Cushing's Awareness: Testing

What I want to do today is outline basic tests that most endocrinologists use for the diagnosis of Cushing's. The following chart may help understand why certain tests are run:


This chart is talking about the comparision of serum cortisol and plasma ACTH to known ranges for known times. Serum cortisol should be measured at 8 a.m., 4 p.m., and around midnight (most clinical studies use 11 p.m. - 1 a.m.). If you remember, this will show the diurnal variation (or lack thereof). If the diurnal rhythm is not normal, this is one clue for the diagnosis of Cushing's.
According to Esoterix Labs, normal adult ranges for serum cortisol are:

• 8:00 a.m. 8.0 – 19 ug/dL
• 4:00 p.m. 4.0 - 11 ug/dL
• midnight close to zero

ACTH is pulsatile, and should be 9-54 pg/mL during the day. At midnight, however, the clinical studies say it should be less than 23 pg/dL or it is excessive. Refer back to "When tests don't even rate an A+ or a C-" to see how to make sure ACTH is tested properly. Often, it's hard to get a valid result.

In The Biochemical Investigation of Cushing Syndrome[Neurosurg Focus 16(4), 2004. © 2004 American Association of Neurological Surgeons], the last page says:

In patients with Cushing disease, 50% have a 9 a.m. plasma ACTH level within the normal reference range of 9 to 54 pg/ml (2–12 pmol/L) and the remaining patients have a slightly elevated ACTH level.[36] Due to the loss of circadian rhythm, however, nighttime ACTH secretion is abnormal. A midnight plasma ACTH levelgreater than 23 pg/dl (5 pmol/L) confirms the presence of an ACTH excess.

Salivary cortisol tests are also done to determine diurnal/circadian rhythm. Since midnight serum cortisols are more difficult to do because the patient has to go to an open lab late at night, salivary kits offer a much easier alternative. However, serum cortisol tests tend to work better for cyclical patients because the serum level has to be pretty high before the cortisol is readable in saliva. Esoterix has developed a more sensitive assay for testing salivary cortisol which may offer a comparable output.

There are four FDA-approved labs for testing salivary cortisol (Quest, ACL Labs, Esoterix, and Labcorp), and each uses it's own method with varying ranges. The ranges for Esoterix are below:


24-hr Urinary Free Cortisol (UFC) is another test that is used. Again, depending on the method used to run these and the lab, the ranges can vary. I also discussed these in "When tests don't even rate an A+ or a C-" . These are used to get an average value of the excess cortisol secreted in a 24-hour period.

Some researchers also use a 10-hour UFC to see if excess is just secreted overnight. These are analyzed differently by looking at the cortisol/creatinine ratio. A ratio of 15 or higher is considered diagnostic.

There is some question about the validity of the dexamethasone suppression test, with various factions in the literature and in the research saying various things. Basically, it boils down to the dosage used with the dexamethasone and the doctor doing it.

An Update on the Overnight Dexamethasone Suppression Test for the Diagnosis of Cushing's Syndrome: Limitations in Patients with Mild and/or Episodic Hypercortisolism [T. C. Friedman, Exp Clin Endocrinol Diabetes. 2006 Jul;114(7):356-60] says:

The objective of this study was to determine the sensitivity of the one mg overnight dexamethasone suppression test in patients with mild and/or periodic Cushing's syndrome...
Therefore, an overnight dexamethasone suppression test was performed in 17 consecutive patients presenting to an endocrinology clinic with signs and symptoms of hypercortisolemia who were later proven to have Cushing's syndrome...
[These patients] failed to suppress to a value less than this cut-off point (sensitivity of 41 %). These results demonstrate that the great majority of patients with mild and/or periodic Cushing's syndrome suppress to overnight dexamethasone. Since patients with mild and/or periodic Cushing's syndrome are the patients in whom the identification of hypercortisolism is difficult, our results from this relatively small study suggest that this test should no longer be used to exclude these patients from further workup for Cushing's syndrome.

