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Plasma renin activity and hypertensive organ manifestations in 50-year-old males
Insights
Low sodium excretion in hypertension indicates a more severe condition, not a milder one. This finding suggests low renin hypertension is associated with lower kidney function and higher blood pressure.
Area of Science:
- Cardiology
- Nephrology
- Endocrinology
Background:
- Hypertension is a significant cardiovascular risk factor.
- Understanding subtypes of hypertension, like low renin hypertension, is crucial for effective management.
- Previous research has explored the relationship between renin levels, sodium excretion, and blood pressure, but findings remain debated.
Purpose of the Study:
- To investigate the relationship between plasma renin activity (PRA), urinary sodium excretion, and glomerular filtration rate (GFR) in hypertensive individuals.
- To determine if low sodium excretion is associated with a more severe form of hypertension.
- To compare hypertensive groups with varying renin levels regarding blood pressure and renal function.
Main Methods:
- A subsample of 50-year-old males from Göteborg, Sweden, was selected, including a reference group and a hypertension group.
- Investigations included blood pressure measurement, plasma renin activity (PRA), urinary sodium and norepinephrine excretion, and GFR.
- Hypertensive participants were categorized based on sodium excretion (low, normal, high) and renin levels (low, normal, high).
Main Results:
- No significant difference in PRA or sodium excretion was found between the reference and hypertension groups.
- Low sodium excretion in hypertensives was associated with higher blood pressure, lower GFR, and reversed diurnal urine excretion rhythm.
- Hypertensives with low renin levels exhibited the lowest GFR, while increasing renin levels correlated with increased GFR and decreased resting blood pressure.
Conclusions:
- Low sodium excretion is an indicator of more severe hypertension with increased renal resistance.
- Low renin hypertension is not a milder form but rather a more severe manifestation of the condition.
- These findings highlight the importance of considering sodium excretion and renin levels in classifying hypertension severity and guiding treatment.
Abstract:
From a screening examination in a randomly selected third of the 50-year-old male population in Göteborg, Sweden, a 10% subsample was selected as a reference group (n=80). All untreated persons with SBP greater than 175 or DBP greater than 115 mmHg on two separate occasions made up the hypertension group (n=35). The reference group and the hypertension group were subjected to the same investigations, including BP measurement before and after rest and determination of plasma renin activity (PRA), urinary sodium and norepinephrine excretion and GFR. Plasma renin activity was approximately normally distributed in both the reference and the hypertension group. Mean values were 0.78 +/- 0.18 and 0.65 +/- 0.17 ng/ml/h respectively, the difference being almost statistically significant (0.10 greater than p greater than 0.05). There was no difference with respect to sodium excretion between the reference group and the hypertension group. In the reference group, heart rate was positively correlated to PRA and to urinary norepinephrine excretion during the day. No linear correlation between PAR and BP was found, either in the reference group, or in the hypertension group. Sodium excretion during the day was positively correlated to GFR in the hypertension group, but not in the reference group. Compared to hypertensives with normal or high sodium excretion during the day, the hypertensives with low sodium excretion during the day were characterized by a higher BP, a lower GFR and a reversed diurnal rhythm of urine excretion. Thus, low sodium excretion seemed to indicate more severe hypertension with increased renal resistance during the day. The hypertension group was also divided with regard to sodium excretion into a low, normal and high renin group. The low renin group had the lowest GFR and with rising renin group (from low via normal to high) there was a significant increase in GFR and a significant decrease in resting BP. The results indicate that low renin hypertension is not a more mild, but indeed rather a more severe form of hypertension.