Diabetes and Endocrinology
Diagnostic tests
Blood tests
Depending on the nature of the disease, there are many different blood tests which can be requested to diagnose or confirm diagnosis. They may relate to thyroid profiles, menopause profile, infertility profiles, impotence profiles and many others.
Adrenal gland testing
Hydrocortisone day curve (HCDCT) and Cortisol day curve test (CDCT)
This test looks at your cortisol levels throughout the day. Cortisol is a steroid hormone which is produced by the adrenal glands and is vital for health. It has many functions which include helping to regulate blood pressure, helping to regulate the immune system, helping to balance the effect of insulin in regulating the blood sugar level, helping the body to respond to stress.
This test is most commonly used to test the blood levels of cortisol when taking hydrocortisone for adrenal insufficiency (Addison’s disease) but can also be used to check the natural blood levels of cortisol during the day.
Low dose dexamethasone suppression test (LDDST)
The LDDST is a test to see if you are producing too much of a hormone called cortisol. Cortisol is a steroid hormone which is produced by the adrenal glands and is vital for health. It has many functions which include helping to regulate blood pressure, helping to regulate the immune system, helping to balance the effect of insulin in regulating the blood sugar level, helping the body to respond to stress. The amount of cortisol that is made is controlled by another hormone called adreno-corticotrophic hormone (ACTH for short).
ACTH is made in the pituitary gland (a small gland that lies just under the brain). ACTH passes into the bloodstream, is carried to the adrenal glands, and ‘stimulates’ the adrenal glands to make cortisol. The LDDST works by giving you a short course of a steroid called dexamethasone. If everything is working normally this should cause your body to suppress the production of its own steroid hormone cortisol. If your levels of cortisol do not suppress after dexamethasone it may mean that your body is producing too much cortisol of its own (a disorder called Cushing’s syndrome).
Synacthen test
A synacthen test looks to see if your adrenal glands are producing enough of certain important hormones. A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. You have two adrenal glands. They are small glands, and lie just above each kidney. One of the hormones produced by the adrenal glands is cortisol. The amount of cortisol that is made is controlled by another hormone called adreno-cortico-trophic hormone (ACTH for short) which is made by the pituitary gland. ACTH passes through the bloodstream to the adrenal glands, and ‘stimulates’ the adrenal glands to make cortisol.
Cortisol is a steroid hormone and is vital for health. It has many functions which include helping to regulate blood pressure, helping to regulate the immune system, helping to balance the effect of insulin in regulating the blood sugar level, helping the body to respond to stress. When the adrenals fail to produce enough cortisol this is called Addison’s disease. A one-off measurement of blood cortisol is not good enough to diagnose Addison’s disease as it may be low from time to time in normal people. Therefore, if Addison’s disease is suspected, a syacthen test is usually needed to confirm the diagnosis. Synacthen is a form of ACTH stimulates the adrenal gland to mimic stress.
If the adrenals are normal, then blood samples taken shortly after this injection should show a rise in cortisol. If your adrenal glands are not working properly or are suppressed by your medications, you do not have an adequate rise in blood cortisol following the injection. A synacthen test is also used to diagnose congenital adrenal hyperplasia (CAH) when an adrenal hormone, 17 hydroxyprogesterone is measured with cortisol.
Glucagon stress test (GST)
A glucagon stress test looks to see if your body can make enough of certain important hormones when it is under stress and is an alternative to the Insulin Tolerance test. When things are working normally, your pituitary gland (a small gland that lies just behind the bridge of the nose) produces a several hormones. Two of these are: ACTH (adreno-cortico-trophic hormone) which stimulates your two adrenal glands to make cortisol.
Cortisol is a steroid hormone and is vital for health. It has many functions which include: helping to regulate blood pressure, helping to regulate the immune system, helping to balance the effect of insulin in regulating the blood sugar level, helping the body to respond to stress, and GH (Growth hormone) which has important effects on growth in childhood and influences adult body composition and the functioning of several body systems The glucagon stress test is used to test how much ACTH and cortisol you can produce and how much growth hormone is available when your body is stressed. The ‘stress’ in the test is an injection of a hormone called glucagon.
Pituitary gland testing
- Insulin tolerance test (ITT)
- Glucagon stress test (GST)
- Arginine stimulation test (GHRH)
An insulin tolerance test looks to see if your body can make enough of certain important hormones when it is under stress. A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. When things are working normally, your pituitary gland (a small gland that lies just behind the bridge of the nose ) produces a several hormones. Two of these are:
ACTH (adreno-cortico-trophic hormone) which stimulates your two adrenal glands (which sit just above the kidneys) to make cortisol. Cortisol is a steroid hormone and is vital for health. It has many functions which include helping to regulate blood pressure, helping to regulate the immune system, helping to balance the effect of insulin in regulating the blood sugar level, helping the body to respond to stress.
GH (Growth hormone) which has important effects on growth in childhood and influences adult body composition and the functioning of several body systems The insulin tolerance test is used to test how much ACTH and cortisol you can produce and how much growth hormone is available when your body is stressed. The ‘stress’ in the test is low blood sugar. This is caused by an injection of insulin, under very controlled conditions.
There are several ways to stimulate the pituitary gland. The insulin tolerance test causes a drop in blood sugar (mild hypoglycaemia) and you should not have this test if you have epilepsy, or ischaemic heart disease such as angina or a previous heart attack. Glucagon and the combination of GHRH and Arginine are alternative methods of stimulating the pituitary.
Growth hormone day curve test (GHDCT)
Growth Hormone is important for growth and bone strength when we are children. In adults too much growth hormone Your body may be producing too much or too little growth hormone of its own. The test looks at your growth hormone levels over a whole day, to confirm whether this is the case.
Oral glucose tolerance test with growth hormone levels (OGTT)
An OGTT with GH levels looks to see if your body is making too much of a hormone called growth hormone (GH). A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. GH is produced by your pituitary gland (a small gland that lies just under the brain.) GH has important effects on growth in childhood and influences adult body composition and the functioning of several body systems.
Measuring a single level of GH is not helpful as the body produces GH in pulses. GH tends to increase blood sugar and conversely, when things are working normally, a fixed dose of sugar by mouth lowers GH to undetectable levels. In acromegaly, the GH levels remain high (or may even increase) after a dose of sugar by mouth. This test looks at what happens to both your blood sugar levels and growth hormone levels after drinking a sugar solution.
Miscellaneous tests
Prolonged oral glucose tolerance test (POGTT)
An OGTT looks to see what happens to the sugar levels in your blood stream after you have had a fixed dose of sugar by mouth. This can give clues about symptoms that you may have experienced that could be caused by a low blood sugar. The test also provides information about your body’s production of a hormone called insulin. A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. Insulin is a hormone produced by the pancreas gland which acts on several body tissues to affect the uptake of sugar.
Water deprivation test (WDT)
Your kidneys are responsible for getting rid of body waste products dissolved in water. The amount of water lost from the kidneys (and the concentration of the urine) depend on a hormone called anti-diuretic hormone or ADH for short. A hormone is a chemical which is made in one part of the body but passes into the bloodstream and has effects on other parts of the body. ADH is made in the pituitary gland (a small gland that lies just under the brain).
ADH passes into the bloodstream, is carried to the kidneys, and controls the amount of water lost in urine or reabsorbed. If the pituitary gland is not producing enough ADH, or if the kidneys lose their sensitivity to ADH, you can lose excess water from the kidneys. This makes the urine very dilute and you tend to need to pass a lot of urine. This can then result in excessive thirst. A water deprivation test looks to see if the pituitary is producing enough ADH and if your kidneys can respond to ADH.