You have been referred to an endocrinologist, a doctor who specializes in the diagnosis and treatment of adult disorders caused by or affecting the endocrine glands. Endocrine glands release chemicals into the blood, which tell parts of the body to do certain jobs. These chemicals are referred to as hormones. Endocrine disorders are those that involve deficiencies or excesses of hormones. Therefore, growth hormone deficiency qualifies as an endocrine disorder. A growth hormone deficiency exists when there is not enough growth hormone in the body. In order for your doctor to make an accurate diagnosis, some testing may be necessary. This section was written to help you and your family understand the evaluation process of hormone deficiencies for adults.
Control of Hormones/ Hormone Deficiency
The hypothalamus controls the pituitary gland; both are located in the brain. The pituitary gland releases or controls many hormones in the body. The hormones are released in very small amounts into the bloodstream and then travel to parts of the body (referred to as target organs) to perform a specific job. These hormones control many of the body's functions, which are the following: Thyroid Stimulating Hormone (TSH) turns the thyroid gland "on" in order to control your metabolism. Adrenocorticotrophic hormone (ACTH) stimulates cortisol production to assist your body in daily function and stress. Vasopressin assists in the salt and water regulation of the body. Gonadotropins (FSH, LH) stimulate the ovaries (in women) or testes (in men) to release "sex" hormones (estradial or testosterone). Growth Hormone is released from the pituitary gland to cause growth in children and affects bone density, lipid metabolism, and muscle in children and adults.
Deficiencies of these hormones may occur alone or in combination with one or more other hormone deficiencies. The hormone(s) deficiency may be congenital, resulting from a defect in the brain. The deficiency may also be acquired, stemming from the damage to the brain after a sever head injury, serious illness (such as meningitis or encephalitis), brain tumor and/or radiation. Sometimes no cause for the hormone deficiency can be identified.
Evaluation/ Testing
In order to confirm or determine the possibility of hormone deficiencies your doctor will perform an examination and ask you some questions. Past records may have to be reviewed. Screening blood tests will usually be done. These blood tests will check the secretion of the pituitary hormones and their target organs.
Possible tests that may be done are listed:
- T4/TSH (to test thyroid function
- Cortisol FHS/LH (to test stimulation ability of the ovaries/testes)
- IGF-1 (an indirect measure of growth hormone)
- Electrolytes (measures water & salt balance)
- You may need to have a picture of the brain; this is done by a CT Scan or MRI. A CT scan gives a detailed picture of the brain using x-rays and a computer. A MRI gives a detailed picture of the brain using a magnet, radio waves and a computer. These tests are not painful but you will have to hold still for approximately one hour during the test.
Growth Hormone
If there is a possibility that you have growth hormone deficiency more testing will have to be performed. Growth hormone is secreted by the pituitary gland in quick bursts and does not last long in the blood, so checking a single blood sample for growth hormone will not be helpful. Deep sleep, vigorous exercise, and certain drugs are known to stimulate the secretion of growth hormone. The amount of growth hormone in the blood is measured by taking blood samples over a period of time. This is done by performing a "stimulation test." This refers to drawing baseline hormone levels, stimulating growth hormone release by giving a drug, and drawing intermittent growth hormone levels for one to three hours. The specifics of the tests, such as type of drug, length of test, and amount of the samples, will be determined by your doctor.
The doctor will need to make sure you are on adequate hormone replacement for other hormone deficiencies prior to stimulation testing. You will be given instructions. You should not have anything to eat or drink, except for water, after midnight the night before the test. You should have minimal activity before the test (no exercise that morning). An indwelling venous line (IV) will be started and baseline hormone levels drawn. You will be given a medication. The medication and its effects will be reviewed by your doctor or nurse. Growth hormone levels will be drawn intermittently from the IV at specified times for a period of two hours. If the IV stops working during the test, it is important that it be restarted so the samples may be obtained at the specified times.
The purpose of the testing is to determine if you are growth hormone deficient and/or eligible for growth hormone therapy. In order to start growth hormone treatment you will have one to two simulation tests performed. The number of tests will be decided by your doctor. Adults with peak growth hormone levels less than 3-5 mcg/L are identified as Growth Hormone Deficient. Please keep in mind that these numbers are not definitive; your doctor will make the final diagnosis. It may take several weeks for your doctor to receive and review the test results. You should discuss the results and the possibility of growth hormone therapy with your doctor.
Summary
Hormone replacement will be prescribed by your doctor if you are deficient in pituitary
hormones. Remember that each hormone has a specific function in your body, replacement medication is very important. If you have any questions don't hesitate to call your doctor, nurse, or the MAGIC Foundation for resources.
Contributed By:
Colleen Weber, R.N., B.S.N.
St. Louis, Missouri
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