Decreased serum leptin in bulimia nervosa

Associations between bone mineral density, body composition and amenorrhoea in females with eating disorders: a systematic review and meta-analysis

BACKGROUND

Lower bone mineral density (BMD) increases the risk of osteoporosis in individuals with eating disorders (EDs), particularly women with anorexia nervosa (AN), making them susceptible to pain and fractures throughout adulthood. In AN, low weight, hypothalamic amenorrhoea, and longer illness duration are established risk factors for low BMD, and in people with other EDs a history of AN seems to be an important risk factor for low BMD.

PURPOSE

To conduct a systematic review and meta-analysis of BMD in individuals with EDs, including AN, bulimia nervosa (BN), binge-eating disorder (BED) and other specified feeding or eating disorders (OSFED) compared to healthy controls (HC).

METHODS

Following PRISMA guidelines, electronic databases were reviewed and supplemented with a literature search until 2/2022 of publications measuring BMD (dual-energy X-ray absorptiometry or dual photon absorptiometry) in females with any current ED diagnosis and a HC group. Primary outcomes were spine, hip, femur and total body BMD. Explanatory variables were fat mass, lean mass and ED clinical characteristics (age, illness duration, body mass index (BMI), amenorrhoea occurrence and duration, and oral contraceptives use).

RESULTS

Forty-three studies were identified (N = 4163 women, mean age 23.4 years, min: 14.0, max: 37.4). No study with individuals with BED met the inclusion criteria. BMD in individuals with AN (total body, spine, hip, and femur), with BN (total body and spine) and with OSFED (spine) was lower than in HC. Meta-regression analyses of women with any ED (AN, BN or OSFED) (N = 2058) showed low BMI, low fat mass, low lean mass and being amenorrhoeic significantly associated with lower total body and spine BMD. In AN, only low fat mass was significantly associated with low total body BMD.

CONCLUSION

Predictors of low BMD were low BMI, low fat mass, low lean mass and amenorrhoea, but not age or illness duration. In people with EDs, body composition measurement and menstrual status, in addition to BMI, are likely to provide a more accurate assessment of individual risk to low BMD and osteoporosis.

Increased plasma asprosin levels are associated with overeating and loss of control in drug-free bulimia nervosa

PURPOSE

Abnormalities in appetite hormones have been implicated in bulimia nervosa (BN). Orexigenic hormone asprosin has been reported to be associated with food intake and weight gain, but no relevant studies have yet been reported in BN. This study investigated asprosin concentrations and their association with eating disorder symptoms in patients with BN.

METHODS

This study recruited a total of 26 BN patients and 23 healthy controls (HC). Symptom severity for eating disorders, depression, and anxiety was determined by the Eating Disorder Examination Questionnaire 6.0, Beck Depression Inventory, Version 2, and Beck Anxiety Inventory, respectively. In addition, the study employed sandwich enzyme-linked immunoassay technology to determine plasma asprosin and glucose concentrations in all participants.

RESULTS

The results revealed that plasma asprosin concentrations were significantly higher in BN patients than in HC (P = 0.037), but the difference disappeared after adjusting for the covariate BMI (F = 2.685, P = 0.108). Correlation analysis showed that asprosin concentration was positively correlated with overeating (r = 0.451, P = 0.021) and eating loss of control (r = 0.483, P = 0.012) in BN patients. Linear regression analysis indicated that an increase in asprosin concentration was associated with an increase in the times of overeating (F = 6.303, P = 0.019, R² = 0.208). Multiple linear regression showed that increases in asprosin concentration and BDI-II total score could explain the frequent eating loss of control (F = 5.766, P = 0.009, R² = 0.334).

CONCLUSIONS

The present study is the first report of plasma asprosin concentration in BN patients and found that overeating and eating loss of control increased with the increase of asprosin concentration. Additionally, asprosin level and degree of depression may explain the frequency of loss of control.

LEVEL OF EVIDENCE

Level III: Evidence obtained from case-control studies.

Leptin applications in 2015: what have we learned about leptin and obesity?

PURPOSE OF REVIEW

To summarize previous and current advancements for leptin therapeutics, we described how leptin may be useful in leptin deficient states such as lipodystrophy, for which leptin was recently approved, and how it may be useful in the future for typical obesity.

