Medical Terminology: Endocrine Tests

1. What are Endocrine Tests?
The endocrine system transports hormones via blood vessels to regulate bodily functions, including metabolism, growth, mood, and tissue function. Hormones are created, stored, and released by glands and act as messengers, signaling other glands and organs to react in a specific manner.
Hormones are released based on existing hormone levels in the blood to maintain hormonal levels in balance. For example, an excess amount of a hormone may cause the release of a different hormone that causes the gland to stop or reduce excretion of the hormone, thereby bringing hormones in balance.
Diseases can alter the release of hormones, resulting in underproduction or overproduction of one or more hormones. Endocrine tests are administered to assess if the patient is experiencing an endocrine disease.

2. Adrenocorticotropic Hormone (ACTH) and Cortisol Test
The adrenocorticotropic hormone (ACTH) and cortisol test is used to assess the function of the pituitary gland and the adrenal glands.

Understanding the Adrenocorticotropic Hormone and Cortisol Test
The hypothalamus releases corticotropin-releasing hormone (CRH), which causes the pituitary gland to release the ACTH. Adrenocorticotropic hormone causes the adrenal gland to release cortisol. Cortisol increases blood pressure and glucose and reduces the immune responses. The ACTH test measures the level of ACTH in the blood. ACTH levels fall when cortisol levels rise, and ACTH level rise when cortisol levels fall.
The health care provider may request that an inferior petrosal sinus sample be taken from the inferior petrosal sinus near the pituitary gland to determine if the pituitary gland is producing ACTH or if ACTH is made elsewhere in the patient’s body.

3. Overnight Dexamethasone Suppression Test
The overnight dexamethasone suppression test is used to assess the function of the adrenal glands and screen for Cushing’s syndrome.

Understanding the Overnight Dexamethasone Suppression Test
The pituitary gland releases ACTH whenever there is a low level of cortisol in the blood. ACTH signals the adrenal glands to release cortisol. An adrenal gland tumor causes the release of cortisol in the absence of ACTH.
Dexamethasone is a medication similar to cortisol such that dexamethasone signals the pituitary gland that there is a high level of cortisol in the blood, causing the pituitary gland to suppress the release of ACTH.
The overnight dexamethasone suppression test examines the patient’s cortisol level after dexamethasone is administered. The cortisol level should be lower because there is no ACTH in the blood to signal the adrenal glands to release cortisol. If cortisol levels remain high, then this is a sign of Cushing’s syndrome as a result of an adrenal gland tumor producing cortisol.

4. Aldosterone Blood Test
The aldosterone blood test is used to screen for an adrenal gland tumor, an overactive adrenal gland, and the underlying cause of high blood pressure and low potassium levels in the blood.

Understanding the Aldosterone Blood Test
Kidneys release renin. Renin is a hormone that signals the adrenal glands to release aldosterone to control blood pressure and fluid and electrolytes balance by retaining fluid and sodium. The aldosterone test determines the level of aldosterone in the blood. This test is typically performed with the renin activity test.

5. Cortisol Blood Test
The cortisol blood test is used to assess the function of the pituitary and adrenal glands.

Understanding the Cortisol Blood Test
Cortisol, produced by the adrenal glands, is a hormone that causes an increase in blood pressure and an increase in glucose while decreasing the immune response. Cortisol levels reach their highest at 7. a.m. and their lowest 3. hours after sleep, which is based on the diurnal rhythm. However, the diurnal rhythm reverses if the patient works at night and sleeps during the day.
The pituitary gland releases ACTH whenever there is a low level of cortisol in the blood. ACTH signals the adrenal glands to release cortisol.
The health care provider may also order the dexamethasone suppression test, the adrenocorticotropic hormone test, or a 24-hour urine test.

6. Estrogen Blood Test
The estrogen blood test is used to assess the effect of fertility therapy and screen for abnormal sexual characteristics in men, estrogen-producing tumors, and fetal birth defects.

Understanding the Estrogen Blood Test
Estrogen is a hormone produced in the ovaries, placenta, muscle tissue, adipose tissue, adrenal glands, and testicles in men. There are three types of estrogen hormones:
. Estradiol: Estrogen found in nonpregnant women that varies with the menstrual cycle.
. Estriol: Estrogen that is produced by the placenta and is measured in pregnant women who are in at least the ninth week of pregnancy.
. Estrone: Estrogen measured in women who have finished menopause, and in both men and women suggested of having testicular cancer, ovarian cancer, or adrenal gland tumor.
Estrogen levels can also be measured in urine. The health care provider may order a triple test or quad marker screen to assess for fetal birth defects. The maternal serum triple test measures levels of estrogen, alpha-fetoprotein (AFP), and human chorionic gonadotropin (hCG). The quad marker screen measures the same as the triple test, but also tests inhibit A hormone.

