Stephen Lazarou

ORIGINAL RESEARCH—ENDOCRINOLOGY: Wide Variability in Laboratory Reference Values for Serum Testosterone

INTRODUCTION The laboratory determination of testosterone levels consistent with a diagnosis of hypogonadism is complicated by the availability of multiple testosterone assays and varying reference ranges. AIM To assess current laboratory practices regarding availability of testosterone assays and use of reference values. METHODS A telephone survey of 12 academic, 12 community medical laboratories, and one national laboratory. MAIN OUTCOME MEASURES Types of androgen assays offered and determination of reference values. RESULTS All of the academic and eight of the community centers performed total testosterone testing. Free testosterone was performed in-house by six of the 12 academic and one community center. Testing for bioavailable testosterone, free androgen index, and percent free testosterone was performed in-house by no more than two centers. There were eight and four different assays used for total and free testosterone, respectively. One national laboratory offered equilibrium dialysis measurement of free testosterone. Of the 25 labs, there were 17 and 13 different sets of reference values for total and free testosterone, respectively. The low reference value for total testosterone ranged from 130 to 450 ng/dL (350% difference), and the upper value ranged from 486 to 1,593 ng/dL (325% difference). Age-adjusted reference values were applied in four centers for total testosterone and in seven labs for free testosterone. All reference values were based on a standard statistical model without regard for clinical aspects of hypogonadism. Twenty-three of the 25 lab directors responded that clinically relevant testosterone reference ranges would be preferable to current standards. CONCLUSIONS Laboratory reference values for testosterone vary widely, and are established without clinical considerations.

Determining minimum effective anesthetic concentration of hyperbaric bupivacaine for spinal anesthesia.

We determined the minimum effective anesthetic concentration (MEAC) of bupivacaine for spinal anesthesia, defined as the median effective concentration at which a spinal anesthetic produces surgically equivalent anesthesia within 20 min of administration in 50% of human subjects. Two doses of spinal bupivacaine (7.5 mg and 10 mg) were administered to 45 volunteers (19–39 yr) in a randomized, double-blinded fashion. Hyperbaric bupivacaine solutions of 0.1% to 0.75% containing 8.25% dextrose were administered intrathecally and MEAC established by using the Dixon’s up-and-down method. Complete anesthesia was defined as: 1) pinprick anesthesia at or higher than T12; 2) anesthesia to transcutaneous tetanic electric stimulation (50 Hz at 60 mA for 5 s) in the knees; and 3) complete leg paralysis, all occurring in both lower extremities within 20 min of intrathecal injection. We found that the MEAC of spinal bupivacaine was 0.43% (95% confidence interval 0.24–0.62) when 10 mg was administered. At this dose, a concentration as low as 0.1% could provide complete anesthesia, but consistent blockade was obtained only with the 0.7% solution. The 7.5-mg dose failed to provide complete anesthesia consistently, even in the presence of 0.75% (maximum). The current commercially available 0.75% concentration of hyperbaric bupivacaine seems to be clinically optimal when 10 mg is used if complete bilateral lower extremity blockade is desired. Implications The value of the minimum effective anesthetic concentration for hyperbaric spinal bupivacaine is dose-dependent. Complete anesthesia can be achieved with smaller concentrations when the dose of spinal anesthetic is increased. The current commercially available 0.75% concentration of hyperbaric bupivacaine seems to be clinically optimal when 10 mg is used if complete bilateral lower extremity blockade is desired.

The Effect of Aging on Spermatogenesis and Pregnancy Outcomes

Until fairly recently, it had been assumed that paternal age had only a minor impact on reproductive outcome. Several recent provocative studies have raised the specter of a causal association between paternal age and significant medical conditions in the offspring. However, the observational nature of these studies leaves open the possibility that factors other than age itself may be responsible for observed results. This article reviews the available data on this topic, with an eye toward providing a basis for clinical counseling of the older man who wishes to have a child.

Y chromosome microdeletions and male infertility: who should be tested and why?

The previous issue of the BJU International presented a 7.4-year update of the ongoing bicalutamide Early Prostate Cancer (EPC) trial programme [1]. The authors conclude that bicalutamide is not useful in patients with localized disease, but recommend its use in patients with locally advanced disease, as it significantly improves progression-free survival (PFS) irrespective of standard care. The optimum use of hormonal therapy in prostate cancer is a fervently debated topic.