Thomas C. Rotkis

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 subjects 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.

THE EFFECT OF AN ACUTE BOUT OF EXERCISE ON SELECTED PULMONARY FUNCTION MEASUREMENTS.

The purpose of this study was to determine and follow the effect of an acute bout of exercise on residual volume (RV) and other pulmonary function measurements over a 24-h post-exercise period, and to evaluate the effect on subsequent body composition calculations. Selected pulmonary function measurements of 12 male college students were collected prior to exercise at 5, 15, and 30 min, and at 1, 2, and 24 h post-exercise. RV was significantly (P less than 0.01) increased 20.8% (260 ml), 16.8% (210 ml) and 12.0% (150 ml) at 5, 15, and 30 min post-exercise, respectively. Total lung capacity (TLC) was significantly (P less than 0.01) increased 2.7% (190 ml) and 2.3% (160 ml) at 5 and 15 min post-exercise, respectively. Subsequent body composition calculations, using the post-exercise RV data, resulted in significantly (P less than 0.01) lower relative body fat measures, as compared to the pre-exercise value, through 30 min of recovery. In conclusion, our data demonstrate apparent increases in RV and TLC immediately following maximal treadmill exercise; these measurements remained significantly increased over pre-exercise values, through 30 and 15 min of recovery, respectively. It is recommended that the RV measurement and the actual hydrostatic weighing procedure not be separated by an acute bout of exercise, and that protocols for long-term studies be standardized.

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 subjects 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.

Impaired gonadotropin responses to gonadotropin-releasing hormone stimulation in endurance-trained women**Supported by the Zuckerman Fund, Tucson, Arizona.

The effects of endurance running on body composition, menstrual cycles, and gonadotropins were studied in 19 healthy, young, regularly menstruating women. Midfollicular plasma concentrations of unstimulated and gonadotropin-releasing hormone (GnRH)-stimulated luteinizing hormone and follicle-stimulating hormone were examined at baseline and after each subjects weekly mileage had increased 30 miles (delta 30) and 50 miles (delta 50) above baseline. Mean +/- standard error of the mean unstimulated luteinizing hormone and follicle-stimulating hormone did not change significantly. GnRH-stimulated luteinizing hormone was 76.3 +/- 22.0 micrograms/min/ml at baseline and declined to 20.2 +/- 4.5 micrograms/min/ml at delta 50 (P less than 0.02). GnRH-stimulated follicle-stimulating hormone was 28.4 +/- 7.0 micrograms/min/ml at baseline and declined to 9.6 +/- 2.1 micrograms/min/ml at delta 50 (P less than 0.02). There were no significant correlations between changes in body composition and changes in gonadotropin responses. Eighteen subjects developed oligomenorrhea.