7. Growth Hormone (GH) Test
The growth hormone (GH) test is used to screen for abnormal growth and for pituitary gland tumors and to assess treatment.

Understanding the Growth Hormone Test
The human GH, secreted by the pituitary gland, stimulates cell growth and reproduction and growth factor 1. (IGF-1). The growth hormone test measures the level of growth hormone in blood.
The health care provider may order the growth factor 1. (IGF-1) test, the growth hormone suppression test (glucose loading test), and the growth hormone stimulation test (insulin tolerance test), along with the GH test.

8. Luteinizing Hormone (LH) Test
The luteinizing hormone (LH) test is used to assess the underlying cause of infertility or the effectiveness of infertility treatment, the underlying cause of irregular menstrual periods, or amenorrhea. In addition, this test also screens for menopause, the underlying cause of erectile dysfunction, and precocious and delayed puberty.

Understanding the Luteinizing Hormone Test
Luteinizing hormone is produced by the pituitary gland, which stimulates production of testosterone and ovulation, and regulates the menstrual cycle. Home ovulation testing kits detect LH levels in urine.

9. Parathyroid Hormone (PTH) Test
The parathyroid hormone (PTH) test is used to assess the underlying cause of abnormal calcium levels in the blood and screen for hyperparathyroidism.

Understanding the Parathyroid Hormone Test
The parathyroid glands release PTH when there is a low calcium level in the blood, causing the kidneys to retain calcium and bone to release calcium into the blood. Parathyroid hormone converts vitamin D to an active form, resulting in increased absorption of calcium by the intestine. Calcium and phosphorus have an inverse relationship. When the calcium level in blood is high, the phosphorus level in blood is low. Therefore, PTH also controls the phosphorus level in blood. The PTH test measures the level of PTH in blood.
The health care provider may also order tests for calcium and phosphorus levels in the blood and creatinine tests to assess kidney function.

10. Thyroid Hormone Test
The thyroid hormone tests are used to screen for hyper- and hypothyroidism and assess the treatment.

Understanding the Thyroid Hormone Tests
The hypothalamus gland releases thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary gland to release thyroid-stimulating hormone (TSH). Thyroid-stimulating hormone causes the thyroid gland to release thyroxine (T4) and triiodothyronine (T3), both of which regulate metabolism. T4. and T3. are produced only if there is sufficient iodine in the thyroid gland. T4. and T3. are transported in blood either freely or bound to globulin. Free T4. and T3. affect metabolism. The thyroid gland also releases calcitonin when the patient has hypercalcemia. Calcitonin regulates calcium levels in the blood by moving calcium from the blood to bone. The thyroid hormone tests measure the levels of T4. and T3. in the blood. There are four thyroid hormone tests:
. Total Thyroxine (T4): This test measures the amount of T4. hormone that is bound to globulin and the amount of unbound T4. hormone, called free thyroxine, in the blood.
. Free Thyroxine (FT4): This test measures the amount of unbound T4. hormone.
. Free Thyroxine Index (FTI): This test compares the amount of bound thyroxine to total thyroxine, and thereby indirectly measures unbound thyroxine.
. Triiodothyronine (T3): This test measures T3. hormone that is bound to globulin and the amount of unbound T3. hormone called free triiodothyronine.

11. Thyroid-Stimulating Hormone (TSH) Test
The thyroid-stimulating hormone (TSH) test is used to screen for hyper- and hypopituitarism and hypothalamus disorder. In addition, it is also used to screen for the underlying causes of hyper-and hypothyroidism and assess their treatment.

Understanding the Thyroid-Stimulating Hormone Test
The hypothalamus gland releases thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary gland to release TSH. Thyroid-stimulating hormone causes the thyroid gland to release thyroxine (T4) and triiodothyronine (T3), both of which regulate metabolism. The TSH test measures the level of TSH in the blood.
The health care provider will likely order thyroid hormone tests along with the TSH test.

12. Testosterone Test
The testosterone test is used to screen for the underlying causes of infertility, erectile dysfunction, osteoporosis in men, hirsutism in women, and irregular menstruation. It is also used to assess for precocious puberty in boys and assess treatment for prostate cancer.

Understanding the Testosterone Test
The pituitary gland releases luteinizing hormone that stimulates the release of testosterone by the adrenal glands, testes, and ovaries. Testosterone is unbound in blood, called free or bound to the sex hormone–binding globulin (SHBG) protein in blood. The testosterone test measures the level of testosterone in blood.

Basic Questions
Endocrine Tests

1. How do hormones work?
Hormones are created, stored, and released by glands and act as messengers signaling other glands and organs to react in a specific manner.

