If one of these tests shows a deficiency of hormones produced by the pituitary, magnetic resonance imaging (MRI) scan of the pituitary is the first step in identifying an underlying cause. MRI may show various tumors and may assist in delineating other causes. Tumors smaller than 1 cm are referred to as "microadenomas", and larger lesions are called "macroadenomas". Computed tomography with radiocontrast may be used if MRI is not available. Formal visual field testing by perimetry is recommended, as this would show evidence of optic nerve compression by a tumor.

Other tests that may assist in the diagnosis of hypopituitarism, especially if no tumor is found on the MRI scan, are ferritin (elevated in hemochromatosis), angiotensin converting enzyme (ACE) levels (often elevated in sarcoidosis), and human chorionic gonadotropin (often elevated in tumor of germ cell origin). If a genetic cause is suspected, genetic testing may be performed.

The diagnosis of hypopituitarism is made on blood tests. Two types of blood tests are used to confirm the presence of a hormone deficiency: basal levels, where blood samples are taken–usually in the morning–without any form of stimulation, and dynamic tests, where blood tests are taken after the injection of a stimulating substance. Measurement of ACTH and growth hormone usually requires dynamic testing, whereas the other hormones (LH/FSH, prolactin, TSH) can typically be tested with basal levels. There is no adequate direct test for ADH levels, but ADH deficiency can be confirmed indirectly; oxytocin levels are not routinely measured.

Generally, the finding of a combination of a low pituitary hormone together with a low hormone from the effector gland is indicative of hypopituitarism. Occasionally, the pituitary hormone may be normal but the effector gland hormone decreased; in this case, the pituitary is not responding appropriately to effector hormone changes, and the combination of findings is still suggestive of hypopituitarism.

Currently, in the United States and over 40 other countries, every child born is screened for 21-hydroxylaase CAH at birth. This test will detect elevated levels of 17-hydroxy-progesterone (17-OHP). Detecting high levels of 17-OHP enables early detection of CAH. Newborns detected early enough can be placed on medication and live a relatively normal life.

The screening process, however, is characterized by a high false positive rate. In one study, CAH screening had the lowest positive predictive value (111 true-positive cases among 20,647 abnormal screening results in a 2-year period, or 0.53%, compared with 6.36% for biotinidase deficiency, 1.84% for congenital hypo-thyroidism, 0.56% for classic galactosemia, and 2.9% for phenylketonuria). According to this estimate, 200 unaffected newborns required clinical and laboratory follow-up for every true case of CAH.

The best diagnostic tool to confirm adrenal insufficiency is the ACTH stimulation test; however, if a patient is suspected to be suffering from an acute adrenal crisis, immediate treatment with IV corticosteroids is imperative and should not be delayed for any testing, as the patient's health can deteriorate rapidly and result in death without replacing the corticosteroids.

Dexamethasone should be used as the corticosteroid if the plan is to do the ACTH stimulation test at a later time as it is the only corticosteroid that will not affect the test results.

If not performed during crisis, then labs to be run should include: random cortisol, serum ACTH, aldosterone, renin, potassium and sodium. A CT of the adrenal glands can be used to check for structural abnormalities of the adrenal glands. An MRI of the pituitary can be used to check for structural abnormalities of the pituitary. However, in order to check the functionality of the Hypothalamic Pituitary Adrenal (HPA) Axis the entire axis must be tested by way of ACTH stimulation test, CRH stimulation test and perhaps an Insulin Tolerance Test (ITT). In order to check for Addison’s Disease, the auto-immune type of primary adrenal insufficiency, labs should be drawn to check 21-hydroxylase autoantibodies.

Screening for hypothyroidism is performed in the newborn period in many countries, generally using TSH. This has led to the early identification of many cases and thus the prevention of developmental delay. It is the most widely used newborn screening test worldwide. While TSH-based screening will identify the most common causes, the addition of T testing is required to pick up the rarer central causes of neonatal hypothyroidism. If T determination is included in the screening done at birth, this will identify cases of congenital hypothyroidism of central origin in 1:16,000 to 1:160,000 children. Considering that these children usually have other pituitary hormone deficiencies, early identification of these cases may prevent complications.

