Clinical characteristics and outcome of end stage hypertrophic cardiomyopathy: Role of age and heart failure phenotypes

BACKGROUND

A minority of patients with hypertrophic cardiomyopathy (HCM) presents advanced heart failure (HF) during their clinical course, in the context of left ventricular (LV) remodeling with reduced LV ejection fraction (LVEF), or of severe diastolic dysfunction without impaired LVEF. Aim of this study was to describe a multicentric end stage (ES) HCM population and analyze clinical course and outcome among its different phenotypes.

METHODS

Data of all HCM patients from 7 Italian referral centres were retrospectively evaluated. ES was diagnosed in presence of: LVEF <50% (ES-rEF) or NYHA functional class ≥II with severe diastolic dysfunction (ES-pEF). Outcomes were: HCM-related and all-cause mortality; combined arrhythmic events; advanced HF treatments.

RESULTS

Study population included 331 ES patients; 87% presented ES-rEF and 13% ES-pEF. At ES recognition, patients with ES-pEF were more commonly females, had more frequently NYHA III/IV, atrial fibrillation and greater maximal LV wall thickness. Over a median follow-up of 5.6 years, 83 (25%) patients died, 46 (15%) experienced arrhythmic events and (26%) 85 received advanced HF treatments. Incidence of HCM-related and all-cause mortality, and of combined arrhythmic events did not differ in ES-pEF and ES-rEF patients, but ES-pEF patients were less likely to receive advanced HF treatments. Older age at ES recognition was an independent predictor of increased HCM-related mortality (p = 0.01) and reduced access to advanced HF treatments (p < 0.0001).

CONCLUSIONS

Two different HCM-ES phenotypes can be recognized, with ES-pEF showing distinctive features at ES recognition and receiving less frequently advanced HF treatments. Older age at ES recognition has a major impact on outcomes.

Real-world candidacy to mavacamten in a contemporary hypertrophic obstructive cardiomyopathy population

AIMS

In the EXPLORER-HCM trial, mavacamten reduced left ventricular outflow tract obstruction (LVOTO) and improved functional capacity of symptomatic hypertrophic obstructive cardiomyopathy (HOCM) patients. We sought to define the potential use of mavacamten by comparing real-world HOCM patients with those enrolled in EXPLORER-HCM and assessing their eligibility to treatment.

METHODS AND RESULTS

We collected information on HOCM patients followed up at 25 Italian HCM outpatient clinics and with significant LVOTO (i.e. gradient ≥30 mmHg at rest or ≥50 mmHg after Valsalva manoeuvre or exercise) despite pharmacological or non-pharmacological therapy. Pharmacological or non-pharmacological therapy resolved LVOTO in 1044 (61.2%) of the 1706 HOCM patients under active follow-up, whereas 662 patients (38.8%) had persistent LVOTO. Compared to the EXPLORER-HCM trial population, these real-world HOCM patients were older (62.1 ± 14.3 vs. 58.5 ± 12.2 years, p = 0.02), had a lower body mass index (26.8 ± 5.3 vs. 29.7 ± 4.9 kg/m2 , p < 0.0001) and a more frequent history of atrial fibrillation (21.5% vs. 9.8%, p = 0.027). At echocardiography, they had lower left ventricular ejection fraction (LVEF, 66 ± 7% vs. 74 ± 6%, p < 0.0001), higher left ventricular outflow tract gradients at rest (60 ± 27 vs. 52 ± 29 mmHg, p = 0.003), and larger left atrial volume index (49 ± 16 vs. 40 ± 12 ml/m2 , p < 0.0001). Overall, 324 (48.9%) would have been eligible for enrolment in the EXPLORER-HCM trial and 339 (51.2%) for treatment with mavacamten according to European guidelines.

CONCLUSIONS

Real-world HOCM patients differ from the EXPLORER-HCM population for their older age, lower LVEF and larger atrial volume, potentially reflecting a more advanced stage of the disease. About half of real-world HOCM patients were found eligible to mavacamten.

