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Biomedical subjects

Gregory A Brown

Publications and source records attributed to Gregory A Brown.

6 recordsLinked to original sources
PubMed2006

Acute resistance exercise does not change the hormonal response to sublingual androstenediol intake.

Sublingual intake of 21.4 mg androstenediol increases serum testosterone concentrations whereas swallowing 200 mg androstenediol does not. The duration of increase in serum testosterone following sublingual androstenediol (SL-DIOL) is unknown. Resistance exercise (EX) following SL-DIOL may cause larger increases in serum estradiol concentrations than while at rest. This project evaluated the duration of change in, and the effects of acute EX on, the hormonal response to SL-DIOL. Six young resistance trained males consumed either placebo (PL) or SL-DIOL before a single session of EX or no exercise (Rest) in a random, double blind, crossover manner (for a total of four trials). Blood samples were collected before supplementation, and at 60, 120, 180, 240, 480, and 720 min post-supplementation, with the exercise occurring between 60 and 120 min. The serum [total testosterone] increased (P < 0.05) at 60 min similarly in SL-DIOL-EX and SL-DIOL-Rest by approximately 115%, and at 120 min by approximately 107% with no differences due to exercise. The serum [estradiol] increased (P < 0.05) similarly in SL-DIOL-EX and SL-DIOL-Rest by approximately 33% at 60 min and approximately 45% at 120 min, with no differences due to exercise. Serum [testosterone] returned to baseline by 240 min and serum [estradiol] returned to baseline by 720 min post-intake. These findings indicate that SL-DIOL acutely elevates serum testosterone and estradiol concentrations, that EX does not alter the endocrine response to SL-DIOL, and that the increases in serum estradiol last between 480 and 720 min while the increases in serum testosterone last <240 min following acute SL-DIOL intake.

Administration, Sublingual↗
PubMed2006

Teaching skeletal muscle adaptations to aerobic exercise using an American Physiological Society classic paper by Dr. Philip Gollnick and colleagues.

The use of primary research in the classroom enhances the critical thinking abilities of students. The present article describes a strategy for using the American Physiological Society classic paper "Enzyme activity and fiber composition in skeletal muscle of untrained and trained men" by Dr. Philip D. Gollnick and colleagues to enhance the students' ability to understand research, increase their knowledge of the adaptations to exercise, and learn computer skills in data analysis and presentation. By having students read, study, prepare graphs, and discuss the data from a classic paper, they gain an improved understanding of the factors that influence aerobic exercise ability. This study is especially useful for illuminating the exercise-specific differences in bioenergetic enzymes, muscle fiber type, and fitness characteristics that exist between untrained and trained individuals.

Adaptation, Physiological↗
PubMed2006

Testosterone prohormone supplements.

Testosterone prohormones such as androstenedione, androstenediol, and dehydroepiandrosterone (DHEA) have been heavily marketed as testosterone-enhancing and muscle-building nutritional supplements for the past decade. Concerns over the safety of prohormone supplement use prompted the United States Food and Drug Administration to call for a ban on androstenedione sales, and Congress passed the Anabolic Steroid Control Act of 2004, which classifies androstenedione and 17 other steroids as controlled substances. As of January 2005, these substances cannot be sold without prescription. Here, we summarize the current scientific knowledge regarding the efficacy and safety of prohormone supplementation in humans. We focus primarily on androstenedione, but we also discuss DHEA, androstenediol, 19-nor androstenedione, and 19-nor androstenediol supplements. Contrary to marketing claims, research to date indicates that the use of prohormone nutritional supplements (DHEA, androstenedione, androstenediol, and other steroid hormone supplements) does not produce either anabolic or ergogenic effects in men. Moreover, the use of prohormone nutritional supplements may raise the risk for negative health consequences.

Androstenediols↗
PubMed2004

Urinary excretion of steroid metabolites after chronic androstenedione ingestion.

Urinary steroid excretion after androstenedione intake has been examined after a single dose of 50 mg and single doses of 100 or 300 mg/d for 7 d. We evaluated the effects of 28 d of 100 mg three times a day (t.i.d.) androstenedione intake on urinary steroid excretion. Twenty healthy men, ages 30-39 yr (33.5 +/- 0.6), consumed 100 mg androstenedione t.i.d. or placebo for 28 d. Urine samples were analyzed for testosterone, epitestosterone, androsterone, and etiocholanolone via HPLC/tandem mass spectrometry on d 0 and 28. Androstenedione intake increased (P < 0.05) urinary testosterone 35.1 +/- 10.5 ng/ml vs. 251.6 +/- 87.5 ng/ml, epitestosterone 35.3 +/- 8.8 ng/ml vs. 99.7 +/- 28.7 ng/ml, androsterone 2,102 +/- 383 ng/ml vs. 15,767 +/- 3,358 ng/ml, and etiocholanolone 1,698 +/- 409 ng/ml vs. 11,329 +/- 2,656 ng/ml (means +/- se). Although the testosterone to epitestosterone ratio (T/E) tended to increase with androstenedione intake (1.2 +/- 0.3 vs. 4.0 +/- 1.6; P = 0.12), only one subject had a urinary T/E greater than the current Olympic criteria (>6.0) for a positive drug test. Chronic intake of 100 mg androstenedione t.i.d. increases the urinary excretion of steroid metabolites. Due to inconsistent increases in the T/E ratio, the T/E ratio may not effectively detect androstenedione use.

Administration, Oral↗
PubMed2002

Acute hormonal response to sublingual androstenediol intake in young men.

The effectiveness of orally ingested androstenediol in raising serum testosterone concentrations may be limited because of hepatic breakdown of the ingested androgens. Because androstenediol administered sublingually with cyclodextrin bypasses first-pass hepatic catabolism, we evaluated the acute hormonal response to sublingual cyclodextrin androstenediol supplement in young men. Eight men (22.9 +/- 1.2 yr) experienced in strength training consumed either 20 mg androstenediol in a sublingual cyclodextrin tablet (Sl Diol) or placebo (Pl) separated by at least 1 wk in a randomized, double-blind, crossover manner. Blood samples were collected before supplementation and at 30-min intervals for 3 h after supplementation. Serum hormone concentrations did not change with Pl. Serum androstenedione concentrations were increased (P < 0.05) above baseline (11.2 +/- 1.1 nmol/l) with Sl Diol from 60 to 180 min after intake and reached a peak concentration of 25.2 +/- 2.9 nmol/l at 120 min. Serum free testosterone concentrations were increased from 86.2 +/- 9.1 pmol/l with Sl Diol from 30 to 180 min and reached a peak concentration of 175.4 +/- 12.2 pmol/l at 60 min. Serum total testosterone concentrations increased above basal (25.6 +/- 2.3 nmol/l) from 30 to 180 min with Sl Diol and reached a peak concentration of 47.9 + 2.9 nmol/l at 60 min. Serum estradiol concentrations were elevated (P < 0.05) above baseline (0.08 +/- 0.01 nmol/l) from 30 to 180 min with Sl Diol and reached 0.14 +/- 0.02 nmol/l at 180 min. These data indicate that sublingual cyclodextrin androstenediol intake increases serum androstenedione, free testosterone, total testosterone, and estradiol concentrations.

Administration, Sublingual↗