2. What is the purpose of the adrenocorticotropic hormone (ACTH) and cortisol tests?
The ACTH and cortisol tests are used to assess the function of the pituitary and adrenal glands.

3. What is the relationship between adrenocorticotropic hormone (ACTH) and cortisol?
ACTH levels fall when cortisol levels rise, and ACTH level rise when cortisol levels fall.

4. What is the impact of high cortisol levels in blood?
Cortisol increases blood pressure and glucose and reduces the immune responses.

5. What is the purpose of the overnight dexamethasone suppression test?
The overnight dexamethasone suppression test is used to assess the function of the adrenal glands and screen for Cushing’s syndrome.

6. What is dexamethasone?
Dexamethasone is medication similar to cortisol in which dexamethasone signals to the pituitary gland that there is a high level of cortisol in the blood, causing the pituitary gland to suppress the release of ACTH.

7. What should happen when dexamethasone is administered?
The cortisol level should be lower because there is no ACTH in the blood to signal the adrenal glands to release cortisol. If cortisol levels remain high, this is a sign of Cushing’s syndrome as a result of an adrenal gland tumor producing cortisol.

8. Why is the aldosterone blood test administered?
The aldosterone blood test is used to screen for an adrenal gland tumor, an overactive adrenal gland, and the underlying cause of high blood pressure and low potassium levels in the blood.

9. What is the relationship between aldosterone and renin?
Kidneys release renin. Renin is a hormone that signals the adrenal glands to release aldosterone to control blood pressure and fluid and electrolyte balance by retaining fluid and sodium.

10. Why is the estrogen blood test ordered?
The estrogen blood test is used to assess the affect of fertility therapy and screen for abnormal sexual characteristics in men, estrogen-producing tumors, and fetal birth defects

11. What is estradiol?
Estradiol is estrogen found in nonpregnant women that varies with the menstrual cycle.

12. What is estriol?
Estriol is estrogen that is produced by the placenta and is measured in pregnant women who are in at least the ninth week of pregnancy.

13. What is estrone?
Estrone is estrogen measured in women who have finished menopause, and in both men and women suggested of having testicular cancer, ovarian cancer, or an adrenal gland tumor.

14. Why might a health care provider measure growth hormone (GH)?
The GH test is used to assess treatment for abnormal growth and screen for abnormal growth and a pituitary gland tumor.

15. Where is GH secreted?
The human GH, secreted by the pituitary gland, stimulates cell growth and reproduction and growth factor 1. (IGF-1).

16. What is the purpose of the luteinizing hormone (LH) test?
The LH test is used to assess the underlying cause of infertility or the effectiveness of infertility treatment, the underlying cause of irregular menstrual periods, or amenorrhea. It is also used to screen for menopause, the underlying cause of erectile dysfunction, and precocious and delayed puberty.

17. What is the function of (LH)?
Luteinizing hormone is produced by the pituitary gland, which stimulates the production of testosterone and ovulation and regulates the menstrual cycle.

18. Why would a health care provider order the parathyroid hormone (PTH) test?
The PTH test is used to assess the underlying cause of an abnormal calcium level in the blood and screen for hyperparathyroidism.

19. What is the relationship between the PTH and calcium level in the blood?
The parathyroid glands release PTH when the calcium level in the blood is low, causing the kidneys to retain calcium and bone to release calcium into the blood. Parathyroid hormone converts vitamin D to an active form, resulting in increased absorption of calcium by the intestine.

20. How does the PTH control the phosphorus level in the blood?
Calcium and phosphorus have an inverse relationship. When the calcium level in the blood is high, the phosphorus level in the blood is low. Therefore, PTH also controls the phosphorus level in the blood.

21. Why is the thyroid hormone test administered?
The thyroid hormone test is used to screen for hyper- and hypothyroidism and assess for their treatment.

22. What is the relationship between the hypothalamus gland and the thyroid gland?
The hypothalamus gland releases thyrotropin-releasing hormone (TRH), which stimulates the anterior pituitary gland to release thyroid-stimulating hormone (TSH). Thyroid-stimulating hormone causes the thyroid gland to release thyroxine (T4) and triiodothyronine (T3), both of which regulate metabolism.

23. What is the function of calcitonin?
The thyroid gland also releases calcitonin when the patient has hypercalcemia. Calcitonin regulates calcium levels in the blood by moving calcium from the blood to the bone.

24. Why might the health care provider order the thyroid-stimulating hormone (TSH) test?
The TSH test is used to screen for hyper- and hypopituitarism and hypothalamus disorder. It is also used to screen for the underlying causes of hyper- and hypothyroidism and assess their treatment.

25. What is the relationship between luteinizing hormone (LH) and testosterone?
The pituitary gland releases LH, which stimulates the release of testosterone by the adrenal glands, testes, and ovaries.