DO NOT LET A DOCTOR TELL YOU THAT YOU DO NOT HAVE CUSHING'S BASED ON THE RESULT OF JUST ONE OR EVEN A FEW "NORMAL" TESTS!! In this post, I explained the difficulties in diagnosing cyclic/episodic/mild/subclinical Cushing's. Be prepared to do a lot of testing. If you are cyclic, you will have to figure out the symptoms of your "highs" versus your "lows". The only way to do that is to JOURNAL your symptoms and TEST! Keep very detailed records of all lab results. Make sure you get a copy of each. Compare the results to your symptoms. If you are consistent, you can figure out your cycle fairly quickly. In order to do this, you must find a doctor who is willing to let you test when you need to test.

Cushing's Awareness: Growth Hormone Levels

Ok...what's the big deal, anyhow? Why would anyone need to have their growth hormone levels evaluated? I'm going to stick to adults today because low growth hormone (GH) is a whole 'nuther ballgame with children.

As a review, growth hormone is secreted by the pituitary gland. Some pituitary tumors secrete too much GH which causes gigantism in children and acromegaly in adults. However, on the flip side, some tumors suppress the pituitary and too little is secreted. Even if the tumor does not do that, surgery to remove a tumor may cause the pituitary to quit or lessen it's secretion of GH. Radiation is also used on pituitary tumors that cannot be totally removed or if there is hyperplasia, and it, too, can damage the pituitary.

Adult Growth Hormone Deficiency (GHD) is a very real problem. GH maintains a healthy balance of muscle, bones, and fat and if an adult is deficient, her body composition changes. The body has less muscle, visceral fat is deposited around the abdomen, and bones weaken. Other fats in the body are affected. "Good" cholesterol (HDL) decreases but "bad" cholesterol (LDL) increases. This is very hard on the cardiovascular system (remember, the heart is a muscle) and the cerebrovascular system.

In Diagnosis of adult GH deficiency [V. Gasco, et al, Pituitary (2008) 11:121–128], the authors state:

Adults with growth hormone deficiency (GHD) have impaired health, which improves with GH replacement. GHD in adults leads to impairment in body composition and function, as well as to deranged lipoprotein and carbohydrate metabolism and increased cardiovascular morbidity. Based on evidence that GHD in adults is a
new syndrome which may benefit from GH replacement, health authorities in many countries have approved the therapeutic use of GH in hypopituitaric patients with severe GHD.

Not only is the physical health of a GHD adult affected. Social isolation, excessive tiredness, anxiety, depression, and apathy are also symptoms of GHD.

Growth hormone secretion is pulsatile which means random measurements of GH levels are not helpful or diagnostic. Since insulin-like growth factor-1(IGF-1) is stimulated by GH but does not fluctuate during the day like GH, it is useful in monitoring GH levels. Low levels are an excellent indication of a GHD problem. However, normal levels do not mean there is no deficiency.

The Growth Hormone Research Society met in 2007 in Australia and penned a consensus statement about the problems, testing, and treatments associated with adult GHD. In their consensus statement, they write:

...the patient with objective evidence of hypothalamic–pituitary disease (e.g., on imaging or after irradiation), who may present with organic isolated GHD as the first hormonal deficiency...may account for up to 25% of cases of GHD in the adult.

Consensus guidelines for the diagnosis and treatment of adults with GH deficiency II[European Journal of Endocrinology (2007) 157 695–700]

In this same consensus statement, they say:

Not all patients suspected of having GHD,however, require a GH stimulation test for diagnosis.Patients with three or more pituitary hormone deficiencies and an IGF-I level below the reference range have a 97% chance of being GHD, and therefore do not need a GH stimulation test.

The Insulin Tolerance Test has, in the past, been the "gold-standard" for measuring true GHD. However, there have been some problems with its reproducibility and specificity.

In Clinical Presentation and Diagnosis: Growth Hormone Deficiency in Adults the American Journal of Managed Care [Volume 10:S424-S430 , October 2004 , Number 13 Suppl ] states:

Numerous pharmacologic agents can be used to assess GH production and secretion
by the pituitary in adults (Table 3). These include insulin, arginine, levodopa
(L-dopa), arginine plus L-dopa, arginine plus GHRH, and the glucagon test. None
display perfect sensitivity and specificity; however, the insulin tolerance test
(ITT) and arginine-GHRH are excellent tests.

