Prevention of EAH focuses on reducing fluid consumption to avoid fluid retention before, during, and after exercise.

EAH is categorized by having a blood serum or plasma sodium level below normal, which is less than 135 mmol/l. Asymptomatic EAH is not normally detected unless the athlete has had a sodium blood serum or plasma test. Hyponatremic encephalopathy may be detect using brain imaging studies and pulmonary edema may be confirmed by x-ray.

The history, physical exam, and laboratory testing are required to determine the underlying cause of hyponatremia. A blood test demonstrating a serum sodium less than 135 mmol/L is diagnostic for hyponatremia. The history and physical exam are necessary to help determine if the patient is hypovolemic, euvolemic, or hypervolemic, which has important implications in determining the underlying cause. An assessment is also made to determine if the patient is experiencing symptoms from their hyponatremia. These include assessments of alertness, concentration, and orientation.

False hyponatremia, also known as spurious, pseudo, hypertonic, or artifactual hyponatremia is when the lab tests read low sodium levels but there is no hypotonicity. In hypertonic hyponatremia, resorption of water by molecules such as glucose (hyperglycemia or diabetes) or mannitol (hypertonic infusion) occurs. In isotonic hyponatremia a measurement error due to high blood triglyceride level (most common) or paraproteinemia occurs. It occurs when using techniques that measure the amount of sodium in a specified volume of serum/plasma, or that dilute the sample before analysis.

Diagnosis is based on clinical and laboratory findings of low serum osmolality and low serum sodium.

Urinalysis reveals a highly concentrated urine with a high fractional excretion of sodium (high sodium urine content compared to the serum sodium).

A suspected diagnosis is based on a serum sodium under 138. A confirmed diagnosis has seven elements: 1) a decreased effective serum osmolality - <275 mOsm/kg of water; 2) urinary sodium concentration high - over 40 mEq/L with adequate dietary salt intake; 3) no recent diuretic usage; 4) no signs of ECF volume depletion or excess; 5) no signs of decreased arterial blood volume - cirrhosis, nehprosis, or congestive heart failure; 6) normal adrenal and thyroid function; and 7) no evidence of hyperglycemia (diabetes mellitus), hypertriglyceridemia, or hyperproteinia (myeloma).

There are nine supplemental features: 1) a low BUN; 2) a low uric acid; 3) a normal creatinine; 4) failure to correct hyponatremia with IV normal saline; 5) successful correction of hyponatremia with fluid restriction; 6) a fractional sodium excretion >1%; 7) a fractional urea excretion >55%; 8) an abnormal water load test; and 9) an elevated plasma AVP.

Antidiuretic hormone (ADH) is released from the posterior pituitary for a number of physiologic reasons. The majority of people with hyponatremia, other than those with excessive water intake (polydipsia) or renal salt wasting, will have elevated ADH as the cause of their hyponatremia. However, not every person with hyponatremia and elevated ADH has SIADH. One approach to a diagnosis is to divide ADH release into appropriate (not SIADH) or inappropriate (SIADH).

Appropriate ADH release can be a result of hypovolemia, a so-called osmotic trigger of ADH release. This may be true hypovolemia, as a result of dehydration with fluid losses replaced by free water. It can also be perceived hypovolemia, as in the conditions of congestive heart failure (CHF) and cirrhosis in which the kidneys perceive a lack of intravascular volume. The hyponatremia caused by appropriate ADH release (from the kidneys' perspective) in both CHF and cirrhosis have been shown to be an independent poor prognostic indicator of mortality.

Appropriate ADH release can also be a result of non-osmotic triggers. Symptoms such as nausea/vomiting and pain are significant causes of ADH release. The combination of osmotic and non-osmotic triggers of ADH release can adequately explain the hyponatremia in the majority of people who are hospitalized with acute illness and are found to have mild to moderate hyponatremia. SIADH is less common than appropriate release of ADH. While it should be considered in a differential, other causes should be considered as well.

