Recent studies have shown that primary aldosteronism (PA) is the most common cause of secondary hypertension with a prevalence of approximately 5-10% among all hypertensive patients and an even higher prevalence among selected patients with advanced stages of hypertension and resistant hypertension.
(1) Screening for PA among hypertensive patients is important due to its association with risk for cardiovascular disease and renal damage, (1) and non-invasive salivary aldosterone measurements have recently been explored as a means to facilitate this screening. Morning salivary aldosterone measurements alone were found to have some ability to discriminate between patients with PA and essential hypertension, and the presence or absence of a diurnal decline showed promise for distinguishing between the two forms of the disease (adenomas vs. bilateral hyperplasia). (2) Dysregulation of circulating aldosterone levels has also been associated with psychiatric disorders, and a recent study has similarly reported a significant negative association between morning salivary aldosterone levels and trait anxiety scores. Those with the high anxiety trait may be associated with an inability to respond with adequate cortisol levels during stress. (3) Produced largely in the adrenal glands, aldosterone is classified as a mineralocorticoid steroid since its classical effect is to regulate the transport of sodium and water across cells of the kidney in exchange for potassium and hydrogen ions, thereby regulating blood volume and pressure. (4,5) Additionally, rapid non-genomic actions and local production of aldosterone have been identified in other tissues, including the heart, vascular system, adrenal gland, and kidney. These non-genomic mechanisms are being studied in connection with a range of diseases including cardiovascular disease, cirrhosis, kidney disease, insulin resistance, and diabetes. (6,7,8) No specific binding protein for aldosterone has been identified in blood. (4) Circulating aldosterone not bound to serum proteins enters saliva by passive diffusion. (9) Salivary aldosterone levels correspond approximately to 30% of those found in plasma, with good correlation found between plasma and non-extracted salivary aldosterone. (10) Salivary aldosterone levels are unaffected by salivary flow rate or hormone-binding proteins. (11) Both salivary and plasma aldosterone increase significantly while standing, compared to being seated; this effect is significantly higher in females than in males. A diurnal rhythm for salivary aldosterone exists for healthy individuals, with highest levels in the morning. (10)