Exploring the Prognostic Performance of MECKI Score in Heart Failure Patients with Non-Valvular Atrial Fibrillation Treated with Edoxaban

INTRODUCTION

Risk stratification in heart failure (HF) is essential for clinical and therapeutic management. The Metabolic Exercise test data combined with Cardiac and Kidney Indexes (MECKI) score is a validated prognostic model for assessing cardiovascular risk in HF patients with reduced ejection fraction (HFrEF). From the validation of the score, the prevalence of HF patients treated with direct oral anticoagulants (DOACs), such as edoxaban, for non-valvular atrial fibrillation (NVAF) has been increasing in recent years. This study aims to evaluate the reliability of the MECKI score in HFrEF patients treated with edoxaban for NVAF.

MATERIALS AND METHODS

This study included consecutive outpatients with HF and NVAF treated with edoxaban (n = 83) who underwent a cardiopulmonary exercise test (CPET). They were matched by propensity score with a retrospective group of HFrEF patients with NVAF treated with vitamin K antagonists (VKAs) from the MECKI score registry (n = 844). The study endpoint was the risk of cardiovascular mortality, urgent heart transplantation, or Left Ventricle Assist Device (LVAD) implantation.

RESULTS

Edoxaban patients were treated with a more optimized HF therapy and had different clinical characteristics, with a similar MECKI score. After propensity score, 77 patients treated with edoxaban were successfully matched with the MECKI-VKA control cohort. In both groups, MECKI accurately predicted the composite endpoint with similar area under the curves (AUC = 0.757 vs. 0.829 in the MECKI-VKA vs. edoxaban-treated group, respectively, p = 0.452). The two populations' survival appeared non-significantly different at the 2-year follow-up.

CONCLUSIONS

this study confirms the prognostic accuracy of the MECKI score in HFrEF patients with NVAF treated with edoxaban, showing improved predictive power compared to VKA-treated patients.

Heart failure patients with improved ejection fraction: Insights from the MECKI score database

AIMS

Improvement of left ventricular ejection fraction is a major goal of heart failure (HF) treatment. However, data on clinical characteristics, exercise performance and prognosis in HF patients who improved ejection fraction (HFimpEF) are scarce. The study aimed to determine whether HFimpEF patients have a distinct clinical phenotype, biology and prognosis than HF patients with persistently reduced ejection fraction (pHFrEF).

METHODS AND RESULTS

A total of 7948 patients enrolled in the Metabolic Exercise Cardiac Kidney Indexes (MECKI) score database were evaluated (median follow-up of 1490 days). We analysed clinical, laboratory, electrocardiographic, echocardiographic, exercise, and survival data from HFimpEF (n = 1504) and pHFrEF (n = 6017) patients. The primary endpoint of the study was the composite of cardiovascular death, left ventricular assist device implantation, and urgent heart transplantation. HFimpEF patients had lower HF severity: left ventricular ejection fraction 44.0 [41.0-47.0] versus 29.7 [24.1-34.5]%, B-type natriuretic peptide 122 [65-296] versus 373 [152-888] pg/ml, haemoglobin 13.5 [12.2-14.6] versus 13.7 [12.5-14.7] g/dl, renal function by the Modification of Diet in Renal Disease equation 72.0 [56.7-89.3] versus 70.4 [54.5-85.3] ml/min, peak oxygen uptake 62.2 [50.7-74.1] versus 52.6 [41.8-64.3]% predicted, minute ventilation-to-carbon dioxide output slope 30.0 [26.9-34.4] versus 32.1 [28.0-38.0] in HFimpEF and pHFrEF, respectively (p < 0.001 for all). Cardiovascular mortality rates were 26.6 and 46.9 per 1000 person-years for HFimpEF and pHFrEF, respectively (p < 0.001). Kaplan-Meier analysis showed that HFimpEF had better a long-term prognosis compared with pHFrEF patients. After adjustment for variables differentiating HFimpEF from pHFrEF, except echocardiographic parameters, the Kaplan-Meier curves showed the same prognosis.

CONCLUSIONS

Heart failure with improved ejection fraction represents a peculiar group of HF patients whose clinical, laboratory, electrocardiographic, echocardiographic, and exercise characteristics parallel the recovery of systolic function. Nonetheless, these patients remain at risk for adverse outcome.

Does moderate hyperkalemia influence survival in HF? Insights from the MECKI score data base

BACKGROUND

The prognostic role of moderate hyperkalemia in reduced ejection fraction (HFrEF) patients is still controversial. Despite this, it affects the use of renin-angiotensin-aldosterone system inhibitors (RAASi) with therapy down-titration or discontinuation.