The arginine-GHRH test was used by major pituitary centers around the world. It was less stressful with less risk for the patient but yielded reproducible and accurate results.  However, it is now difficult if not impossible to find GHRH because the company which produced it is no longer doing so.  Now, glucagon is the major agent with the ITT the least preferable option.  The ITT side effects are numerous, and are potentially hazardous.  It is labor intensive.   If one has a history of seizures, hypothyroidism, panhypopituitarism or heart disease, it is not advisable to use that method. (See here.)

What are the differences in these two tests? In the ITT, the pituitary is provoked to produce GH by causing hypoglycemia in the patient with insulin. With the Glucagon stim test, glucagon is a peptitide hormone which essentially does the same thing.  Why glucagon causes release of GH is unclear, at least according the the article linked.

Cushing's Awareness: Pituitary hormones and disorders

Endocrine disorders usually involve a lot of testing, I thought I would spend some time the next few days talking about some of those tests. With Cushing's Disease, an adenoma can cause hypopituitarism and panyhypopituitarism as well as excess secretion of a hormone or hormones from the adenoma itself. In order to understand what tests are done and why you will first need to know more about the pituitary and disorders associated with it.

Hypopituitarism is a disorder where the pituitary does not secrete enough or any of one or more hormones. The literature varies on this, however. Some define it as "two or more hormones". However, the bottom line is the patient is deficient and this will affect one or more of the bodies functions. Panhypopituitarism, on the other hand, is the deficiency and/or total loss of all hormone production in the pituitary.

The pituitary gland is a bean-shaped (think lima bean) organ that is at the base of the brain. The gland anterior lobe, the intermediate lobe, the posterior lobe. The intermediate lobe is rudimentary in human beings but produces several hormones whose physiologic significance is only now being established.
The pituitary is attached to the hypothalumus (a part of the brain that affects the pituitary gland) by nerve fibers. The pituitary gland itself consists of three sections:

Anterior lobe:

• growth hormone
• prolactin - to stimulate milk production after giving birth
• ACTH (adrenocorticotropic hormone) - to stimulate the adrenal glands
• TSH (thyroid-stimulating hormone) - to stimulate the thyroid gland
• FSH (follicle-stimulating hormone) - to stimulate the ovaries and testes
• LH (luteinizing hormone) - to stimulate the ovaries or testes

Intermediate lobe:

• MSH(melanocyte-stimulating hormone)- to control skin pigmentation

Posterior lobe:

• ADH (antidiuretic hormone) - to increase absorption of water into the bloodby the kidneys
• oxytocin - to contract the uterus during childbirth and stimulate milk production. It is also believed to be important for orgasm

Each of these hormone levels can tell a diagnostician a lot about the state of the pituitary and what may be happening there. The level of each is like a piece of the puzzle, and some need to be measured regularly to get the overall picture.

Not only are these hormone levels important, but the levels of other hormones affected by these are measured. In the thyroid, TSH from the pituitary affects the levels of T3 and T4.

In the adrenal gland, the level of cortisol is affected by the level of ACTH.  It's that feedback loop I'm

always talking about. The level of cortisol at various times of the day (8 a.m., 4 p.m., and midnight) is an important tool for diagnosing Cushing's.  See "When Cortisol is a Night Owl" for more on this.

In post-pubescent females, FSH acts on the ovarian follicles to produce estrogens and LH is instrumental in the production of progesterone. In males, LH is instrumental in the production of testosterone. The hypothalamus secretes gonadotropin-releasing hormone (GnRH) to the pituitary gland in pulses. These, in turn, stimulate the pituitary gland to secrete luteinizing hormone (LH) which then stimulates the Leydig cells of the testes to produce testosterone.

Link

That brings us to the hypothalamus. The hypothalamus is a region of the brain above the pituitary. It contains several types of neurons responsible for secreting different hormones. These are released into the blood in the capillaries and travel to the anterior lobe of the pituitary.

