Introduction

Definition of Gitelman Syndrome

Gitelman syndrome (GS) is a hereditary condition in which  the kidneys excrete too much potassium, leading to low potassium levels in the blood, causing metabolic alkalosis, low calcium levels in urine, low magnesium levels, and high  renin and aldosterone levels. Gitelman syndrome is also referred as  familial hypokalemia-hypomagnesemia.¹

Overview of the condition

It is estimated that the prevalence is around 1 in 40,000 people, leading to a heterozygote prevalence of about 1% in Caucasian populations, making it a common inherited renal tubular disorder.² The condition is the result of mutations that inactivate both copies of the gene.³ Both low magnesium levels and reduced calcium levels in the urine strongly indicate the presence of GS; however, low magnesium levels may not always be present, and calcium levels in the urine can vary greatly. Based on clinical and biological characteristics, sometimes it can be challenging to differentiate GS from other salt-losing nephropathies. Genetic testing is becoming more accessible for genetic screening, although it still comes with a high cost. Cruz and colleagues claimed that GS leads to a greatly decreased quality of life, comparable to individuals with congestive heart failure or diabetes.¹

Importance of Effective Management and Treatment

The management of Gitelman syndrome focuses on addressing the particular symptoms seen in each person. Genetic counseling may be helpful for Affected individuals and their families. Due to its rarity, even experienced private practice or academic nephrologists may lack experience in diagnosing or treating this disease.⁴

Effective management and treatment of GS is crucial  because it causes electrolyte and fluid imbalance of the kidneys. The strategies include:

• Balancing electrolytes and fluid
• Preventing complications
• Preventing long-term damage
• Improving quality of life
• Monitoring and adjustments

Diagnosis

Clinical Presentation and Symptoms

Gitelman syndrome is a condition affecting the kidneys that leads to a disruption in the levels of charged particles (ions) in the body, such as potassium, magnesium, and calcium ions.

The indications and manifestations of Gitelman syndrome typically begin to show in the later stages of childhood or during adolescence. Typical characteristics of this condition consists of uncomfortable muscle contractions (tetany), muscle fatigue or spasms, lightheadedness, and a desire for salt. Paresthesias, a tingling or prickly feeling on the skin, is frequently experienced, especially on the face. Some people with Gitelman syndrome may suffer from extreme tiredness, low blood pressure, and a painful joint condition known as chondrocalcinosis. Research indicates that Gitelman syndrome could raise the chance of developing a hazardous heart rhythm issue known as ventricular arrhythmia.⁵

Diagnostic Criteria

A diagnosis of Gitelman syndrome relies on conducting a comprehensive clinical evaluation, performing various specialized tests, recognizing characteristic symptoms, and taking a detailed patient history. After observing other common causes of hypokalemia and metabolic alkalosis, a diagnosis can be considered.⁴

Laboratory tests⁴

1. Blood tests

Determine serum electrolyte levels, specifically low serum concentrations of magnesium and potassium and/or elevated serum concentrations of renin, and aldosterone.

2. Urine electrolyte measurement

Identify the existence of excessively elevated urinary potassium levels while experiencing low potassium levels. A low urine chloride level typically indicates gastrointestinal losses from vomiting or diarrhea. A diagnosis of Gitelman syndrome can be likened to having low urinary calcium levels.

Genetic testing⁴

Genetic testing is able to identify mutations in the exact genes responsible for the disorder, but is solely offered as a diagnostic option at specialized labs. In most cases, genetic testing is unnecessary for diagnosing a condition.

Goals of Treatment

The treatment goals for GS can be:

• Symptom relief
• Prevention of complications
• Electrolyte and fluid balance
• Improvement of QOL
• Prevention of long-term damage
• Monitoring and adjustments (if necessary)

The treatment options for GS includes both pharmacological and non-pharmacological treatment.

Pharmacological Treatment

Electrolyte replacement therapy

The initial treatment still involves long-term replacement of potassium, magnesium, and sodium. It is advised to replenish electrolytes through diet while also undergoing extended potassium and magnesium therapy. Although receiving the expert guidance on treatment, addressing electrolyte imbalances can still prove challenging and may require trying several potassium and magnesium replacement therapies.