In adults, widespread screening of the general population is a matter of debate. Some organizations (such as the United States Preventive Services Task Force) state that evidence is insufficient to support routine screening, while others (such as the American Thyroid Association) recommend either intermittent testing above a certain age in both sexes or only in women. Targeted screening may be appropriate in a number of situations where hypothyroidism is common: other autoimmune diseases, a strong family history of thyroid disease, those who have received radioiodine or other radiation therapy to the neck, those who have previously undergone thyroid surgery, those with an abnormal thyroid examination, those with psychiatric disorders, people taking amiodarone or lithium, and those with a number of health conditions (such as certain heart and skin conditions). Yearly thyroid function tests are recommended in people with Down syndrome, as they are at higher risk of thyroid disease.

Genetic analysis can be helpful to confirm a diagnosis of CAH but it is not necessary if classic clinical and laboratory findings are present.

In classic 21-hydroxylase deficiency, laboratory studies will show:

Classic 21-hydroxylase deficiency typically causes 17α-hydroxyprogesterone blood levels >242 nmol/L. (For comparison, a full-term infant at three days of age should have <3 nmol/L. Many neonatal screening programs have specific reference ranges by weight and gestational age because high levels may be seen in premature infants without CAH.) Salt-wasting patients tend to have higher 17α-hydroxyprogesterone levels than non-salt-wasting patients. In mild cases, 17α-hydroxyprogesterone may not be elevated in a particular random blood sample, but it will rise during a corticotropin stimulation test.

Diagnosis is made first by diagnosing Cushing's syndrome, which can be difficult to do clinically since the most characteristic symptoms only occur in a minority of patients. Some of the biochemical diagnostic tests used include salivary and blood serum cortisol testing, 24-hour urinary free cortisol (UFC) testing, the dexamethasone suppression test (DST), and bilateral inferior petrosal sinus sampling (BIPSS). No single test is perfect and multiple tests should always be used to achieve a proper diagnosis. Diagnosing Cushing's disease is a multidisciplinary process involving doctors, endocrinologists, radiologists, surgeons, and chemical pathologists.

Once Cushing's syndrome has been diagnosed, the first step towards finding the cause is measuring plasma corticotropin concentrations. A concentration consistently below 1.1 pmol/L is classified as corticotropin-independent and does not lead to a diagnosis of Cushing's disease. In such cases, the next step is adrenal imaging with CT. If plasma corticotropin concentrations are consistently above 3.3 pmol/L, then corticotropin-dependent Cushing's syndrome is most likely. Any intermediate values need to be cautiously interpreted and a corticotropin-releasing hormone (CRH) test is advised in order to confirm corticotropin dependency. If corticotropin-dependent Cushing's syndrome is determined then the next step is to distinguish between Cushing's disease and ectopic corticotropin syndrome. This is done via a combination of techniques including CRH, high-dose DST, BIPSS, and pituitary MRI.

Two dexamethasone suppression tests (DSTs) are generally used, the overnight and 48-h DSTs. For both tests, a plasma cortisol level above 50 nmol/L is indicative of Cushing's disease. However, 3-8% of patients with Cushing's disease will test negative due to a retention of dexamethasone suppression abilities. For non-Cushing or healthy patients, the false-positive rate is 30%. The 48-h DST is advantageous since it is more specific and can be done by outpatients upon proper instruction. In the high-dose 48-h DST, 2 mg of dexamethasone is given every 6 hours for 48 hours or a single dose of 8 mg is given. This test is not needed if the 48-h low-dose DST has shown suppression of cortisol by over 30%. These tests are based on the glucocorticoid sensitivity of pituitary adenomas compared to non-pituitary tumors.

Administration of corticotropin releasing hormone (CRH) can differentiate this condition from ectopic ACTH secretion. In a patient with Cushing's disease, the tumor cells will be stimulated to release corticotropin and elevated plasma corticotropin levels will be detected. This rarely occurs with ectopic corticotropin syndrome and thus is quite useful for distinguishing between the two conditions. If ectopic, the plasma ACTH and cortisol levels should remain unchanged; if this is pituitary related, levels of both would rise. The CRH test uses recombinant human or bovine-sequence CRH, which is administered via a 100μg intravenous bolus dose. The sensitivity of the CRH test for detecting Cushing's disease is 93% when plasma levels are measured after fifteen and thirty minutes. However, this test is used only as a last resort due to its high cost and complexity.