RECENT FINDINGS

The discovery of leptin in 1994 built the foundation for understanding the pathophysiology and treatment of obesity. Leptin therapy reverses morbid obesity related to congenital leptin deficiency and appears to possibly treat lipodystrophy, a finding which has led to the approval of leptin for the treatment of lipodystrophy in the USA and Japan. Typical obesity, on the other hand, is characterized by hyperleptinemia and leptin tolerance. Thus, leptin administration has proven ineffective for inducing weight loss on its own but could possibly be useful in combination with other therapies or for weight loss maintenance.

SUMMARY

Leptin is not able to treat typical obesity; however, it is effective for reversing leptin deficiency-induced obesity and is possibly useful in lipodystrophy. New mechanisms and pathways involved in leptin resistance are continuously discovered, whereas the development of new techniques and drug combinations which may improve leptin's efficacy and safety regenerate the hope for its use as an effective treatment for typical obesity.

Weight suppression in bulimia nervosa: Associations with biology and behavior

Bulimia nervosa (BN) is a serious eating disorder that can persist for years and contribute to medical complications and increased mortality, underscoring the need to better understand factors maintaining this disorder. Higher levels of weight suppression (WS) have been found to predict both the onset and maintenance of BN; however, no studies have examined mechanisms that may account for the effects of WS on BN. We hypothesized that high WS would lead to reduced leptin levels, which may increase risk of binge eating by modulating reward responses to food. The current study examined the relationship between WS, leptin levels, and the reinforcing value of food in women with BN (n = 32) and noneating disorder controls (n = 30). Participants provided information on WS, completed a fasting blood draw to obtain serum leptin, and completed a progressive ratio task to measure the reinforcing value of food. Individuals with BN had greater WS (p < .01) and reinforcing food value (p < .05) compared with controls. Additionally, higher WS was associated with both lower leptin (p < .05) and increased reinforcing value of food (p < .05). Contrary to hypotheses, BN and control participants did not differ on leptin levels, and leptin levels were not significantly associated with the reinforcing value of food. Findings support that efforts to conform to the thin ideal may alter drive to consume rewarding foods and leave women vulnerable to binge episodes. However, mechanisms through which WS contributes to food reward and binge eating remain unknown.

The role of BDNF, leptin, and catecholamines in reward learning in bulimia nervosa

BACKGROUND

A relationship between bulimia nervosa and reward-related behavior is supported by several lines of evidence. The dopaminergic dysfunctions in the processing of reward-related stimuli have been shown to be modulated by the neurotrophin brain derived neurotrophic factor (BDNF) and the hormone leptin.

METHODS

Using a randomized, double-blind, placebo-controlled, crossover design, a reward learning task was applied to study the behavior of 20 female subjects with remitted bulimia nervosa and 27 female healthy controls under placebo and catecholamine depletion with alpha-methyl-para-tyrosine (AMPT). The plasma levels of BDNF and leptin were measured twice during the placebo and the AMPT condition, immediately before and 1 hour after a standardized breakfast.

RESULTS

AMPT-induced differences in plasma BDNF levels were positively correlated with the AMPT-induced differences in reward learning in the whole sample (P=.05). Across conditions, plasma brain derived neurotrophic factor levels were higher in remitted bulimia nervosa subjects compared with controls (diagnosis effect; P=.001). Plasma BDNF and leptin levels were higher in the morning before compared with after a standardized breakfast across groups and conditions (time effect; P<.0001). The plasma leptin levels were higher under catecholamine depletion compared with placebo in the whole sample (treatment effect; P=.0004).

CONCLUSIONS

This study reports on preliminary findings that suggest a catecholamine-dependent association of plasma BDNF and reward learning in subjects with remitted bulimia nervosa and controls. A role of leptin in reward learning is not supported by this study. However, leptin levels were sensitive to a depletion of catecholamine stores in both remitted bulimia nervosa and controls.

Serum leptin and loss of control eating in children and adolescents

BACKGROUND

Both insufficiency and resistance to the actions of the adipocyte-derived hormone leptin promote hunger, increased food intake and greater body weight. Some studies suggest that adults reporting binge eating have increased serum leptin compared with those without binge eating, even after adjusting for the greater adiposity that characterizes binge eaters. Pediatric binge or loss of control (LOC) eating are prospective risk factors for excessive weight gain and may predict development of metabolic abnormalities, but whether LOC eating is associated with higher leptin among children is unknown. We therefore examined leptin and LOC eating in a pediatric cohort.