Cerebral salt wasting syndrome (CSWS) also presents with hyponatremia, there are signs of dehydration for which reason the management is diametrically opposed to SIADH. Importantly CSWS can be associated with subarachnoid hemorrhage (SAH) which may require fluid supplementation rather than restriction to prevent brain damage.

Most cases of hyponatremia in children are caused by appropriate secretion of antidiuretic hormone rather than SIADH or another cause.

As with all cases of hyponatremia, extreme caution must be taken to avoid the fatal consequences of rapidly correcting electrolytes (e.g. Central pontine myelinolysis, edema). Special considerations with the treatment of potomania are needed. Because this could be a chronic condition, low sodium may be normal for the patient, so an especially careful correction is warranted. It is also very important to note that due to the normal kidney function, and lack of other intrinsic or toxic cause of the electrolyte disturbance, restoration of dietary solutes will correct the electrolytes to normal serum levels. This again must be done with caution.

While CSWS usually appears within the first week after brain injury and spontaneously resolves in 2–4 weeks, it can sometimes last for months or years. In contrast to the use of fluid restriction to treat SIADH, CSWS is treated by replacing the urinary losses of water and sodium with hydration and sodium replacement. The mineralocorticoid medication fludrocortisone can also improve the low sodium level.

Various investigations aid the diagnosis.

- ACTH (cosyntropin) stimulation test

- Cortisol level (to assess the level of glucocorticoids)

- Fasting blood sugar

- Serum potassium (to assess the level of mineralocorticoids)

- Serum sodium

Adrenal crisis is triggered by physiological stress (such as trauma). Activities that have an elevated risk of trauma are best avoided. Treatment must be given within two hours of trauma and consequently it is advisable to carry injectable hydrocortisone in remote areas.

It can be diagnosed clinically in the appropriate context, but may be difficult to confirm radiologically using conventional imaging techniques. Changes are more prominent on MRI than on CT, but often take days or weeks after acute symptom onset to develop. Imaging by MRI typically demonstrates areas of hyperintensity on T2-weighted images.

Excessive sodium and fluid intake:

- IV therapy containing sodium

- As a Transfusion reaction to a rapid blood transfusion.

- High intake of sodium

Sodium and water retention:

- Heart failure

- Liver cirrhosis

- Nephrotic syndrome

- Corticosteroid therapy

- Hyperaldosteronism

- Low protein intake

Fluid shift into the intravascular space:

- Fluid remobilization after burn treatment

- Administration of hypertonic fluids, e.g. mannitol or hypertonic saline solution

- Administration of plasma proteins, such as albumin

CSWS is usually caused by brain injury/trauma or cerebral lesion, tumor, or hematoma. CSWS is a diagnosis of exclusion and may be difficult to distinguish from the syndrome of inappropriate antidiuretic hormone (SIADH), which develops under similar circumstances and also presents with hyponatremia. The main clinical difference is that of total fluid status of the patient: CSWS leads to a relative or overt low blood volume whereas SIADH is consistent with a normal or high blood volume. If blood-sodium levels increase when fluids are restricted, SIADH is more likely.

Dogs with infected with the whipworm "Trichuris trichiura" can exhibit low sodium and high potassium values, as is seen in hypoadrenocorticism; however, their ACTH values are normal.

If deterioration of the adrenal glands progresses far enough, a dog may experience an Addisonian crisis, an acute episode during which potassium levels increase (hyperkalemia), disrupting normal functions of the heart. Arrhythmia can result and blood pressure may drop to dangerously low levels, while the dog's kidneys may cease to function properly. Some 35% of canine Addison's cases are diagnosed as the result of an Addisonian crisis. It is a medical emergency.

Congestive heart failure is the most common result of fluid overload. Also, it may be associated with hyponatremia (hypervolemic hyponatremia).

The normal human kidney, through suppression of anti-diuretic hormone, is normally able to excrete vast amounts of dilute urine. Thus a normal adult can drink up to 20 liters per day of water without becoming hyponatremic. However, the intake of solutes is also necessary to excrete free water. Under normal circumstances, this is clinically irrelevant. In the lack of proper solute intake, the amount of free water excretion can be severely limited. Without adequate solute intake, the normal functioning electrolyte gradient that pulls water into urine will be effectively destroyed.

