Jiaxiu He

Testosterone Threshold Levels and Lean Tissue Mass Targets Needed to Enhance Skeletal Muscle Strength and Function: The HORMA Trial

BACKGROUND In the HORMA (Hormonal Regulators of Muscle and Metabolism in Aging) Trial, supplemental testosterone and recombinant human growth hormone (rhGH) enhanced lean body mass, appendicular skeletal muscle mass, muscle performance, and physical function, but there was substantial interindividual variability in outcomes. METHODS One hundred and twelve men aged 65-90 years received testosterone gel (5 g/d vs 10 g/d via Leydig cell clamp) and rhGH (0 vs 3 vs 5 μg/kg/d) in a double-masked 2 × 3 factorial design for 16 weeks. Outcomes included lean tissue mass by dual energy x-ray absorptiometry, one-repetition maximum strength, Margaria stair power, and activity questionnaires. We used pathway analysis to determine the relationship between changes in hormone levels, muscle mass, strength, and function. RESULTS Increases in total testosterone of 1046 ng/dL (95% confidence interval = 1040-1051) and 898 ng/dL (95% confidence interval = 892-904) were necessary to achieve median increases in lean body mass of 1.5 kg and appendicular skeletal muscle mass of 0.8 kg, respectively, which were required to significantly enhance one-repetition maximum strength (≥ 30%). Co-treatment with rhGH lowered the testosterone levels (quantified using liquid chromatography-tandem mass spectrometry) necessary to reach these lean mass thresholds. Changes in one-repetition maximum strength were associated with increases in stair climbing power (r = .26, p = .01). Pathway analysis supported the model that changes in testosterone and insulin-like growth factor 1 levels are related to changes in lean body mass needed to enhance muscle performance and physical function. Testosterones effects on physical activity were mediated through a different pathway because testosterone directly affected Physical Activity Score of the Elderly. CONCLUSIONS To enhance muscle strength and physical function, threshold improvements in lean body mass and appendicular skeletal muscle mass are necessary and these can be achieved by targeting changes in testosterone levels. rhGH augments the effects of testosterone. To maximize functional improvements, the doses of anabolic hormones should be titrated to achieve target blood levels.

Severe Air Pollution and Labor Productivity: Evidence from Industrial Towns in China

We examine day-to-day fluctuations in worker-level output over 15 months for a panel of 98 manufacturing workers at a plant located in an industrial city in Hebei province, north China. Long-term workers earn piece-rate wages, with no base pay or minimum pay, for homogeneous tasks performed over fixed 8-hour shifts. Over the sample period, ambient fine-particle (PM2.5) mass concentrations measured at an outdoor air monitor located 2 km from the plant ranged between 10 and 773 micrograms per cubic meter (

Abdominal Obesity Contributes to Neurocognitive Impairment in HIV Infected Patients with Increased Inflammation and Immune Activation

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Durability of the effects of testosterone and growth hormone supplementation in older community-dwelling men: the HORMA Trial

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Testosterone Supplementation Improves Carbohydrate and Lipid Metabolism in Some Older Men with Abdominal Obesity

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Cardiometabolic risks during anabolic hormone supplementation in older men

, 8-hour means), variation that is an order of magnitude larger than what is observed in the rich world today. We document large reductions in productivity, of the order of 15\%, over the first 200

Whole-body and muscle protein metabolism are not affected by acute deviations from habitual protein intake in older men: the Hormonal Regulators of Muscle and Metabolism in Aging (HORMA) Study

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Abating Exposure to Diesel Exhaust in Developing Countries: Evidence from Sao Paulo

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Value of measuring muscle performance to assess changes in lean mass with testosterone and growth hormone supplementation

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Periodized resistance training with and without supplementation improve body composition and performance in older men

rise in PM2.5 concentrations. Starting at the sample minimum, the marginal effect of fine-particle pollution on output starts at about a 1\% drop per 10