How does a high salt diet lead to changes in cortisol release

Hypertension is a major cause of both mortality and morbidity in the UK. Over secretion of the hormone aldosterone is implicated in around 30% of cases of hypertension seen in secondary health care. At present very few of these patients with hyperaldosteronism are diagnosed as the protocols for diagnosis are complex and invasive. In a recent study, we developed a technique for the continuous monitoring of aldosterone using a novel device called U-Rhythm and found that this was able to differentiate abnormal aldosterone secretion in many cases. To improve our diagnostic efficacy, we need to show whether changing the dietary input of salt can inhibit aldosterone secretion in normal subjects but not in people with hyperaldosteronism. We first need to do a pilot study to see how changes in salt intake alter the 24-hour regulation of aldosterone in normal subjects.The aim of our study is to assess whether high or low salt diet affects aldosterone levels for a healthy individual over a 24-hour period. Our proposed project would involve recruiting 12 healthy volunteers and asking them to adhere to a high or low salt diet for 7 days before using the U-Rhythm technique to monitor aldosterone (and additional hormones) for 24 hours. We will also collect a 24-hour urine sample to measure sodium and aldosterone levels, and blood tests for renin and aldosterone (lying and standing) and renal function (including electrolytes). Additionally, we will ask the participants to exercise on a static bike as aldosterone has been shown to rise in response to this. After a washout period the process will be repeated following 7 days adhering to the alternate diet. All dietary regimens have been prepared by NHS dietitians and will be balanced in all other nutritional components.