Briefly, to excrete free water from urine, the urine flow (which is solute clearance + free water clearance) will equal the rate of solute excretion divided by the urine osmolality. With a diet of only solute poor beer, only about 200-300 mOSM (normal 750 mOSM to greater than 900 mOSM) of solute will be excreted per day, capping the amount of free water excretion at four liters. Any intake above 4 liters would lead to a dilution of the serum sodium concentration and thus hyponatremia.

Any vomiting or GI absorptive problems due to alcohol intoxication can also compound the effect of potomania due to additional electrolyte and acid-base disturbances.

There is some laboratory tests that may aid in diagnosis of GSD-V. A muscle biopsy will note the absence of myophosphorylase in muscle fibers. In some cases, acid-Schiff stained glycogen can be seen with microscopy.

Genetic sequencing of the PYGM gene (which codes for the muscle isoform of glycogen phosphorylase) may be done to determine the presence of gene mutations, determining if McArdle's is present. This type of testing is considerably less invasive than a muscle biopsy.

The physician can also perform an ischemic forearm exercise test as described above. Some findings suggest a nonischemic test could be performed with similar results. The nonischemic version of this test would involve not cutting off the blood flow to the exercising arm. Findings consistent with McArdle’s disease would include a failure of lactate in venous blood and exaggerated ammonia levels. These findings would indicate a severe muscle glycolytic block. Ammonia arises from the impaired buffering of ADP, which leads to an increase in AMP concentration resulting in an increase in AMP deamination.

Physicians may also check resting levels of creatine kinase, which are moderately increased in 90% of patients. In some, the level is increased by multitudes - a person without GSD-V will have a CK between 60 and 400IU/L, while a person with the syndrome may have a level of 5,000 IU/L at rest, and may increase to 35,000 IU/L or more with muscle exertion. This can help distinguish McArdle's syndrome from carnitine palmitoyltransferase II deficiency (CPT-II), a lipid-based metabolic disorder which prevents fatty acids from being transported into mitochondria for use as an energy source. Also, serum electrolytes and endocrine studies (such as thyroid function, parathyroid function and growth hormone levels) will also be completed. Urine studies are required only if rhabdomyolysis is suspected. Urine volume, urine sediment and myoglobin levels would be ascertained. If rhabdomyolysis is suspected, serum myoglobin, creatine kinase, lactate dehydrogenase, electrolytes and renal function will be checked.

To minimise the risk of this condition developing from its most common cause, overly rapid reversal of hyponatremia, the hyponatremia should be corrected at a rate not exceeding 10 mmol/L/24 h or 0.5 mEq/L/h; or 18 m/Eq/L/48hrs; thus avoiding demyelination. No large clinical trials have been performed to examine the efficacy of therapeutic re-lowering of serum sodium, or other interventions sometimes advocated such as steroids or plasma exchange.

Alcoholic patients should receive vitamin supplementation and a formal evaluation of their nutritional status.

Once osmotic demyelination has begun, there is no cure or specific treatment. Care is mainly supportive. Alcoholics are usually given vitamins to correct for other deficiencies. The favourable factors contributing to the good outcome in CPM without hyponatremia were: concurrent treatment of all electrolyte disturbances, early Intensive Care Unit involvement at the advent of respiratory complications, early introduction of feeding including thiamine supplements with close monitoring of the electrolyte changes and input.

Research has led to improved outcomes. Animal studies suggest that inositol reduces the severity of osmotic demyelination syndrome if given before attempting to correct chronic hyponatraemia. Further study is required before using inositol in humans for this purpose.

However, diagnosis can be difficult due to the comprehensive measurements used in research that are not always practical in healthcare settings. Hand grip strength alone has also been advocated as a clinical marker of sarcopenia that is simple and cost effective and has good predictive power, although it does not provide comprehensive information.

Exercise remains the intervention of choice for sarcopenia but translation of findings into clinical practice is challenging. The type, duration and intensity of exercise are variable between studies, so an ‘off the shelf’ exercise prescription for sarcopenia remains an aspiration.