The needs for potassium and magnesium therapy vary, and doses should be customized for each person and may be quite high without completely returning serum biochemistry to normal levels. This tablet load can be cumbersome for patients. Furthermore, high doses of oral magnesium treatment result in osmotic diarrhoea, which reduces tolerability. The presence of extra sugar and calories in many high-sodium or high-potassium foods can complicate the substitution of electrolytes in the diet.⁶

While occasional intravenous treatment can provide relief from symptoms, its effectiveness is usually temporary and is often constrained by patient’ willingness and the challenges of obtaining intravenous access. Patients need to be informed that if they experience a diarrhoeal or vomiting illness, they will require more electrolytes and should seek immediate medical attention if symptoms are severe. A decrease in serum potassium by 1 mmol/L indicates a loss of approximately 100-200 mmol of potassium from the body's reserves, and serum potassium levels under 2 mmol/L might require intravenous replenishment treatment. Additional potassium and magnesium therapy is necessary throughout the pregnancy.⁷

Potassium supplements

KCl is the favored choice for salt supplementation as it replenishes the deficiency of potassium and chloride (both of which are impacted).⁸

• Potassium chloride tablet - 600 mg per tablet (8 mmol potassium)
• Potassium chloride syrup - 75 mg per mL (1 mmol per mL)
• Potassium chloride and potassium bicarbonate effervescent tablet - 600 mg potassium chloride and 400 mg potassium bicarbonate

Magnesium supplements

Magnesium supplementation is crucial in patients with hypomagnesemia to prevent chondrocalcinosis.⁹ Restoring magnesium levels is difficult and the bioavailability varies depending on the chelator for Mg2+, leading to adverse effects like diarrhea that persist. It is essential to carefully support the diet that patients follow within salt supplementation.¹⁰

• Magnesium lactate
• Magnesium oxide capsule or tablet
• Magnesium gluconate tablet
• Magnesium glycerophosphate chewable tablet

Diuretics

Potassium-sparing diuretics are a group of diuretics that do not have a potent diuretic impact. Nonetheless, their main purpose is to counteract hypokalemia induced by diuretics such as furosemide and thiazide. They work in the far end of the nephron and are traditionally categorized as either aldosterone inhibitors or blockers of Na+ channels. Due to their ability to suppress aldosterone and contribute to secondary hyperkalemia, these drugs show potential as effective pharmacological agents in Gitelman syndrome. Nonetheless, if the far end of the region is obstructed, will be unable to be reabsorbed some Na+ and water can take place resulting in exacerbated salt depletion. Hence, the patient may be in danger of developing life-threatening hypovolemia.¹¹

Potassium-sparing diuretics like amiloride and eplerenone were included in the same RCT and have shown effectiveness in treating hypokalaemia, reversing metabolic alkalosis, and addressing hypomagnesaemia. However, careful patient selection and monitoring are necessary as their use can potentially worsen hypovolaemia and lead to increased sodium excretion.¹²

Basically, sparing diuretics are utilized in clinical practice only if other treatment choices, like NSAIDs or additional medications, do not result in improvement in phenotype.¹³ In addition, individuals with a severe presentation do not show any improvement with these therapies and the possibility of hypovolemia needs to be thoroughly evaluated.¹¹

Other medications

Treatment with angiotensin-converting-enzyme inhibitors may also contribute to higher levels of serum potassium; however, case studies conducted on patients with Gitelman Syndrome indicate that the dose is frequently restricted due to hypotension or renal dysfunction. At the moment, there are no choices available for directly targeting the genetic mutation at its root.