• Corticotropin-releasing hormone (CRH)
• Thyrotropin-releasing hormone (TRH)
• Growth hormone-releasing hormone (GHRH)
• Gonadotropin-releasing hormone (GnRH)
• Dopamine
• Somatostatin

Each of these plays a role in the production of the hormones in the pituitary. Usually, those pituitary hormones are tested rather than the hypothalamic hormones. The hypothalamic hormones are often used to stimulate the pituitary to see if it is producing those anterior lobe hormones, so they are valuable in the testing process.

Altogether, these glands and their hormones comprise the Hypothalamic-Pituitary-Adrenal axis, also known as the HPA-axis. I have not touched on the adrenal hormones, yet, except to mention cortisol.
I will get there.

Cushing's Awareness: Heritable Cushing's

There are several forms of known heritable Cushing's.    The most well-known is MEN1. Carney Complex is also fairly well understood.  The least studied, and newest researched is FIPA.

MEN1:   (Multiple endocrine neoplasia, Type 1)  According to Medscape, "the combination of parathyroid tumors, pancreatic islet cell tumors, and anterior pituitary tumors is characteristic of MEN1. Although usually inherited as an autosomal dominant disorder, MEN1 can also occur sporadically (without a family history) as a result of new mutations. It is also important to keep in mind that family members of an MEN1-affected individual may have been undiagnosed at the time of death. Patients with untreated MEN1 have a decreased life expectancy, with a 50% probability of death by age 50 years."

Carcinoid tumors can occur in patients with MEN1 and are located in the bronchi, gastrointestinal tract, pancreas, and thymus. In men, especially smokers, the thymus is most often affected. Thymic carcinoids[8] associated with MEN1 are often nonfunctional and aggressive. In women, bronchial carcinoids are most common. Carcinoids can actively secrete hormones such as serotonin, somatostatin, corticotropin, and growth hormone.

Carney Complex:  Two genes have been associated with Carney complex. They are called PRKAR1A and CNC2. It is believed that about 60% of people with Carney complex have a mutation in the PRKAR1A gene and up to 6% may have deletions in this gene.There may be other genes associated with Carney complex, and studies are ongoing to learn more about it.  It is an autosomeal dominant disease.

Fewer than 500 cases of Carney Complex have been reported. It is estimated that between 50% and 70% of cases of Carney complex run in families. The other percentage occurs by chance and may be due to a new gene mutation.

FIPA:  (Familial isolated pituitary adenoma) This is an inherited condition characterized by development of a pituitary adenoma. FIPA can be caused by mutations in the AIP gene which is thought to act as a tumor suppressor.  According to this FIPA site, "about 1 in 20 pituitary tumours do seem to run in families. If the condition only seems to affect the pituitary gland in the family, then the disease is known as Familial Isolated Pituitary Adenoma (FIPA). "  It is an autosomal dominant disease with incomplete penetrance (not all patients who carry the abnormal gene will develop the disease).

There are also several mutations which occur to cause Cushing's, some very recently discovered. I'll talk about those next time.

Cushing's Awareness: Types of Tumors

Just how many kinds of tumors are there associated with Cushing's? Wait, are we talking about pituitary tumors? Or adrenal tumors? How about ectopic tumors? Are you beginning to get the picture of why this illness is so hard to diagnose?

PITUITARY TUMORS/ADENOMAS:

So, let's talk about tumors. These are also sometimes called adenomas. Pituitary adenomas are classified several ways. They may be classified by pathology, by size, and by hormone production. I'm going to keep it simple here and list the basic types of tumors by the hormones they produce. Bear in mind that many pituitary adenomas produce more than one hormone. This production is not held in check by the body's normal feedback loops, thus they aren't controlled.

