Blood Tests

Endocrine Testing

The female menstrual cycle is under the hormonal control of the endocrine system. This is a complex system of hormone signals and actions that involves the hypothalamus and pituitary gland (both a part of the brain essentially), as well as the ovaries.

Follicle Stimulating Hormone and Luteinizing Hormone

The hypothalamus releases gonadotropin releasing hormone (GnRH) which stimulates the pituitary gland to release follicle stimulating hormone (FSH) and luteinizing hormone (LH).

FSH and LH stimulate follicle production in the ovary. The hormones released by the ovary such as estradiol will eventually trigger a marked release of LH. This is known as the "LH Surge". This rise in LH will stimulate the rupture of the ovarian follicle and release of the oocyte into the abdominal cavity.

Women who are beyond the reproductive years or who have diminished ovarian function will lack the rise in estradiol and their FSH and LH will remain elevated. FSH is usually tested on day three of the menstrual cycle as an indicator of ovarian function.

This test is not necessary in everyone. Your physician will advise you if you need this test.

LH usually does not last very long in circulation and is therefore generally not tested. Urinary LH kits test for a form of LH that has an extended life span due to transformation in the urine. These kits are marketed for home testing for the rise in LH prior to ovulation.

With adequate monitoring in an infertility clinic you will not need to do urinary LH testing unless specifically directed by a physician or nurse practitioner.

Prolactin

Prolactin is another hormone of the endocrine system that is released from the pituitary gland. The pituitary is located at the floor of the brain just above the mouth and nasal passages.

Prolactin is responsible for the production of milk. Prolactin can hormonally interfere with the normal function of the hormones that govern follicular development and the menstrual cycle.

Prolactin tumors may also cause the pituitary to stop producing other hormones, including FSH and LH, which also have an impact on normal reproductive function.

Androgens

Androgens are a group of hormones usually thought of as male hormones; For example, testosterone is an androgen. But these hormones are also present in females.

There are several disorders in which the androgens are abnormally elevated in a female patient. Physical findings usually include abnormal hair growth, acne, and deepening of the voice.

One of the most common scenarios in which increased effects of androgens are seen is in polycystic ovarian syndrome.

Endocrine Insulin Resistance Screening

Current testing includes a 12-hour fast followed by a 75g glucola challenge (sugar solution commonly used to test for gestational diabetes in pregnancy). Blood work is drawn before the glucola (fasting) and at one and two hours after the glucola.

The blood is evaluated for insulin and glucose. Normally the fasting blood work will demonstrate a normal range glucose and a low insulin level. After a dose of sugar the blood glucose level increases as well as an increase in secreted insulin. Abnormal values can indicate insulin resistance, and in some cases, diabetes.

Insulin resistance is defined by a one hour post glucola insulin level greater than 23. Values below 23 are considered normal. These values may be different at different clinics or labs.

Glucose values over 200 at any point may indicate diabetes and further testing may be needed to confirm the diagnosis of diabetes. Often, patients with diabetes will have elevated fasting glucose levels, which again is evidence for diabetes.

Some investigators have reported a fasting glucose to insulin ratio is accurate enough to predict insulin resistance. Using this approach any fasting glucose to insulin ratio 4.5 or less is indicative of insulin resistance.

Progesterone

A progesterone drawn on day 21 -- or approximately seven days after the date of suspected ovulation -- can be an indicator of ovulatory function.

A level greater than eight usually indicates ovulation has occurred and adequate progesterone is being made to support an early pregnancy.

Thyroid Stimulating Hormone

Thyroid Stimulating Hormone (TSH) is released from the pituitary gland and stimulates the thyroid gland to make thyroid hormones. Like the thyroid exam, the TSH blood test may uncover a thyroid abnormality that may have an impact on fertility.

An elevated level means the gland is not making enough hormones, as in the case of hypothyroidism. Low levels indicate problems with TSH production or increased thyroid hormone production, known as hyperthyroidism.

Additional tests may be necessary to determine the exact cause of the abnormality which can be much more complex than presented here.