Clinical usefulness of measuring TTKG (Transtular Potassium Gradient) in patients with hypertension for screening of primary aldosteronism

Program: Late-Breaking Abstracts
Session: SAT-LB-Late-Breaking Poster Session 1
Bench to Bedside
Saturday, June 15, 2013: 1:45 PM-3:45 PM
Expo Halls ABC (Moscone Center)

Poster Board SAT-LB-10
Masataka Kudo, Ryo Morimoto, Yoshitsugu Iwakura, Yoshikiyo Ono, Masahiro Nezu, Ken Matsuda, Sadayoshi Ito and Fumitoshi Satoh*
Tohoku University Hospital
Introduction: TTKG (Transtular Potassium Gradient) is an index of urinary K excretion, and also considered to reflect mainly aldosterone bioactivity. The plasma aldosterone concentration(PAC)/plasma renin activity(PRA) ratio (ARR) is widely used for the screening of primaryaldosteronism (PA).The purpose of this study is to ascertain whether TTKG could be an index of the screening of PA along with ARR.

Method: 440 patients (197 men, women 243, age 53.74±12.12) with hypertension in the Tohoku University hospital from July 2009 to December 2011 were recruited. We unified the antihypertensive medications only to Ca antagonist and  alpha blocker before measuring TTKG.All patients were measured TTKG and performed captopril loading test (CAPT: captopril 50 mg PO). The patients with basal ARR>20 and ARR in CAPT>20 were diagnosed as PA and successively performed adrenal vein sampling (AVS) .

 Results: 284/440 patients were diagnosed as PA and 132/284 patients presented with unilateral excessive aldosterone secretion and were underwent adrenalectomy as aldosterone producing adenoma (APA).In PA patients, 37/284 patients(13%) had hypokalemia(serum potassium < 3.5mEq/l), nevertheless, 168/284 patients(59.2%) had relatively high TTKG( 4.95±0.12).This data indicate that even the PA patients have normal serum potassium level, TTKG may have already increased. Next, we investigated the relationship between PAC and TTKG, PAC and Urine K/ Urine Na, PAC and FEk(%).TTKG showed a correlation to PAC (R= 0.514, p<0.01), significantly compared to Urine K/ Urine Na and FEk.  When we divided all patients into two groups (group A: PAC≥12.0ng/ml, group B: PAC<12.0ng/ml ), TTKG was significantly high level in a group A(6.00±3.10 in group A vs. 4.11±1.60 in group B).When we divided PA patients into two groups (group S: surgical treatment group, group M: medical treatmt group), TTKG was significantly high level in a group S (5.82±3.05 in group S vs. 4.24±1.81 in group M). Multivariate regression analysis revealed that Age, eGFR and TTKG were independent predictors of PAC in all cases. By extension, multivariate logistic analysis revealed that TTKG was independently related to Treatment (whether or not surgical treatment finally chosen after AVS) in PA patients (odds ratio:1.247, 95% confidence interval[1.087-1.431]] for TTKG, p<0.01) , in addition to Age and PAC.

Conclusion: In addition to ARR, measuring TTKG in hypertensive patients may be useful for screening PA. The level of TTKG(>4.0) can predict relatively high level of PAC (>12.0 ng/ml) .

(1)Nishikawa T et al., Endocrine Journal 2007; 54:487-497(2)Sau-Cheung Ti et al., J. Clin. Endocrinol. Metab. 2005 90:72-78(3)Paolo Mulatero et al.,J. Clin. Endocrinol. Metab. 2004 89: 1045-1050,

Nothing to Disclose: MK, RM, YI, YO, MN, KM, SI, FS

*Please take note of The Endocrine Society's News Embargo Policy at http://www.endo-society.org/endo2013/media.cfm

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