A. Broocks

Dieting causes menstrual irregularities in normal weight young women through impairment of episodic luteinizing hormone secretion

Thirteen healthy, normal weight young women were studied throughout a control cycle and a diet cycle, during which they lost 1kg per week on a vegetarian 800kcal diet. Blood was sampled daily in the morning, and at weekly intervals, collected at 10-minute intervals for 6 hours. Follicle growth was monitored by ultrasonic measurement. All subjects showed normal cyclic gonadal function during the control cycle. Cyclic gonadal function remained unaltered in two subjects during the diet cycle. No dominant follicle developed in seven others, while another four showed apparently normal follicular development but impaired progesterone secretion by the corpus luteum. Comparison of both cycles revealed that episodic luteinizing hormone (LH) secretion during the follicular phase was altered by dieting. Average LH concentrations and the frequency of episodic secretions were significantly reduced during the follicular phase but not during the luteal phase. Follicle-stimulating hormone was unaltered.

The influence of semistarvation-induced hyperactivity on hypothalamic serotonin metabolism

Male rats kept in a running wheel developed hyperactivity when food was restricted. Highest activity occurred around noon when food was given. Semistarved sedentary and ad lib fed sedentary and running rats served as controls. Five-hydroxyindole-acetic acid (5-HIAA) in the medial basal hypothalamus was lowest in the sedentary ad lib fed group. Running significantly increased 5-HIAA. Starvation likewise increased 5-HIAA. This effect was further enhanced by hyperactivity. When the circadian rhythm of serotonin (5-HT) and 5-HIAA was studied in the hypothalamus, a minimum of 5-HT as seen in semistarved sedentary and running rats around feeding time (noon). At this time 5-HIAA reached a maximum in the semistarved running rats while semistarved sedentary and ad lib fed rats showed no circadian pattern of 5-HIAA. These data indicate that serotonin turnover in the medial basal hypothalamus is increased as a consequence of semistarvation and hyperactivity.

Semistarvation-induced hyperactivity compensates for decreased norepinephrine and dopamine turnover in the mediobasal hypothalamus of the rat

Male Wistar rats were housed in running wheel cages and were restricted in their food intake, in order to reduce the initial body weight by 30% within 10 days. Rats increased their daily running up to distances between 7 and 11 km compared to the maximum 2.5 km in controls fed ad libitum. The hypothalamic noradrenaline (NE) turnover, as estimated by the concentration of the major metabolite MHPG, was significantly decreased in semistarved sedentary rats compared to controls. Hyperactivity resulted in marked elevation of NE turnover at all time points examined. Semistarvation-induced decreases of dopamine (DA) turnover as estimated by the concentrations of its major metabolite DOPAC, could also be compensated by hyperactivity. The circadian pattern of NE turnover parallels the pattern of running activity. MHPG levels at times of high activity were even higher than in controls fed ad libitum (p<0.01). The availability of the precursor tyrosine, as indicated by the ratio of plasma tyrosine to the large neutral amino acids, was significantly decreased in semistarvation (p<0.0001); hyperactivity caused a further decrease (p<0.001), indicating that tyrosine availability is not, under these conditions, a limiting factor for noradrenaline turnover. The combined influence of semistarvation and hyperactivity on central catecholamine turnover in the rat is discussed as an animal model for the effects of malnutrition and heavy exercise often observed in anorexia nervosa.

Endocrine findings in restrained eaters

Restrained (n = 9) and unrestrained eaters (n = 13) were selected from a group of healthy young women. Blood samples were collected overnight at half-hour intervals. Levels of cortisol, growth hormone, and glucose in both groups did not differ, while restrained eaters had significantly lower insulin values. After a standardized test meal of 500 kcal, restrained eaters had significantly lower norepinephrine values while insulin and glucose values did not differ from those of the unrestrained group. These findings indicate that restrained eating may have a biological basis.

Hyperactivity aggravates semistarvation-induced changes in corticosterone and triiodothyronine concentrations in plasma but not luteinizing hormone and testosterone levels.

Semistarvation over a ten-day period resulted in a weight loss of 30% in male Wistar rats, which had continuous access to a running wheel. The animals increased their activity up to 20 km per day. Controls fed ad lib increased activity only slightly (up to 2.3 km on day ten). Groups of semistarved and ad lib-fed sedentary rats were studied as controls. The circadian pattern of corticosterone (B), triiodothyronine (T3), luteinizing hormone (LH) and testosterone (T) was studied. Corticosterone was synergistically increased by semistarvation and exercise. The reduction of triiodothyronine by semistarvation was significantly greater in the running wheel group. Both luteinizing hormone and testosterone were significantly decreased by semistarvation. Hyperactivity did not result in additional suppression of LH and testosterone.