OBJECTIVES

Aim of the study was to assess the prognostic impact of moderate hyperkalemia in chronic HFrEF optimally treated patients.

METHODS AND RESULTS

We retrospectively analyzed MECKI (Metabolic Exercise test data combined with Cardiac and Kidney Indexes) database, with median follow-up of 4.2 [IQR 1.9-7.5] years. Data on K⁺ levels were available in 7087 cases. Patients with K⁺ plasma level ≥ 5.6 mEq/L and < 4 mEq/L were excluded. Remaining patients were categorized into normal >4 and < 5 mEq/L (n = 4826, 68%) and moderately high ≥5.0 and ≤ 5.5 mEq/L (n = 496, 7%) K⁺. Then patients were matched by propensity score in 484 couplets of patients. MECKI score value was 7% [IQR 3.1-14.1%] and 7.3% [IQR 3.4-15%] (p = 0.678) in patients with normal and moderately high K⁺ values while cardiovascular mortality events at two years follow-up were 41 (4.2%) and 33 (3.4%) (p = 0.333) in each group respectively.

CONCLUSIONS

Moderate hyperkalemia does not influence patients' outcome in a large cohort of ambulatory HFrEF patients.

Nonresponse to Acute Vasodilator Challenge and Prognosis in Heart Failure With Pulmonary Hypertension

BACKGROUND

An acute vasodilator challenge is recommended in patients with heart failure and pulmonary hypertension during heart transplant evaluation. The aim of the study was to assess which hemodynamic parameters are associated with nonresponsiveness to the challenge.

METHODS AND RESULTS

This study is a retrospective analysis of 402 patients with heart failure with pulmonary hypertension who underwent right heart catheterization and a pulmonary vasodilator challenge. Among the 140 who fulfilled the transplant guidelines eligibility criteria for the vasodilator challenge, 38 were responders and 102 nonresponders. At multivariable analysis, a diastolic blood pressure of <70 mm Hg, pulmonary vascular resistance of >5 Woods units, and pulmonary artery compliance of <1.2 mL/mm Hg were independently associated with poor response to vasodilator challenge (all P < .001). The presence of any 2 of these 3 conditions was associated with a 90% probability of being a nonresponder. The covariate-adjusted hemodynamic predictors of death in the entire population were a low baseline systolic blood pressure (P = .0017) and a low baseline right ventricular stroke work index (P = .0395).

CONCLUSIONS

In patients with heart failure and pulmonary hypertension, low pulmonary arterial compliance, high pulmonary vascular resistance, and low diastolic blood pressure predict the nonresponsiveness to acute vasodilator challenge whilst a poor right ventricular function predicts a dismal prognosis.

Clinical and prognostic impact of chronotropic incompetence in patients with hypertrophic cardiomyopathy

BACKGROUND

A blunted heart rate (HR) response is associated with an impaired peak oxygen uptake (pVO₂), a powerful outcome predictor in hypertrophic cardiomyopathy (HCM). The present multicenter study sought to determine the prognostic role for exercise-induced HR response in HCM.

METHODS

A total of 681 consecutive HCM outpatients on optimized treatment were recruited. The heart failure (HF) end-point was death due to HF, cardiac transplantation, NYHA III-IV class progression, HF worsening leading to hospitalization and severe functional deterioration leading to septal reduction. The sudden cardiac death (SCD) end-point included SCD, aborted SCD and appropriate implantable cardioverter defibrillator discharges.

RESULTS

During a median follow-up of 4.2 years (25-75th centile: 3.9-5.2), 81 patients reached the HF and 23 the SCD end-point. Covariates with independent effects on the HF end-point were left atrial diameter, left ventricular ejection fraction, maximal left ventricular outflow tract gradient and exercise cardiac power (ECP = pVO₂∗systolic blood pressure) (C-Index = 0.807) whereas the HCM Risk-SCD score and the ECP remained associated with the SCD end-point (C-Index = 0.674). When the VO₂-derived variables were not pursued, peak HR (pHR) re-entered in the multivariate HF model (C-Index = 0.777) and, marginally, in the SCD model (C-index = 0.656). A pHR = 70% of the maximum predicted resulted as the best cut-off value in predicting the HF-related events.