A CT or MRI of the pituitary may also show the ACTH secreting tumor if present. However, in 40% of Cushing's disease patients MRI is unable to detect a tumor. In one study of 261 patients with confirmed pituitary Cushing's disease, only 48% of pituitary lesions were identified using MRI prior to surgery. The average size of tumor, both those that were identified on MRI and those that were only discovered during surgery, was 6 mm.

A more accurate but invasive test used to differentiate pituitary from ectopic or adrenal Cushing's syndrome is inferior petrosal sinus sampling. A corticotropin gradient sample via BIPSS is required to confirm diagnosis when pituitary MRI imaging and biochemical diagnostic tests have been inconclusive. A basal central:peripheral ratio of over 3:1 when CRH is administered is indicative of Cushing’s disease. This test has been the gold standard for distinguishing between Cushing's disease and ectopic corticotropin syndrome. The BIPSS has a sensitivity and specificity of 94% for Cushing's disease but it is usually used as a last resort due to its invasiveness, rare but serious complications, and the expertise required to perform it.

Another diagnostic test used is the urinary free cortisol (UFC) test, which measures the excess cortisol excreted by the kidneys into the urine. Results of 4x higher cortisol levels than normal are likely to be Cushing's disease. This test should be repeated three times in order to exclude any normally occurring periods of hypercortisolism. The UFC test has a specificity of 81% and thus has a high rate of false-positives that are due to pseudo-Cushing states, sleep apnea, polycystic ovary syndrome, familial glucocorticoid resistance, and hyperthyroidism.

The late-night or midnight salivary cortisol test has been gaining support due to its ease of collection and stability at room temperature, therefore it can be assigned to outpatients. The test measures free circulating cortisol and has both a sensitivity and specificity of 95-98%. This test is especially useful for diagnosing children.

In suspected cases of Addison's disease, demonstration of low adrenal hormone levels even after appropriate stimulation (called the ACTH stimulation test or synacthen test) with synthetic pituitary ACTH hormone tetracosactide is needed for the diagnosis. Two tests are performed, the short and the long test. It should be noted that dexamethasone does not cross-react with the assay and can be administered concomitantly during testing.

The short test compares blood cortisol levels before and after 250 micrograms of tetracosactide (intramuscular or intravenous) is given. If, one hour later, plasma cortisol exceeds 170 nmol/l and has risen by at least 330 nmol/l to at least 690 nmol/l, adrenal failure is excluded. If the short test is abnormal, the long test is used to differentiate between primary adrenal insufficiency and secondary adrenocortical insufficiency.

The long test uses 1 mg tetracosactide (intramuscular). Blood is taken 1, 4, 8, and 24 hr later. Normal plasma cortisol level should reach 1000 nmol/l by 4 hr. In primary Addison's disease, the cortisol level is reduced at all stages, whereas in secondary corticoadrenal insufficiency, a delayed but normal response is seen.

Other tests may be performed to distinguish between various causes of hypoadrenalism, including renin and adrenocorticotropic hormone levels, as well as medical imaging - usually in the form of ultrasound, computed tomography or magnetic resonance imaging.

Adrenoleukodystrophy, and the milder form, adrenomyeloneuropathy, cause adrenal insufficiency combined with neurological symptoms. These diseases are estimated to be the cause of adrenal insufficiency in about 35% of male patients with idiopathic Addison’s disease, and should be considered in the differential diagnosis of any male with adrenal insufficiency. Diagnosis is made by a blood test to detect very long chain fatty acids.

Biopsy is the only means of accurate diagnosis as no autoantigen has been discovered. Biopsy of the pituitary gland is not easily performed with safety as it sits under the brain, however, a test does exist to detect antibodies to the pituitary without biopsy: autoantibodies to M(r) 49,000 pituitary cytosolic protein may represent markers for an immunological process affecting the pituitary gland. Tests for normal pituitary gland hormone production tend to be expensive and in some cases difficult to administer. In addition, certain hormone levels vary largely throughout the day and in response to metabolic factors, making abnormal levels difficult to calibrate—further hampering diagnosis.