In the sole randomized controlled trial (RCT) of therapy for Gitelman syndrome, the positive effect of NSAIDs on correcting hypokalemia was counterbalanced by negative side effects like decreased glomerular filtration rate and gastrointestinal issues. NSAIDs should only be taken if the patient is experiencing joint pains.¹²

The goal of growth hormone (GH) is to avoid growth abnormalities. GH is only considered after NSAID treatment fails for the same purpose. Growth hormone is seen as helpful in cases of GS, despite growth retardation being less common.¹⁴ Maybe GH has a greater positive impact on GS because of the inferior phenotype in BS  about growth delay. Fujimura's research¹⁵ found that GH treatment was not effective for every patient. The treatment may have to last longer in order to show effectiveness in adolescents or young adults.¹¹

Non-pharmacological Treatment

Dietary recommendations

It is advised to replenish electrolytes through diet while also undergoing extended potassium and magnesium therapy.¹²

A recent agreement on GS indicated that an appropriate goal for potassium levels could be 3.0 mmol/L. Having potassium-rich foods regularly can help boost potassium levels in your diet.¹⁶ The primary way in which many foods lose potassium is when they are boiled in water. Nonetheless, when the water used for cooking is ingested, all the potassium is also consumed. Steaming vegetables instead of boiling them can help retain potassium, which is not removed in the cooking water.¹⁷

Example of dietary sources of potassium-rich foods:¹²

• Salmon
• Lentils
• V8 juice
• Orange juice
• Fresh fruit and vegetables, such as bananas, spinach, oranges and mushrooms
• Milk
• Coconut water
• Tomato juice

Magnesium can be found in both plant-based and animal-based foods. The magnesium content is decreased through food processing, specifically refining grains, so it is better to choose whole grains.¹⁸

Example of dietary sources of magnesium-rich foods:¹²

• Pumpkin seeds
• Raw almonds
• Spinach
• Brown rice
• Dark chocolate
• Cashew nuts

Sodium and chloride intake adjustments

To compensate for sodium and chloride losses, it is recommended to follow a salt-free diet and supplement with sodium chloride tablets. Extended-release sodium tablets can be taken in four separate doses, with a daily dose ranging from 2.4 to 4.8 g.¹² Salt cravings in many patients can be used to encourage the consumption of salty foods or salt supplements.

There are currently no clinical trials evaluating the benefits of sodium replacement therapy in patients with GS. It seems logical that a higher salt intake would increase renal tubular sodium content, thereby inhibiting the RAAS, reducing alkalosis, and increasing plasma potassium and chloride.¹⁶

Lifestyle modifications

Individuals diagnosed with GS should avoid drinking too much alcohol. Indeed, the improper use of alcohol can result in disruptions in electrolyte levels like hypomagnesemia and hypokalemia.¹⁹ The main reason for these abnormalities is mostly linked to dysfunction in the tubules.²⁰ Both chronic alcoholism and occasional heavy drinking can result in fluctuations in electrolyte levels. Patients with GS who misuse alcohol may suffer from persistently low levels of potassium and episodes of muscle weakness.

Specific beverages such as fruit juice, citrate, bicarbonate-rich drinks, and almond-based drinks can cause metabolic alkalosis and lower blood potassium levels. Fruit juices with organic acids like citrate and malate can cause alkalosis. These organic acids are produced in the Krebs cycle and are mostly oxidized post-absorption.²¹ Moreover, citrate is primarily converted into bicarbonate in the liver, elevating  metabolic alkalosis.

Bicarbonate and high-bicarbonate beverages, such as carbonated waters, can cause a strong alkalizing effect.²² Replacing cow's milk or baby formula with almond-based drinks in children may cause alkalosis and hypokalemia because they have low levels of chloride.²³

Summary

The effective management and treatment of Gitelman syndrome are vital for preventing complications, improving QOL, and ensuring long-term health. Regular monitoring and a personalized approach to treatment help manage the condition effectively and mitigate potential risks associated with electrolyte imbalances. Dietary strategies for managing blood sugar and glucose levels can involve consuming foods high in sodium, potassium, and magnesium or taking supplements with these minerals. Certain foods and drinks can lower plasma potassium and magnesium levels, so patients or parents of children with these syndromes should be aware of them and limit their consumption.