CONCLUSIONS

The cardiopulmonary exercise test is pivotal in the HCM management, however the pHR remains a meaningful alternative parameter. A pHR < 70% identified a HCM population at high risk of HF-related events, thus calling for a reappraisal of the chronotropic incompetence threshold in HCM.

Monotherapy and Dual Combination Therapies Based on Olmesartan: A Comprehensive Strategy to Improve Blood Pressure Control

Olmesartan medoxomil is an antihypertensive drug of the class of angiotensin II type 1 (AT1) receptor antagonists (or blockers), characterized by tight and prolonged binding to AT1 receptor compared to other molecules within the same class. These characteristics produce effective and sustained blood pressure reductions in hypertensive patients at different cardiovascular risk profile with a good tolerability profile. After a brief description of the pharmacological characteristics of olmesartan, we will provide a thorough overview of the clinical studies that investigated its efficacy and safety in the clinical management of hypertensive patients both in monotherapy and in dual combination therapies with either thiazide diuretics or calcium channel blockers. These studies demonstrated that olmesartan-based antihypertensive strategy may indeed provide sustained BP control over the 24-h period in a wide proportion of hypertensive patients, thus contributing to a substantial progress in hypertension management. Finally, since growing evidence suggest that olmesartan may also exert potential favourable effects at vascular level, thereby antagonizing the vascular inflammatory process involved in the development and progression of atherosclerosis, the main clinical studies addressing this issue will be also discussed.

QT spatial dispersion and sudden cardiac death in hypertrophic cardiomyopathy: Time for reappraisal

BACKGROUND

The 12-lead surface electrocardiographic (ECG) analysis is able to provide independent predictors of prognosis in several cardiovascular settings, including hypertrophic cardiomyopathy (HCM). The present single-center study investigated the possible ability of several ECG-derived variables in stratifying sudden cardiac death (SCD) risk and, possibly, in improving the accuracy of the 2014 European Society of Cardiology guidelines.

METHODS

A total of 221 consecutive HCM outpatients were recruited and prospectively followed. All of them underwent a full clinical and instrumental examination, including a 12-lead surface ECG to calculate the dispersion for the following intervals: QRS, Q-Tend (QT), Q-Tpeak (QTp), Tpeak-Tend (TpTe), J-Tpeak (JTp), and J-Tend (JT). The study composite end-point was SCD, aborted SCD, and appropriate implantable cardioverter defibrillator (ICD) interventions.

RESULTS

During a median follow-up of 4.4 years (25th-75th interquartile range: 2.4-9.4 years), 23 patients reached the end-point at 5-years (3 SCD, 3 aborted SCD, 17 appropriate ICD interventions). At multivariate analysis, the spatial QT dispersion corrected according to Bazett's formula (QTcd) remains independently associated to the study endpoint over the HCM Risk-SCD score (C-index 0.737). A QTcd cut-off value of 93ms showed the best accuracy in predicting the SCD endpoint within the entire HCM study cohort (sensitivity 56%, specificity 75%, positive predictive value 22%, negative predictive value 97%).

CONCLUSION

Our data suggest that the QTcd might be helpful in SCD risk stratification, particularly in those HCM categories classified at low-intermediate SCD risk according to the contemporary guidelines.

New therapies for arterial hypertension

Arterial hypertension is the most common chronic disease in developed countries and it is the leading risk factor for stroke, ischemic heart disease, congestive heart failure, chronic renal failure and peripheral artery disease. Its prevalence appears to be about 30-45% of the general population. Recent European guidelines estimate that up to 15-20% of the hypertensive patients are not controlled on a dual antihypertensive combination and they require three or more different antihypertensive drug classes to achieve adequate blood pressure control. The guidelines confirmed that diuretics, beta-blockers, calcium-channel blockers, angiotensin-converting enzyme inhibitors and angiotensin receptor blockers are suitable for the initiation and maintenance of antihypertensive treatment, either as monotherapy or in combination therapy. Very few antihypertensive agents have reached the market over the last few years, but no new therapeutic class has really emerged. The long-term adherence to cardiovascular drugs is still low in both primary and secondary prevention of cardiovascular diseases. In particular, the issue of compliance is persistently high in hypertension, despite the fixed-dose combination therapy. As a consequence, a cohort of high-risk hypertensive population, represented by patients affected by refractory and resistant hypertension, can be identified. Therefore, the need of controlling BP in high-risk patients may be addressed, in part, by the development of new drugs, devices and procedures that are designed to treat hypertension and comorbidities. In this review we will comprehensively discuss the current literature on recent therapeutic advances in hypertension, including both medical therapy and interventional procedures.