During pregnancy, the thyroid gland must produce 50% more thyroid hormone to provide enough thyroid hormone for the developing fetus and the expectant mother. In pregnancy, free thyroxine levels may be lower than anticipated due to increased binding to thyroid binding globulin and decreased binding to albumin. They should either be corrected for the stage of pregnancy, or total thyroxine levels should be used instead for diagnosis. TSH values may also be lower than normal (particularly in the first trimester) and the normal range should be adjusted for the stage of pregnancy.

In pregnancy, subclinical hypothyroidism is defined as a TSH between 2.5 and 10 mIU/l with a normal thyroxine level, while those with TSH above 10 mIU/l are considered to be overtly hypothyroid even if the thyroxine level is normal. Antibodies against TPO may be important in making decisions about treatment, and should, therefore, be determined in women with abnormal thyroid function tests.

Determination of TPO antibodies may be considered as part of the assessment of recurrent miscarriage, as subtle thyroid dysfunction can be associated with pregnancy loss, but this recommendation is not universal, and presence of thyroid antibodies may not predict future outcome.

Hormonal assay : there may be low level of T4, TSH, Estrogen, Gonadotropin, Cortisol and ACTH depending on the extent of necrosis

MRI of the pituitary and hypothalamus: this helps to exclude tumor or other pathologies.

Some people only use Conn's syndrome for when it occurs due to an adrenal adenoma (a type of benign tumor). In practice, however, the terms are often used interchangeably, regardless of the underlying physiology.

An adrenal "incidentaloma" is an adrenal tumor found by coincidence without clinical symptoms or suspicion. It is one of the more common unexpected findings revealed by computed tomography (CT), magnetic resonance imaging (MRI), or ultrasonography.

In these cases, a dexamethasone suppression test is often used to detect cortisol excess, and metanephrines or catecholamines for excess of these hormones. Tumors under 3 cm are generally considered benign and are only treated if there are grounds for a diagnosis of Cushing's syndrome or pheochromocytoma. Radiodensity gives a clue in estimating malignancy risk, wherein a tumor with 10 Hounsfield units or less on an unenhanced CT is probably a lipid-rich adenoma.

Hormonal evaluation includes:

- 1-mg overnight dexamethasone suppression test

- 24-hour urinary specimen for measurement of fractionated metanephrines and catecholamines

- Blood plasma aldosterone concentration and plasma renin activity, "if hypertension is present"

On CT scan, benign adenomas typically are of low radiographic density (due to fat content) and show rapid washout of contrast medium (50% or more of the contrast medium washes out at 10 minutes). If the hormonal evaluation is negative and imaging suggests benign, followup should be considered with imaging at 6, 12, and 24 months and repeat hormonal evaluation yearly for 4 years

Primary hyperaldosteronism can be mimicked by Liddle syndrome, and by ingestion of licorice and other foods containing glycyrrhizin. In one case report, hypertension and quadriparesis resulted from intoxication with a non-alcoholic pastis (an anise-flavored aperitif containing glycyrrhizinic acid).

In the developed world, nearly all cases of congenital hypothyroidism are detected by the newborn screening program. These are based on measurement of TSH or thyroxine (T) on the second or third day of life (Heel prick).

If the TSH is high, or the T low, the infant's doctor and parents are called and a referral to a pediatric endocrinologist is recommended to confirm the diagnosis and initiate treatment. Often a technetium (Tc-99m pertechnetate) thyroid scan is performed to detect a structurally abnormal gland. A radioactive iodine (RAIU) exam will help differentiate congenital absence or a defect in organification (a process necessary to make thyroid hormone).

In a study of 1,034 symptomatic adults, Sheehan syndrome was found to be the sixth most frequent etiology of growth hormone deficiency, being responsible for 3.1% of cases (versus 53.9% due to a pituitary tumor).

Most Cushing's syndrome cases are caused by corticosteroid medications, such as those used for asthma, arthritis, eczema and other inflammatory conditions. Consequently, most patients are effectively treated by carefully tapering off (and eventually stopping) the medication that causes the symptoms.

