Testosterone, Free and Total, 36170X LC/MS/MS Clinical Use Clinical Background • Assess androgen status in male hypo- Most testosterone is transported in gonadism; female hirsutism, viriliza- blood by sex hormone binding tion, acne, and amenorrhea; or in globulin (SHBG). Free testosterone pediatric patients is the small amount of testosterone circulating unbound. Blood Reference Range testosterone levels are dependent on Free Free rates of production, interconversion, Men % pg/mL metabolic clearance, and SHBG 18-69 y 1.5-2.2 35.0-155.0 concentration. SHBG levels are 70-89 y 1.5-2.2 30.0-135.0 altered by medications, disease, sex Women steroids, and insulin. SHBG increases 18-69 y 0.5-2.0 0.1-6.4 with age in men and decreases with 70-89 y 0.5-2.0 0.2-3.7 androgen excess in hirsute women. Pregnancy Thus, determination of free 1st trimester 0.15-0.66 0.5-6.0 testosterone more accurately reflects 2nd trimester 0.10-0.34 0.2-3.1 the level of bioactive testosterone than 3rd trimester 0.15-0.51 0.2-4.1 measurements of total testosterone Children, males and offers greater sensitivity in 5-9 y 0.44-1.78 <5.3 diagnosis of hypogonadism in 10-13 y 0.53-3.33 0.7-52.0 aging men and evaluation of mildly 14-17 y 1.05-2.91 18.0-111.0 hyperandrogenemic women. Children, females In general, total testosterone by ICMA, 5-9 y 0.28-1.81 0.2-5.0 a less technically demanding and 10-13 y 0.36-3.16 0.1-7.4 more economical procedure, is 14-17 y 0.41-2.34 0.5-3.9 satisfactory for screening potential See Testosterone, Total (Women, Children, male hypogonadism. The Endocrine Hypogonadal Males), LC/MS/MS for total Society has stated that ICMA or other testosterone reference ranges. "direct" assays are unreliable for diagnosing patients with low levels Interpretive Information (eg, <300 ng/dL) of testosterone. • Polycystic ovarian disease Method • Hyperthecosis Total Testosterone • Cushing’s disease • Liquid chromatography tandem • Congenital adrenal hyperplasia mass spectrometry (LC/MS/MS) • Precocious puberty • Analytical sensitivity: 1 ng/dL • Androgen resistance Free Testosterone • Hypogonadism • Tracer equilibrium dialysis, calculation • P-450c17 enzyme deficiency Specimen Requirements • Delayed puberty in boys 0.9 mL refrigerated serum (no additive • Gonadotropin deficiency red top tube); 0.38 mL minimum • Testicular defects SST red top unacceptable 168.