Inadequate RAAS suppression is associated with excessive left ventricular mass and systo-diastolic dysfunction

BACKGROUND

Inadequate suppression of renin-angiotensin-aldosterone system (RAAS) following postural maneuvers may have detrimental effects on cardiac structure and function. In this study, we aimed to appraise the clinical significance of this phenomenon by assessing its relation with inappropriate ventricular mass (ILVM), an adverse phenotype of LV remodeling and dysfunction.

METHODS

Both supine and upright plasma renin activity (PRA) and aldosterone concentrations (PAC) were measured in 115 young newly diagnosed hypertensive subjects. 24-h ambulatory blood pressure monitoring and echocardiographic evaluation including tissue Doppler imaging (TDI) were also performed. Patients were divided as follows: (1) normal PRA and PAC (N) (n = 63); (2) suppressible RAAS (SR) in supine position (n = 27); (3) not suppressible RAAS (NSR) (n = 25). ILVM was expressed as the observed/predicted LV mass ratio ×100 (%PLVM), while LV dysfunction (LVD) was identified by TDI-derived myocardial performance index (MPI).

RESULTS

NSR showed a higher prevalence of ILVM than SR and N. As compared with N and SR, NSR patients had reduced indices of systolic and diastolic function. MPI of the LV as well as prevalence of LVD was also significantly higher in the NSR group. Regression models showed that lack of RAAS suppression was independently associated with ILVM and LVD.

CONCLUSIONS

Prevalence of ILVM and LVD is higher in patients without clinostatic RAAS suppression. Our findings encourage the assessment of RAAS deregulation to better estimate individual cardiovascular risk in patients with arterial hypertension.

Latitude-correlated genetic polymorphisms: selection or gene flow?

Latitude-correlated polymorphisms can be due to either selection-driven evolution or gene flow. To discriminate between them, we propose an approach that studies subpopulations springing from a single population that have lived for generations at different latitudes and have had a low genetic admixture. These requirements are fulfilled to a large extent by Ashkenazi and Sephardi Jews. The original population lived at a latitude of 35 degrees N, where the Sephardis still live. The Ashkenazis, however, moved to a latitude of 50 degrees N, starting about 10 centuries ago. The present study examines 3 latitude-correlated polymorphisms: PGP, PGM1, and AHSG. We found that PGP*2 and AHSG*2 alleles most likely underwent selection-driven evolution, but that PGM1*ts allele was not similarly affected. Since temperature might have been considered a reasonable selective factor, we also studied a population living at >800 m above sea level from Aosta Valley (Italy).

Cooperative interactions between the central spindle and the contractile ring during Drosophila cytokinesis

We analyzed male meiosis in mutants of the chickadee (chic) locus, a Drosophila melanogaster gene that encodes profilin, a low molecular weight actin-binding protein that modulates F-actin polymerization. These mutants are severely defective in meiotic cytokinesis. During ana-telophase of both meiotic divisions, they exhibit a central spindle less dense than wild type; certain chic allelic combinations cause almost complete disappearance of the central spindle. Moreover, chic mutant spermatocytes fail to form an actomyosin contractile ring. To further investigate the relationships between the central spindle and the contractile ring, we examined meiosis in the cytokinesis-defective mutants KLP3A and diaphanous and in testes treated with cytochalasin B. In all cases, we found that the central spindle and the contractile ring in meiotic ana-telophases were simultaneously absent. Together, these results suggest a cooperative interaction between elements of the actin-based contractile ring and the central spindle microtubules: When one of these structures is disrupted, the proper assembly of the other is also affected. In addition to effects on the central spindle and the cytokinetic apparatus, we observed another consequence of chic mutations: A large fraction of chic spermatocytes exhibit abnormal positioning and delayed migration of asters to the cell poles. A similar phenotype was seen in testes treated with cytochalasin B and has been noted previously in mutants at the twinstar locus, a gene that encodes a Drosophila member of the cofilin/ADF family of actin-severing proteins. These observations all indicate that proper actin assembly is necessary for centrosome separation and migration.

