free hormone. Estradiol, estrone, estriol, and progesterone are reported as total hormone and free hormones assays are not commonly available. This may lead to misleading results in which hormone levels appear to be normal or even high normal because of an abundance of bound hormone. However, if the free hormone level is low, the patient can be functionally deficient even with a normal total hormone level. It does not correlate with levels of the same hormone in the tissues, as it is unable to measure the bio-availability of the hormone.
2. Another limitation of serum hormones testing is the “snapshot” nature of single-point testing. Because hormones are secreted in a pulsatile manner over the course of the day (and night), it is difficult to know whether the levels in serum represent a peak, a valley, or something in between.  Sometimes more information is needed that can be helpful because of the daily/monthly rhythm of hormones.
3. Due to it’s ‘snapshot’ of hormones, it can present a difficulty in monitoring treatment for those doing bio-identical hormone replacement , as it is not possible to know whether today’s test was drawn at a similar point of hormone secretion as a previous test.
4. It does not evaluate age-related hormonal changes.

1.   Downside of Blood Hormone Tests for Progesterone

• Monitoring progesterone supple­mentation in serum also poses a problem. Transdermal progesterone does raise serum progesterone levels in a statistically significant manner, but the magnitude of change is quite small, which can lead to excessive dosing of progesterone as practitioners strive to achieve therapeutic levels in some opinion.

• Less than 20 percent of progesterone will be found in serum. It is obvious that serum levels would not detect the great majority of the progesterone added to whole blood.  The ovary-produced progesterone found in serum is also largely protein-bound. Protein-bound progesterone is not readily bioavailable to receptors in target tissues throughout the body. It is on its way to the liver to be excreted in bile. Only 2 to 5 percent of serum progesterone is “free” or non-protein-bound. This is the progesterone available to target tissues and to saliva.

2.  Downside of Blood Hormone Tests for Estrogen

• It is important to know that blood testing cannot easily be used to assess estrogen metabolites to provide a 2/16 hydroxyestrone ratio.  This ratio can be helpful since there are scientific studies that found some of the estrogen metabolites may promote cancer while others may have beneficial anticancer qualities.

• Blood testing cannot be used to check estriol levels. Since most bio-identical hormone replacement is typically done using a combination of estradiol and estriol, sometimes it is helpful to check both. However, for many women, an improvement in estradiol correlates with improvement in estriol so it is not necessary to test for estriol except in situations where the woman’s symptoms are not improving as expected.

3.  Downside of Blood Hormone Tests for Metabolites

• Serum hormone testing does not typically allow for the measurement of estrogen, androgen, and adrenal metabolites, which can provide a wealth of information to assist practitioners in understanding their patient’s condition and help to guide and fine-tune treatment options.  At this time the only available option for also testing metabolites is in the DUTCH test.

4.  Downside of Blood Hormone Tests for Cortisol

• Blood serum tests don’t provide free cortisol, metabolites or diurnal pattern.

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