• Corticotroph (ACTH-Producing) Adenomas :  The corticotroph adenoma secretes adrenocorticotropic hormone (ACTH), which results in Cushing Disease because it stimulates the adrenal glands to overproduce cortisol. These tumors are initially confined to the sella turcica, but they may enlarge and become invasive especially after bilateral adrenalectomy. This is called Nelson's Syndrome.
• Somatotroph (GH-Producing) Adenomas:  Somatotroph adenomas produce growth hormone (GH), resulting in gigantism in younger patients and acromegaly in adults. These tumors may also extend beyond the sella.
• Thyrotroph (TSH-Producing) Adenomas:  Thyrotroph adenomas secrete thyroid-stimulating hormone (TSH), also known as thyrotropin, which results in hyperthyroidism without TSH suppression. Many are large and invasive and typically have other types of adenoma cells included, such as ACTH and/or GH.
• Lactotroph (PRL-Producing) Adenomas:  Lactotroph adenomas secrete prolactin (PRL) and are typically an intrasellar tumor. However, they can become large enough to enlarge the sella turcica.
• Nonfunctioning (Endocrine-Inactive) Adenomas:  These tumors cause symptoms when they extend beyond the sella, which results in pressure on the surrounding structures such as optic nerves and carotid veins. They are not associated with clinical and biochemical evidence of hormone excess.
• Carcinomas:  Pituitary carcinomas, although extremely rare, are usually endocrinologically functional, and ACTH-producing and PRL-producing tumors are the most frequent.

ADRENAL TUMORS/ADENOMAS:

When a tumor in an adrenal gland overproduces hormones, the tumor is called a functioning tumor. A tumor in an adrenal gland that does not produce hormones is, understandably, called a nonfunctioning tumor. A tumor can start in an adrenal gland (called a primary adrenal tumor) or it can begin in another organ, such as the lungs, and then metastasize (spread) to the adrenal glands. I'm going to focus on primary adrenal gland tumors.

• Adenoma:  An adenoma is a benign nonfunctioning tumor of the adrenal cortex. Also called an adrenocortical adenoma, this tumor usually does not cause symptoms, and, if it is small, may not require any treatment. However, as it grows it can put pressure on parts of the gland causing it to under or overproduce hormones. The cause of adrenal adenomas is unknown, but the current accepted theory is that they arise because of mutations in certain genes. Adrenal adenomas are more common in some inherited diseases, including multiple endocrine neoplasia type I, Beckwith-Wiedemann syndrome and the Carney complex.
         Chronic adrenal stimulation by ACTH leads to bilateral adrenocortical hyperplasia and, if long-standing, nodular transformation according to recent research. Thus, an ACTH producing tumor of the pituitary or ectopic tumor may stimulate the adrenals to form tumors or become hyperplastic (more about hyperplasia in a bit).
• Adrenocortical carcinoma:  Although exceedingly rare this is the most common type of malignant adrenal gland tumor, affecting the cortex, also called an adrenal cortical carcinoma. Adrenocortical carcinoma can be a functioning or nonfunctioning tumor. If the tumor is functioning, it may produce more than one hormone.
• Pheochromocytoma:  A pheochromocytoma is a rare tumor that develops in the core of an adrenal gland. It secretes excessive amounts of catecholamines, usually epinephrine and norepinephrine.
• Neuroblastoma:  Neuroblastoma is a disease in which malignant cells form in nerve tissue of the adrenal gland. It is very rare.
• Rest Tissue:  An island of adrenal cortical tissue separate from the adrenal gland, usually found in the retroperitoneal tissues, kidney, or genital organs.

If that isn't enough, there is another form of tumor that isn't a tumor. It's called hyperplasia. These tumor cells may invade the pituitary or the adrenals in nests throughout the gland.

Pituitary hyperplasia is defined as "a non-neoplastic increase in one or more functionally distinct types of pituitary cells. The acini, though expanded, remain intact", according to www.hormones.gr/123/article/article.html .

Adrenal hyperplasia, simply put, is enlargement of the adrenal glands due to Cushing's.  It may be due to increased stimulation by the pituitary gland or for other reasons. 

