Biomedical subjects

P Stanforth

Publications and source records attributed to P Stanforth.

5 recordsLinked to original sources

PubMed1984

Thyroidal changes associated with endurance training in women.

The associations between endurance training, body composition, and the pituitary-thyroid axis were studied in 17 healthy, young women. Body composition and plasma concentrations of T4, T3, rT3, resin T3 uptake, TSH, and TRH-stimulated TSH were examined at baseline and after each subject's weekly distance had increased 48 km (delta 48) and 80 km (delta 80) above baseline. Total body weight did not change at delta 48 or delta 80. Mean (+/- SE) lean weight in kg increased from 42.9 +/- 1.2 at baseline to 44.8 +/- 1.2 at delta 80 (P = 0.002). We have reported previously that at delta 48 the subjects had evidence of mild thyroidal impairment, which consisted of decreased T3 and rT3, and an exaggerated TSH response to TRH. With more prolonged training (delta 48 to delta 80) there were significant increases in T4, rT3, and unstimulated TSH, while the ratios of T4/rT3 and T3/rT3 and the TSH response to TRH decreased significantly. Some of the thyroidal changes that occurred between delta 48 and delta 80 are similar to those seen in other stressful non-thyroidal conditions.

Adult↗

PubMed1983

Sex steroids and endurance running in women.

The effects of endurance training on body composition, menstrual cycles, and sex steroids were studied in 19 healthy, regularly menstruating women. Body composition and midfollicular plasma concentrations of estradiol (E2), estrone (E1), and testosterone (T) were examined at baseline and after each subject's weekly mileage had increased 30 miles (delta 30) and 50 miles (delta 50) above baseline. Total body weight did not change, but the subjects became leaner. Mean +/- standard error of the mean E2 decreased from 70.6 +/- 13.9 pg/ml at baseline to 33.6 +/- 4.8 pg/ml at delta 50 (P = 0.03). Mean E1 decreased progressively, but not significantly, while T did not change. Eighteen women developed menstrual changes (mainly oligomenorrhea), but not amenorrhea. Endurance running in women results in frequent menstrual dysfunction and is associated with a significant decrease in E2 concentrations.

Adult↗

PubMed1982

Evidence for mild thyroidal impairment in women undergoing endurance training.

The effects of endurance training on body composition and the pituitary-thyroid axis were studied in 29 healthy, young (mean age, 28.7 yr), regularly menstruating women. Women who were initially jogging a mean of 13.5 miles/week were selected for this study to minimize dropouts. Body composition, measured by hydrostatic weighing, and nonfasting plasma concentrations of T4, T3, rT3, TSH, and TRH-stimulated TSH, measured by RIA, were examined initially and after each subject's weekly mileage had increased to 30 miles ( delta 30) for at least 2 consecutive weeks. Two subjects were found to have compensated primary hypothyroidism and were not included in the subsequent data analysis. At delta 30, mean body weight did not change, mean fat weight decreased (- 1.02 kg; P less than 0.005), and mean lean weight increased (+0.75 kg; P less than 0.05). T4 and unstimulated TSH did not change. However, mean (+/-SE) T3 decreased from 107.2 +/- 4.4 to 97.9 +/- 3.4 ng/dl (P less than 0.025), and mean rT3 decreased from 170.9 +/- 13.9 to 154.6 +/- 13.2 pg/ml (P less than 0.025). The decreases in T3 and rT3 were accompanied by significantly greater TSH responses to TRH stimulation [mean (+/-SE) area under TSH curve, 1381.4 +/- 123 vs. 1712.8 +/- 202 micron IU/ml.min; P less than 0.01]. These results indicate that physically active women who undergo additional endurance training 1) become more lean without a change in total weight, and 2) have changes in T3, rT3, and TRH-stimulated TSH indicative of mild thyroidal impairment.

Adipose Tissue↗

PubMed1982

Prolactin responses, menstrual cycles, and body composition of women runners.

Fourteen young women with normal menses participated in an endurance running program to investigate the effects of physical training on menstrual function, plasma PRL, and body composition. Body composition, measured by hydrostatic weighing, and PRL (basal and TRH-stimulated ) were determined initially and after each subject had increased her weekly mileage by 30 miles (delta 30) and 50 miles (delta 50). Mean (+/- SEM) total body weight did not change, but the subjects became significantly leaner (relative fat, 25.5 +/- 1.3% at baseline vs. 22.4 +/- 0.9% at delta 50; P less than 0.02). Thirteen women developed menstrual changes (mainly oligomenorrhea), but not amenorrhea. Mean (+/- SEM) unstimulated PRL levels were 16.8 +/- 3.1%, 16.9 +/- 2.4, and 11.5 +/- 2.1 ng/ml at baseline, delta 30, and delta 50, respectively (P less than 0.03 at delta 50 compared to baseline and delta 30). Mean ( +/- SEM) integrated TRH-stimulated PRL responses increased from 5002 +/- 462 ng/ml.min at baseline to 5748 +/- 609 mg/ml.min at delta 30 and 6535 +/- 552 ng/ml.min at delta 50, and were significantly different from one another (F = 4.01; P less than 0.04). Endurance training, without total body weight loss or extreme leanness, results in frequent menstrual dysfunction. Other authors have shown that young female athletes have an increased PRL response to acute exercise compared to nonathletes. One mechanism responsible for menstrual dysfunction in endurance-trained women may be frequent and exaggerated PRL responses to exercise and other stimuli.

Adult↗

PubMed1981

High density lipoprotein cholesterol and body composition of female runners.

Twenty-two women participating in an endurance running program had determinations of body composition, of plasma total cholesterol (TC) and HDL cholesterol (HDLC) concentrations before and after increasing their running by 30 miles/wk. Mean total body weight, fat weight and relative body fat showed significant decreases, while mean lean weight significantly increased. Mean HDLC increased 5 mg/dl (p less than 0.01). Although increases of HDLC correlated with increases in lean weight, exercise per se appears to increase HDLC of women.

Adult↗