If an adrenal adenoma is identified, it may be removed by surgery. An ACTH-secreting corticotrophic pituitary adenoma should be removed after diagnosis. Regardless of the adenoma's location, most patients require steroid replacement postoperatively at least in the interim, as long-term suppression of pituitary ACTH and normal adrenal tissue does not recover immediately. Clearly, if both adrenals are removed, replacement with hydrocortisone or prednisolone is imperative.

In those patients not suited for or unwilling to undergo surgery, several drugs have been found to inhibit cortisol synthesis (e.g. ketoconazole, metyrapone) but they are of limited efficacy. Mifepristone is a powerful glucocorticoid type II receptor antagonist and, since it does not interfere with normal cortisol homeostatis type I receptor transmission, may be especially useful for treating the cognitive effects of Cushing's syndrome. However, the medication faces considerable controversy due to its use as an abortifacient. In February 2012, the FDA approved mifepristone to control high blood sugar levels (hyperglycemia) in adult patients who are not candidates for surgery, or who did not respond to prior surgery, with the warning that mifepristone should never be used by pregnant women.

Removal of the adrenals in the absence of a known tumor is occasionally performed to eliminate the production of excess cortisol. In some occasions, this removes negative feedback from a previously occult pituitary adenoma, which starts growing rapidly and produces extreme levels of ACTH, leading to hyperpigmentation. This clinical situation is known as Nelson's syndrome.

Routine laboratory investigations may show:

- Hypercalcemia

- Hypoglycemia, low blood sugar (worse in children due to loss of glucocorticoid's glucogenic effects)

- Hyponatremia (low blood sodium levels), due to loss of production of the hormone aldosterone, to the kidney's inability to excrete free water in the absence of sufficient cortisol, and also the effect of corticotropin-releasing hormone to stimulate secretion of ADH.

- Hyperkalemia (raised blood potassium levels), due to loss of production of the hormone aldosterone.

- Eosinophilia and lymphocytosis (increased number of eosinophils or lymphocytes, two types of white blood cells)

- Metabolic acidosis (increased blood acidity), also is due to loss of the hormone aldosterone because sodium reabsorption in the distal tubule is linked with acid/hydrogen ion (H) secretion. Absent or insufficient levels of aldosterone stimulation of the renal distal tubule leads to sodium wasting in the urine and H retention in the serum.

Like the other forms of CAH, suspicion of severe 3β-HSD CAH is usually raised by the appearance of the genitalia at birth or by development of a salt-wasting crisis in the first month of life. The diagnosis is usually confirmed by the distinctive pattern of adrenal steroids: elevated pregnenolone, 17α-hydroxypregnenolone, DHEA, and renin. In clinical circumstances this form of CAH has sometimes been difficult to distinguish from the more common 21-hydroxylase deficient CAH because of the 17OHP elevation, or from simple premature adrenarche because of the DHEA elevation.

Hypoadrenocorticism is often tentatively diagnosed on the basis of history, physical findings, clinical pathology, and, for primary adrenal insufficiency, characteristic electrolyte abnormalities.

- Clinical pathology - Abnormalities may be identified on hematology, biochemistry and urinalysis. Elevated concentrations of potassium (hyperkalemia), and low sodium and chloride values (hyponatremia and hypochloremia) are the classic electrolyte alterations. The sodium/potassium ratio often is <27 (normal is between 27:1 and 40:1) and maybe <20 in animals with primary adrenal insufficiency. However, not all dogs have an abnormal electrolyte ratio during an Addisonian episode.

- ECG - The severity of the ECG abnormalities correlates with the severity of the hyperkalemia. Therefore the ECG can be used to identify and estimate the severity of hyperkalemia and to monitor changes in serum potassium during therapy.

- Diagnostic imaging - Abdominal ultrasound may reveal small adrenal glands, suggesting adrenocortical atrophy. However, finding normal-sized adrenal glands does not rule out hypoadrenocorticism. Rarely, megaesophagus is evident on radiographs.

