Gitelman Syndrome

<p>Overview of common and distinctive features — The tubular defects in sodium chloride transport are almost identical to that seen with chronic ingestion of a loop diuretic (mimicking <a href="brain://AoQzmYyq5FSFK47Sf145Cw/BartterSyndrome" class="thought-link">Bartter Syndrome</a>) or a thiazide diuretic (mimicking <a href="brain://YI5w7m1qnVqcZteV6h9sjw/GitelmanSyndrome" class="thought-link">Gitelman Syndrome</a>).&#160;

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The salt wasting that occurs results in the following features <b><i>common</i></b> to patients with both disorders:</p>

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<li>Impaired sodium chloride reabsorption leads to mild volume depletion and activation of the renin-angiotensin-aldosterone system.</li>

<li>The combination of secondary hyperaldosteronism and increased distal flow and sodium delivery enhances potassium and hydrogen secretion at the secretory sites in the connecting tubules and collecting tubules, leading to hypokalemia and metabolic alkalosis.&#160;</li>

<li>Patients with Bartter and Gitelman syndromes, as well as heterozygotes of both disorders, have a lower blood pressure than seen in the general population [6]. In addition to volume depletion, another possible contributor to a lower blood pressure in Bartter syndrome is increased renal release of vasodilator prostaglandins (prostaglandin E2).&#160;</li>

<li>Diluting capacity is reduced in patients with both disorders because maximal dilution of the urine requires intact function of both the thick ascending limb of the loop of Henle and the distal tubule. In normal individuals, sodium chloride is reabsorbed without water in both sites and, if ADH is suppressed, maximal urine dilution occurs.

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<p>However, there are <b><i>distinctive</i></b> features that correspond to the tubular location of disrupted sodium chloride reabsorption (ie, loop of Henle in Bartter syndrome and distal tubule in Gitelman syndrome) (table 1):</p>

<ul>

<li>Patients with Bartter syndrome tend to have a blunted response to a loop diuretic, while patients with Gitelman syndrome tend to have a blunted response to a thiazide diuretic.</li>

<li>Concentrating ability is impaired in Bartter syndrome but is relatively preserved in Gitelman syndrome [2,10,11]. Maximal urine concentration requires intact function of the thick ascending limb of the loop of Henle and maximal ADH activity, but is not substantially impaired by the reduced distal tubule function in Gitelman syndrome.</li>

<li>Urinary calcium excretion is normal or high in patients with Bartter syndrome, as it is with a loop diuretic, since calcium reabsorption in the thick ascending limb requires normal NaCl reabsorption. In contrast, urinary calcium excretion is typically reduced in patients with Gitelman syndrome as it is with a thiazide diuretic.</li>

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