Characterization of the opposite-strand genes from the mouse bidirectionally transcribed HTF9 locus

The mouse HTF9 locus contains two genes that are bidirectionally transcribed with opposite polarity from a shared CpG-rich island. Both genes were previously shown to be expressed in a housekeeping fashion in mouse. We have now determined the molecular organization of the genes over 12 kb surrounding the island. In addition, we show that the HTF9 locus resides in the proximal region of mouse chromosome 16. We have sequenced the cDNAs corresponding to both divergent transcripts. Both genes appear to code for novel proteins that are structurally unrelated to each other. Finally, we show that both genes are highly conserved and efficiently expressed in human cells.

Common and rare genetic variants of human red blood cell enzymes in Italy

In the present paper we report on new data of the frequency of common and rare variants in the Italian population for ADA, AK-1, 6-PGD, EsA, EsB, EsD, PGM-1, PGM-2, SOD-A, AcP, GPT, and PGI. Moreover we present a comprehensive review of the available data on the electrophoretic variants of red cell enzymes in Italians. We find a considerable degree of genetic heterogeneity between the various populations living in the Peninsula and between the population of the Peninsula and of Sardinia. We also find that the estimates of the average heterozygosity are considerably smaller for the population of Sardinia as compared to Peninsula and Sicily. Finally, we report on the occurrence of several uncommon enzyme variants, which overall frequency is very similar to previously reported estimates for North European populations (Harris et al. 1974).

Migration pattern and genetic marker distribution of the Afro-American population of Bluefields, Nicaragua

On a sample of the population of mixed African ancestry living in Bluefields, Nicaragua, the pattern of migration and the distribution of red cell and serum genetic markers have been studied. It is concluded that, in spite of a considerable level of internal and external migration, a distinctive genetic structure is maintained by the population. Moreover, a strongly negative assortative mating can be observed between people inhabiting the western and eastern areas of Nicaragua. It is estimated that most, if not all, of the genetic pool of the population is accounted for by a process of admixture between African and Indian peoples.

Genetic heterogeneity in Sardinia: 15 polymorphisms examined in 11 isolates

Blood group systems ABO, RH, MNS, KEL, FY, LU and P, red cell enzymes ACP1, PGM1, PGM2, ADA, DIA and PHI, serum markers GC, HP, IGHG1, IGHG3 and IGK were examined in about 900 individuals sampled in 11 Sardinian isolates. The genetic differentiation turned out to be relatively high and the relevance of selected and neutral genes has been evaluated.

Phosphoglycolate phosphatase polymorphism: gene frequencies in three Italian samples

The electrophoretic polymorphism of the PGP locus has been studied in about 1,700 Italians. The sample consisted of individuals from Viareggio (North-Central Italy), Rome (Central Italy) and Cagliari (Sardinia, Southern Italy). Comparison among the three groups showed a high degree of heterogeneity. The Sardinian sample was well differentiated from the other two concerning the frequencies of both the PGP3 and of PGP2 alleles. The frequency of the PGP1 allele varied from 0.900 (Viareggio) to 0.987 (Cagliari). The gene frequencies, together with those available for other European populations were plotted against the latitudes of the different localities sampled and fitted to a North-South cline.

Effects of propylthiouracil and methylmercaptoimidazole on thyroglobulin synthesis

The effect of 6-propyl-2-thiouracil (PTU), and 1-methyl-2-mercaptoimidazole (MMI) on thyroglobulin (Tg) biosynthesis has been studied in vivo and in vitro. In vivo experiments were performed in rats treated for 20 days with PTU or MMI, analyzing soluble and particulate, cold and 125I-labelled, Tg. Thyroglobulin biosynthesis was also investigated by in vitro experiments, incubating thyroid tissue with labelled amino acid and carbohydrate in the presence of antithyroid compounds. It has been found that in vivo antithyroid agents decrease the amount of soluble Tg and increase the proportion of particulate Tg. Tg from treated animals is poorly iodinated being mainly represented by its 12S subunit. In vitro studies demonstrate that PTU and MMI inhibit Tg biosynthesis which is impaired in the polypeptide synthesis as well as in carbohydrate chains addition. Thus the inhibition of the hormonogenetic processes induced by antithyroid treatment leading to a depressed iodinating activity also appears to be related to a significant impairment of the production of the Tg molecule, the specific iodine acceptor.