- ACTH stimulation test - Confirmation requires evaluation of an ACTH stimulation test. Basline plasma cortisol and urine cortisol/Cr ratios are unreliable for confirming the diagnosis. One major diagnostic criterion is abnormally decreased post-ACTH plasma cortisol. Normal plasma cortisol after ACTH stimulation rules out adrenal insufficiency. The only accurate test for hypoadrenocorticism is an ACTH stimulation test.

The ACTH stimulation test does not distinguish between primary and secondary hypoadrenocorticism, or adrenocortical destruction caused by mitotane overdose. Differentiation between primary and secondary hypoadrenocorticism can be made by periodically measuring serum electrolytes, baseline endogenous ACTH, or possibly serum or plasma aldosterone during the ACTH stimulation test. While most corticosteroid drugs will invalidate the results of an ACTH test, dexamethasone may be used in the event of an Addison's emergency without fear of compromising the results of the test.

In general, hypoadrenocorticism is underdiagnosed in dogs, and one must have a clinical suspicion of it as an underlying disorder for many presenting complaints. Females are overrepresented, and the disease often appears in middle age (four to seven years), although any age or gender may be affected. Dogs with hypoadrenocorticism may also have one of several autoimmune disorders. Because it is an endocrine disorder, they may also suffer from neuropathy and some endocrine-related eye diseases.

The first-line treatment of Cushing's disease is surgical resection of ACTH-secreting pituitary adenoma; this surgery involves removal of the tumor via transsphenoidal surgery (TSS).

There are two possible options for access to sphenoidal sinus including of endonosal approach (through the nostril) or sublabial approach (through an incision under the upper lip); many factors such as the size of nostril, the size of the lesion, and the preferences of the surgeon cause the selection of one access route over the other.

Some tumors do not contain a discrete border between tumor and pituitary gland; therefore, careful sectioning through pituitary gland may be required to identify the location of tumor. The probability of successful resection is higher in patients where the tumor was identified at initial surgery in comparison to patients where no tumor was found initially; the overall remission rates in patients with microadenomas undergoing TSS are in range of 65%-90%, and the remission rate in patients with macroadenomas are lower than 65%. patients with persistent disease after initial surgery are treated with repeated pituitary surgery as soon as the active persistent disease is evident; however, reoperation has lower success rate and increases the risk of pituitary insufficiency.

Pituitary radiation therapy is another option for treatment of postoperative persisting hypercortisolemia following unsuccessful transsphenoidal surgery. External-beam pituitary RT is more effective treatment for pediatric CD in children with cure rates of 80%-88%. Hypopituitarism specifically growth hormone deficiency has been reported as the only most common late morbidity of this treatment; GHD has been reported in 36% and 68% of the patients undergoing post pituitary RT for Cushing's disease.

Bilateral adrenalectomy is another treatment which provides immediate reduction of cortisol level and control of hypercortisolism. However, it requires education of patients, because lifelong glucocorticoid and mineralocorticoid replacement therapy is needed for these patients. One of the major complications of this treatment is progression of Nelson's syndrome which is caused by enhance level of tumor growth and ACTH secretion post adrenalectomy in 8%-29% of patients with CD.

During post surgical recovery, patients collect 24-hour urine sample and blood sample for detecting the level of cortisol with the purpose of cure test; level of cortisol near the detection limit assay, corresponds to cure. Hormonal replacement such as steroid is given to patients because of steroid withdrawal. After the completion of collecting urine and blood samples, patients are asked to switch to glucocorticoid such as prednisone to decrease symptoms associated with adrenal withdrawal.

A study of 3,525 cases of TSS for Cushing's disease in the nationally representative

sample of US hospitals between 1993 and 2002 was conducted and revealed the following results: the in-hospital mortality rate was 0.7%; the complication rate was 42.1%. Diabetes insipidus (15%), fluid and electrolyte abnormalities (12.5%), and neurological deficits (5.6%) were the most common complications reported. The analyses of the study show that complications were more likely in patients with pre-operative comorbidities. Patients older than 64 years were more likely to have an adverse outcome and prolonged hospital stay. Women were 0.3 times less likely to have adverse outcomes in comparison to men.

