Dihydrotestosterone: Biochemistry, Physiology, and Clinical Implications of Elevated Blood Levels.

Benefits associated with lowered serum DHT levels after 5α-reductase inhibitor (5AR-I) therapy in men have contributed to a misconception that circulating DHT levels are an important stimulus for androgenic action in target tissues (e.g., prostate). Yet evidence from clinical studies indicates that intracellular concentrations of androgens (particularly in androgen-sensitive tissues) are essentially independent of circulating levels. To assess the clinical significance of modest elevations in serum DHT and the DHT/testosterone (T) ratio observed in response to common T replacement therapy, a comprehensive review of the published literature was performed to identify relevant data. Although the primary focus of this review is about DHT in men, we also provide a brief overview of DHT in women. The available published data are limited by the lack of large, well-controlled studies of long duration that are sufficiently powered to expose subtle safety signals. Nonetheless, the preponderance of available clinical data indicates that modest elevations in circulating levels of DHT in response to androgen therapy should not be of concern in clinical practice. Elevated DHT has not been associated with increased risk of prostate disease (e.g., cancer or benign hyperplasia) nor does it appear to have any systemic effects on cardiovascular disease safety parameters (including increased risk of polycythemia) beyond those commonly observed with available T preparations. Well-controlled, long-term studies of transdermal DHT preparations have failed to identify safety signals unique to markedly elevated circulating DHT concentrations or signals materially different from T.

Specificity and predictive value of circulating testosterone assessed by tandem mass spectrometry for the diagnosis of polycystic ovary syndrome by the National Institutes of Health 1990 criteria.

OBJECTIVE: To determine whether liquid chromatography-tandem mass spectrometry (LC-MS/MS) determination of total (TT) and free (FT) testosterone is more specific than extraction chromatography-radioimmunoassay (RIA) for distinguishing women with polycystic ovary syndrome (PCOS) from controls and whether differing cutoff values should be used depending on the setting. DESIGN: Prospective case-control cohort study. SETTING: Tertiary care center and reference laboratory. INTERVENTION(S): Blood sampling. PATIENT(S): One hundred patients with PCOS and 100 controls. MAIN OUTCOME MEASURE(S): Circulating TT measured by RIA and LC-MS/MS and FT measured by equilibrium dialysis using RIA or LC-MS/MS-generated TT values. RESULT(S): T measurement by RIA and LC-MS/MS similarly differentiated patients with PCOS from controls; detection of PCOS was higher for FT for both methods. TT values demonstrated greater overlap between patients with PCOS and controls than did FT for both RIA (80% vs. 42% overlap) and LC-MS/MS (52% vs. 67% overlap). A lower cutoff value by LC-MS/MS was better suited for the study of patients seen in the clinical (referred) setting (35 and 4.0 ng/dL for TT and FT, respectively) than in the screening of a general population (50 and 5.0 ng/dL for TT and FT, respectively). CONCLUSION(S): Extraction chromatography-RIA and LC-MS/MS measurements of T have similar performance for differentiating patients with PCOS from healthy controls; LC-MS/MS may be preferable given its relative ease of automation. Compared with FT, measurement of TT has relatively limited value for distinguishing PCOS from normal. Finally, different cutoff values should be considered depending on the clinical/investigative setting, with higher values being used in the study of biased (e.g., clinical or referred) populations.

Well differentiated follicular thyroid neoplasia: impact of molecular and technological advances on detection, monitoring and treatment.

Our understanding of the molecular mechanisms responsible for follicular thyroid cell oncogenesis has been advanced significantly in recent years. Specific genetic alterations and the molecular pathways they affect have been associated with particular histologic subtypes of well-differentiated thyroid cancer and are now being evaluated for their utility as clinical tools with diagnostic, prognostic and even therapeutic relevance. This paper focuses on the most common and clinically relevant genetic alterations shown to be consistently associated with well-differentiated thyroid carcinoma. We review the impact of recent molecular and technological advances on thyroid cancer standard of care and the practice of clinical medicine.

Validation of a total testosterone assay using high-turbulence liquid chromatography tandem mass spectrometry: total and free testosterone reference ranges.

Accurate measurement of testosterone concentration is of critical importance when diagnosing and treating male hypogonadism, congenital adrenal hyperplasia, premature or delayed puberty, and androgen excess in polycystic ovary syndrome or other virilizing conditions. However, some assays have inherent limitations and biases that affect measurement of low-testosterone values. Therefore, we developed a highly specific online mass spectrometry method. Sera were extracted online using high-turbulence flow liquid chromatography coupled to analytical HPLC and atmospheric pressure chemical ionization tandem mass spectrometry (HTLC-APCI-MS/MS). Analyte ions were monitored by multiple reaction monitoring (MRM). Total analysis time was 1.15 min per sample when using the multiplexing system. Testosterone concentrations were measured directly from 150 microL of serum or plasma without derivatization or liquid-liquid extraction. The lower limit of quantification was 0.3 ng/dL, and the assay was linear up to 2000 ng/dL. The method compared very well with an established RIA: y=1.02x+1.5, r(2)=0.994. Comparison with a platform immunoassay confirmed the previously reported ICMA positive bias at low concentrations. Male and female adult and pediatric reference ranges were developed for this very sensitive and accurate high-throughput LC-MS/MS method. This method is suitable for measuring the expected low-testosterone concentrations seen in women, children, and hypogonadal males and for monitoring testosterone suppressive therapy in prostate cancer patients.

Ion mobility analysis of lipoprotein subfractions identifies three independent axes of cardiovascular risk.

OBJECTIVE: Whereas epidemiological studies show that levels of low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) predict incident cardiovascular disease (CVD), there is limited evidence relating lipoprotein subfractions and composite measures of subfractions to risk for CVD in prospective cohort studies. METHODS AND RESULTS: We tested whether combinations of lipoprotein subfractions independently predict CVD in a prospective cohort of 4594 initially healthy men and women (the Malmö Diet and Cancer Study, mean follow-up 12.2 years, 377 incident cardiovascular events). Plasma lipoproteins and lipoprotein subfractions were measured at baseline with a novel high-resolution ion mobility technique. Principal component analysis (PCA) of subfraction concentrations identified 3 major independent (ie, zero correlation) components of CVD risk, one representing LDL-associated risk, a second representing HDL-associated protection, and the third representing a pattern of decreased large HDL, increased small/medium LDL, and increased triglycerides. The last corresponds to the previously described "atherogenic lipoprotein phenotype." Several genes that may underlie this phenotype-CETP, LIPC, GALNT2, MLXIPL, APOA1/A5, LPL-are suggested by SNPs associated with the combination of small/medium LDL and large HDL. CONCLUSIONS: PCA on lipoprotein subfractions yielded three independent components of CVD risk. Genetic analyses suggest these components represent independent mechanistic pathways for development of CVD.