The role of nutrition in preventing and treating sarcopenia is less clear. Large, well-designed studies of nutrition particularly in combination with exercise are needed, ideally across healthcare settings. For now, basing nutritional guidance on the evidence available from the wider health context is probably the best approach with little contention in the goals of replacing vitamin D where deficient, and ensuring an adequate intake of calories and protein, although there is debate about whether currently recommended protein intake levels are optimal.

A common pathological cause for a high BMR is fever, since a rise in body temperature increases the rate of cellular metabolic reactions. It is estimated that for every degree Fahrenheit of rise in body temperature, the BMR increases by 7 percent.

Thyroid disease also has a marked effect on BMR, since thyroid hormones regulate the rate of cellular metabolism. Hyperthyroidism—in which there is an increase in the production of thyroid hormones—leads to a high BMR, while hypothyroidism—in which thyroid hormones are depleted—causes a low BMR.

Prolonged periods of abnormal nutrition cause an adaptive change in BMR; this helps the body to maintain a stable body weight in response to the change in food supply. In prolonged malnutrition, the BMR declines, while in prolonged overnutrition, the BMR is increased. Cancer sometimes causes an increase in BMR, perhaps because the cancer cells that form tumors have a high level of metabolic activity.

An abnormal basal metabolic rate is not necessarily indicative of disease; a number of physiological factors can alter the BMR by influencing cellular metabolic activity. For instance, males are more likely than females to have a high BMR, and in women, the BMR may rise to abnormal levels during pregnancy or lactation. An individual's BMR varies greatly with age: infants and children typically have a high BMR, required for growth, while the elderly have a low BMR. Tall, thin people have a higher BMR than their shorter counterparts, even with the same weight, due to the greater surface area of their skin. The metabolic rate also decreases during sleep and increases in exercise, and individuals who exercise regularly have a higher BMR than those who are sedentary. Environmental temperature also has an effect: the BMR is increased in both heat and cold.

Supervised exercise programs have been shown in small studies to improve exercise capacity by several measures.

Oral sucrose treatment (for example a sports drink with 75 grams of sucrose in 660 ml.) taken 30 minutes prior to exercise has been shown to help improve exercise tolerance including a lower heart rate and lower perceived level of exertion compared with placebo.

A working definition for diagnosis was proposed in 1998 by Baumgartner "et al" which uses a measure of lean body mass as determined by dual energy X-ray absorptiometry (DEXA) compared to a normal reference population. His working definition uses a cut point of 2 standard deviations below the mean of lean mass for gender specific healthy young adults.

Since Baumgartner's working definition first appeared, some consensus groups have refined the definition, including the European Working Group on Sarcopenia in Older People (EWGSOP). Their consensus definition is:

- Low muscle mass, (e.g. >2 standard deviations below that mean measured in young adults [aged 18–39 years in the 3rd NHANES population] of the same sex and ethnic background).

And either:

- Low gait speed (e.g. a walking speed below 0.8 m/s in the 4-m walking test)

Or:

- Low muscular strength (e.g. grip strength: <30 kg in males, <20 kg in females)

Severe sarcopenia requires the presence of all three conditions.

A genetic test is available for Type 1 PSSM. This test requires a blood or hair sample, and is less-invasive than muscle biopsy. However, it may be less useful for breeds that are more commonly affected by Type 2 PSSM, such as light horse breeds. Often a muscle biopsy is recommended for horses displaying clinical signs of PSSM but who have negative results for GYS1 mutation.

A muscle biopsy may be taken from the semimembranosis or semitendinosis (hamstring) muscles. The biopsy is stained for glycogen, and the intensity of stain uptake in the muscle, as well as the presence of any inclusions, helps to determine the diagnosis of PSSM. This test is the only method for diagnosing Type 2 PSSM. Horses with Type 1 PSSM will usually have between 1.5-2 times the normal levels of glycogen in their skeletal muscle. While abnormalities indicating muscle damage can be seen on histologic sections of muscle as young as 1 month of age, abnormal polysaccharide accumulation may take up to 3 years to develop.