Serotonin turnover in rat brain during semistarvation with high-protein and high-carbohydrate diets

Serotonin (5-HT) and 5-hydroxyindolacetic acid (5-HIAA) were determined in seven brain regions of semistarved and control male rats. After semistarvation on a high carbohydrate diet serotonin turnover, as indicated by 5-HIAA/5-HT ratio, was increased in the total brain and several regions both three and 24 hours after the last meal. In contrast, after semistarvation on a high-protein diet serotonin turnover was decreased three hours after ingestion of the final meal, but increased 24 hours thereafter. Compulsary running wheel activity for one hour did not influence diet inducet changes in serotonin turnover. Alterations in plasma corticosterone during semistarvation were not related to changes in central serotonin turnover. Data suggest that the interaction of caloric restriction and diet composition determines serotonin turnover during semistarvation.

LUTEINIZING HORMONE AND FOLLICLE STIMULATING HORMONE SECRETION PATTERNS IN FEMALE ATHLETES WITH AND WITHOUT MENSTRUAL DISTURBANCES

Thirty‐one young female athletes and 13 age‐matched sedentary controls were studied throughout one menstrual cycle or over a 6 week period. Blood was sampled on 5 days per week. Episodic gonadotrophin secretion was measured in the early follicular phase and in the late luteal phase by blood sampling over a 12‐h period at 15‐min intervals. Eight athletes had anovulatory cycles, nine had impaired progesterone (P4) secretion during the luteal phase and 14 had normal cycles as judged from oestradiol (E2) and P4 plasma levels. Athletes with normal cycles had shorter cycles, lower E2 maxima at midcycle, and lower E2 and P4 concentrations during the luteal phase than had sedentary controls. Episodic luteinizing hormone (LH) secretion in the early follicular phase was significantly impaired in the anovulatory athletes: the average LH values over 12 h and the number of secretion episodes were significantly reduced. No significant changes were seen in follicle stimulating hormone secretion.

Influence of Hyperactivity on the Metabolism of Central Monoaminergic Neurotransmitters and Reproductive Function in the Semistarved Rat

The majority of young women associate a slim body image with attractiveness and are therefore motivated to restrain daily food intake according to a variety of dietary rules as presented in women’s magazines. Another factor that has proved to have an increasing impact on Western society’s lifestyle is the pursuit of physical fitness. Regular jogging and other forms of endurance training have become favorite recreational activities.

GONADOTROPHIN SECRETION IN THE SECOND HALF OF THE MENSTRUAL CYCLE: A COMPARISON OF WOMEN WITH NORMAL CYCLES, LUTEAL PHASE DEFECTS AND DISTURBED FOLLICULAR DEVELOPMENT

In order to study the relationship between episodic gonadotrophin secretion and alterations of ovarian hormone secretion, we examined women with normal menstrual cycles (n= 26), luteal phase defects (n= 10) or disturbed follicular oestradiol secretion (n= 8) as established by daily (except weekends) determinations of oestradiol and progesterone. Pulsatile gonadotrophin secretion was studied during the luteal phase or the second half of the menstrual cycle sampling at IS min intervals for 12 h. LH and FSH mean concentrations and LH pulse frequency were significantly (P<0.01) increased in the group with disturbed follicular development in the presence of decreased oestradiol (E2) and progesterone (P4) levels. In women with luteal phase defects mean LH and FSH concentrations and pulsatile LH secretion showed a nonsignificant trend to lower values in the presence of significantly decreased P4 concentrations during the luteal phase.

Consequences of Dieting and Exercise on Menstrual Function in Normal Weight Young Women

Weight-reducing diets typically provide amounts of micronutrients and proteins that are within the limits of common recommendations and do not cause the characteristic disease states due to shortage of an essential nutrient. Diet composition of macro-nutrients mostly deviates from usual weight maintenance diets, but varies widely. Caloric intake is always reduced and typically varies between zero and about 1200 kcal. The majority of women that use these diets are not obese. Most of them diet for cosmetic or professional reasons to conform with cultural ideals linking beauty to slimness. Some diet to obtain an optimal weight for athletic performance. In some women dieting represents a response to stressful life situations. And not infrequently dieting occurs in the context of psychiatric disorders such as anorexia nervosa, bulimia nervosa, and depression. In many of these situations dieting may occur together with increased exercise.