Clinical Briefs
By Louis Kuritzky, MD, Clinical Assistant Professor, University of Florida, Gainesville. Dr. Kuritzky is a consultant for GlaxoSmithKline and is on the speaker's bureau of GlaxoSmithKline, 3M, Wyeth-Ayerst, Pfizer, Novartis, Bristol-Myers Squibb, AstraZeneca, Jones Pharma, and Boehringer Ingelheim.
Erectile Dysfunction is a CVD Predictor
Erectile dysfunction (ED) most commonly reflects endothelial dysfunction of the corpora cavernosa. Because the risk factors for ED have been determined to be the same as those for cardiovascular disease (CVD), the concept that ED might actually be a predictor for CVD has garnered some support.
The Krimpen Study is a prospective observational study of men (n=3,924) between the ages of 50-75 residing in Krimpen, the Netherlands. From this population, all men aged 50-70 years responded to a question about erectile function. Men who were free of CVD at baseline (n=1,248) were followed for a mean of 6.3 years to compare the rate of CVD events in men reporting ED vs those without. Framingham risk scores were calculated at enrollment. Because this study sought to identify the relationship between ED and CVD, men with incident urologic disorders commonly associated with ED (eg, prostatectomy) were excluded.
After 7,945 person-years of follow up, the hazard ratio for CVD events among men with ED was 1.6 compared to men without ED at baseline. Men with the most severe ED had an even greater risk for CVD (hazard ratio = 2.6). The risk for CVD in this population was independent of Framingham risk score. This study confirms previous observations that ED is a predictor of CVD risk. Clinicians should address the CVD risk profile of men presenting with ED, even in the absence of other manifest vascular disease.
Schouten BWV, et al. Int J Impotence Research. 2008;20:92-99.
Does Traditional Thyroid Replacement (Levothyroxine) Adequately Restore T3?
Most circulating triiodothy- ronine (T3) is created by peripheral conversion of levothyroxine (T4), although the thyroid gland does directly produce 15-20% of plasma T3. Hypothyroidism is generally treated solely with T4 replacement, providing sufficient substrate for conversion to T3 and to consistently restore the euthyroid state as measured by TSH normalization. Previous trials of "dual thyroid replacement" (combinations of T3 and T4) have not been convincingly advantageous. With post-thyroidectomy, even though TSH is normalized with levothyroxine monotherapy, the question remains whether T3 restoration is truly adequate, given that the thyroid gland is no longer present to create its typical 15% of total T3. One way to assess this is to compare the T3 levels in subjects pre-and-post thyroidectomy who receive levothyroxine replacement.
Prior to thyroidectomy, 50 euthyroid subjects had measurement of T3 and T4. After sufficient levothyroxine replacement to restore euthyroidism (as assessed by TSH < 4.5 mIU/L), serum T3 and T4 were compared to pre-surgical levels.
Compared to pre-surgery baseline, levothyroxine replacement resulted in essentially unchanged T3 levels. However, the T4 levels attained, while still normal, were 33% higher than pretreatment.
T3 levels provided by traditional levothyroxine treatment are comparable to those seen in the euthyroid state; the authors reflect that the higher (albeit still therapeutic) T4 levels seen with levothyroxine replacement may be necessary to ensure adequate T3.
Jonklaas J, et al. JAMA. 2008;299(7):769-777.
Accuracy of Modern Glucose Meters
Both the AAFP and the ADA recommend self-monitoring of blood glucose (SMBG) as an integral component of overall diabetes disease management. Accuracy of SMBG must be assured in order to confidently modulate interventions effectively.
Because capillary blood (eg, fingerstick) glucose is 10-15% lower than venous plasma glucose, most monitors present their results corrected to venous glucose levels. The ADA criteria for accuracy suggest that future systems should provide results within 10% of reference standard within the glucose range of 30-400 mg/dL, although currently available devices are subject to a slightly more tolerant 15% variability.
A metric called the Clarke Error Grid (CEG) segments SMBG results as compared to a reference laboratory into multiple zones: Zone A includes clinically accurate results which should lead to clinically correct treatment; Zone B includes results that deviate by 20% or more from reference standards, but results so-obtained would result in no treatment change or benign treatment changes. Zones C, D, and E are misreadings of sufficient inaccuracy that they could result in meaningfully inappropriate treatment.
Detailed results from 172 patients tested with the OneTouch Ultra 2 show that SMBG results fall within Zone A 99% of the time, and no results were in Zone C, D, or E. Similar findings have been determined for the Ascensia Confirm, the Liberty, the EasyTouch, and OneTouch Ultra.
The authors further explain the most common source of SMBG errors: user error. But clinicians should be reassured that when used properly, currently available SMBG devices are remarkably accurate and unlikely to lead to inappropriate treatment.
Bergenstal RM. Insulin. 2008;3:4-14.
Erectile dysfunction (ED) most commonly reflects endothelial dysfunction of the corpora cavernosa. Because the risk factors for ED have been determined to be the same as those for cardiovascular disease (CVD), the concept that ED might actually be a predictor for CVD has garnered some support.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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