As with hyperthyroidism, TSH is suppressed. Both free and serum (or total) T3 and T4 are elevated. An elevation in thyroid hormone levels is suggestive of thyroid storm when accompanied by signs of severe hyperthyroidism but is not diagnostic as it may also correlate with uncomplicated hyperthyroidism. Moreover, serum T3 may be normal in critically ill patients due to decreased conversion of T4 to T3. Other potential abnormalities include the following:

- Hyperglycemia likely due to catecholamine-mediated effects on insulin release and metabolism as well as increased glycogenolysis, evolving into hypoglycemia when glycogen stores are depleted

- Elevated aspartate aminotransferase (AST), bilirubin and lactate dehydrogenase (LDH)

- Hypercalcemia and elevated alkaline phosphatase due to increased bone resorption

- Elevated white blood cell count

Most children born with congenital hypothyroidism and correctly treated with thyroxine grow and develop normally in all respects. Even most of those with athyreosis and undetectable T levels at birth develop with normal intelligence, although as a population academic performance tends to be below that of siblings and mild learning problems occur in some.

Congenital hypothyroidism is the most common preventable cause of intellectual disability. Few treatments in the practice of medicine provide as large a benefit for as small an effort.

The developmental quotient (DQ, as per Gesell Developmental Schedules) of children with hypothyroidism at age 24 months that have received treatment within the first 3 weeks of birth is summarised below:

It is recommended that magnetic resonance imaging (MRI) scan of the pituitary gland is performed if the diagnosis is suspected; this has a sensitivity of over 90% for detecting pituitary apoplexy; it may demonstrate infarction (tissue damage due to a decreased blood supply) or hemorrhage. Different MRI sequences can be used to establish when the apoplexy occurred, and the predominant form of damage (hemorrhage or infarction). If MRI is not suitable (e.g. due to claustrophobia or the presence of metal-containing implants), a computed tomography (CT) scan may demonstrate abnormalities in the pituitary gland, although it is less reliable. Many pituitary tumors (25%) are found to have areas of hemorrhagic infarction on MRI scans, but apoplexy is not said to exist unless it is accompanied by symptoms.

In some instances, lumbar puncture may be required if there is a suspicion that the symptoms might be caused by other problems (meningitis or subarachnoid hemorrhage). This is the examination of the cerebrospinal fluid that envelops the brain and the spinal cord; the sample is obtained with a needle that is passed under local anesthetic into the spine. In pituitary apoplexy the results are typically normal, although abnormalities may be detected if blood from the pituitary has entered the subarachnoid space. If there is remaining doubt about the possibility of subarachnoid hemorrhage (SAH), a magnetic resonance angiogram (MRI with a contrast agent) may be required to identify aneurysms of the brain blood vessels, the most common cause of SAH.

Professional guidelines recommend that if pituitary apoplexy is suspected or confirmed, the minimal blood tests performed should include a complete blood count, urea (a measure of renal function, usually performed together with creatinine), electrolytes (sodium and potassium), liver function tests, routine coagulation testing, and a hormonal panel including IGF-1, growth hormone, prolactin, luteinizing hormone, follicle-stimulating hormone, thyroid-stimulating hormone, thyroid hormone, and either testosterone in men or estradiol in women.

Visual field testing is recommended as soon as possible after diagnosis, as it quantifies the severity of any optic nerve involvement, and may be required to decide on surgical treatment.

As with other forms of CAH, the primary therapy of 11β-hydroxylase deficient CAH is lifelong glucocorticoid replacement in sufficient doses to prevent adrenal insufficiency and suppress excess mineralocorticoid and androgen production.

Salt-wasting in infancy responds to intravenous saline, dextrose, and high dose hydrocortisone, but prolonged fludrocortisone replacement is usually not necessary. The hypertension is ameliorated by glucocorticoid suppression of DOC.

Long term glucocorticoid replacement issues are similar to those of 21-hydroxylase CAH, and involve careful balance between doses sufficient to suppress androgens while avoiding suppression of growth. Because the enzyme defect does not affect sex steroid synthesis, gonadal function at puberty and long-term fertility should be normal if adrenal androgen production is controlled. See congenital adrenal hyperplasia for a more detailed discussion of androgen suppression and fertility potential in adolescent and adult women.