Cushing's Awareness: Subclinical Cushing's

Subclinical Cushing's Disease/Syndrome has be a controversial diagnosis.  Only in the past decade has the term been used.  According to Pathophysiology and treatment of subclinical Cushing’s disease and pituitary silent corticotroph adenomas  “subclinical has been used in the pituitary. Subclinical Cushing’s disease is defined by ACTH-induced mild hypercortisolism without typical features of Cushing’s disease."  This places the cause of subclinical Cushing's with the pituitary.

The authors of Clinical Cushing’s syndrome: Current concepts and trends define subclinical Cushing's as coming from an adrenal incidentaloma.

Initial diagnostic evaluation of a patient with an adrenal incidentaloma aims to determine the functional status of the mass and the possibility of malignant disease. The vast majority of these lesions are benign nonhypersecreting cortical neoplasms. However, a significant percentage of cases present subclinical hormonal activity, mainly concerning glucocorticoid secretion.4-6 Subtle cortisol hypersecretion by adrenal incidentalomas is characterized by alterations of the hypothalamic-pituitary-adrenal (HPA) axis due to adrenal autonomy in the absence of the typical clinical phenotype of hypercortisolism, a disorder that has been defined as subclinical Cushing’s syndrome. (Underlining is mine.)

Late-Night Salivary Cortisol for Diagnosis of Overt and Subclinical Cushing’s Syndrome in Hospitalized and Ambulatory Patients also indicates subclinical as having a pituitary origin.   But Subclinical Cushing's syndrome also indicates an adrenal incidentaloma as the source.  It goes on to say, "Patients with subclinical Cushing's syndrome lack the classical stigmata of hypercortisolism but have a high prevalence of obesity, hypertension, and type 2 diabetes."  (I thought those were classical symptoms of Cushing's.)

Subclinical Cushing's Disease is considered to be an epidemic disease. It has a prevalence of 0·2–2 per cent in the adult population, alone.  (Systematic review of surgical treatment of subclinical Cushing's syndrome)  However, there is no definite criteria for diagnosing it.  Most use the dexamethasone suppression test as a frontline test, but the cut-off criteria for subclinical Cushing's have not been standardized.  Subclinical Cushing's is also sometimes called "mild" Cushing's by some.

The article,  High Prevalence of Normal Tests Assessing Hypercortisolism in Subjects with Mild and Episodic Cushing’s Syndrome Suggests that the Paradigm for Diagnosis and Exclusion of Cushing’s Syndrome Requires Multiple Testing, states:

We have recently described poor sensitivity of a single overnight dexamethasone test in detecting hypercortisolism in patients with mild or episodic Cushing’s syndrome [37]. Thus, our data suggest that current screening tests performed once are inadequate to detect or exclude hypercortisolism in patients with mild or episodic Cushing’s disease.

If there are such epidemic numbers of subclinical Cushing's, seems to me these learned folks need to get together and figure this out.

Cushing's Awareness: Relative Terms used to Define the "Severity" of Cushing's Disease

There are several terms floated about in the literature/research about Cushing's Disease which try to indicate the severity of the disease.  Here, I want to talk about and try to define the terms, then will later post about each so that I can talk about the research involved in each.

1. Florid:  Also termed"classical", it shows evidence of continual or almost continual hypercortisolism. There is a school of thought which says these are really very rapidly cycling forms of Cushing's. However, there does not seem to be a consensus on that in the literature and in the research.
2. Cyclical:  This refers to elevated cortisol levels present at regular intervals.  The diurnal pattern is often reversed at regular intervals.   In Cyclic Cushing syndrome: definitions and treatment implications,  the authors state, "one will observe periodic episodes of “normal” test results. The duration of the cycles has been described as being 12 hours to 86 days".
3. Subclinical:  This is defined by ACTH-induced mild hypercortisolism without typical features of Cushing’s disease, according to this Japanese research.
4. Mild:  patients with Cushing’s syndrome whose cortisol tests were sometimes elevated and sometimes normal, according to this research.  Dr. Friedman, et al, believe episodic and mild Cushing's occur together.
5. Episodic:  According to Friedman's research, linked above, episodic refers to "elevated cortisol levels occurring without any temporal pattern."