METHODS

A convenience sample of 506 lean and obese youth (7-18 years) was recruited from Washington, DC and its suburbs. Serum leptin was collected after an overnight fast. Adiposity was measured by dual-energy X-ray absorptiometry or air displacement plethysmography. LOC eating was assessed by interview methodology.

RESULTS

Leptin was strongly associated with fat mass (r=0.79, P<0.001). However, even after adjusting for adiposity and other relevant covariates, youth with LOC eating had higher serum leptin compared with those without LOC episodes (15.42±1.05 vs 12.36±1.04 ng ml(-1), P<0.001). Neither reported amount of food consumed during a recent LOC episode nor number of LOC episodes in the previous month accounted for differences in leptin (P>0.05). The relationship between LOC eating and leptin appeared to be significant for females only (P=0.002).

CONCLUSIONS

Reports of LOC eating were associated with higher fasting leptin in youth, beyond the contributions of body weight. Prospective studies are required to elucidate whether LOC eating promotes greater leptin or whether greater leptin resistance may promote LOC eating.

The role of "mixed" orexigenic and anorexigenic signals and autoantibodies reacting with appetite-regulating neuropeptides and peptides of the adipose tissue-gut-brain axis: relevance to food intake and nutritional status in patients with anorexia nervosa and bulimia nervosa

Eating disorders such as anorexia (AN) and bulimia nervosa (BN) are characterized by abnormal eating behavior. The essential aspect of AN is that the individual refuses to maintain a minimal normal body weight. The main features of BN are binge eating and inappropriate compensatory methods to prevent weight gain. The gut-brain-adipose tissue (AT) peptides and neutralizing autoantibodies play an important role in the regulation of eating behavior and growth hormone release. The mechanisms for controlling food intake involve an interplay between gut, brain, and AT. Parasympathetic, sympathetic, and serotoninergic systems are required for communication between brain satiety centre, gut, and AT. These neuronal circuits include neuropeptides ghrelin, neuropeptide Y (NPY), peptide YY (PYY), cholecystokinin (CCK), leptin, putative anorexigen obestatin, monoamines dopamine, norepinephrine (NE), serotonin, and neutralizing autoantibodies. This extensive and detailed report reviews data that demonstrate that hunger-satiety signals play an important role in the pathogenesis of eating disorders. Neuroendocrine dysregulations of the AT-gut-brain axis peptides and neutralizing autoantibodies may result in AN and BN. The circulating autoantibodies can be purified and used as pharmacological tools in AN and BN. Further research is required to investigate the orexigenic/anorexigenic synthetic analogs and monoclonal antibodies for potential treatment of eating disorders in clinical practice.

Leptin in human physiology and pathophysiology

Leptin, discovered through positional cloning 15 years ago, is an adipocyte-secreted hormone with pleiotropic effects in the physiology and pathophysiology of energy homeostasis, endocrinology, and metabolism. Studies in vitro and in animal models highlight the potential for leptin to regulate a number of physiological functions. Available evidence from human studies indicates that leptin has a mainly permissive role, with leptin administration being effective in states of leptin deficiency, less effective in states of leptin adequacy, and largely ineffective in states of leptin excess. Results from interventional studies in humans demonstrate that leptin administration in subjects with congenital complete leptin deficiency or subjects with partial leptin deficiency (subjects with lipoatrophy, congenital or related to HIV infection, and women with hypothalamic amenorrhea) reverses the energy homeostasis and neuroendocrine and metabolic abnormalities associated with these conditions. More specifically, in women with hypothalamic amenorrhea, leptin helps restore abnormalities in hypothalamic-pituitary-peripheral axes including the gonadal, thyroid, growth hormone, and to a lesser extent adrenal axes. Furthermore, leptin results in resumption of menses in the majority of these subjects and, in the long term, may increase bone mineral content and density, especially at the lumbar spine. In patients with congenital or HIV-related lipoatrophy, leptin treatment is also associated with improvements in insulin sensitivity and lipid profile, concomitant with reduced visceral and ectopic fat deposition. In contrast, leptin's effects are largely absent in the obese hyperleptinemic state, probably due to leptin resistance or tolerance. Hence, another emerging area of research pertains to the discovery and/or usefulness of leptin sensitizers. Results from ongoing studies are expected to further increase our understanding of the role of leptin and the potential clinical applications of leptin or its analogs in human therapeutics.

Leptin is an effective treatment for hypothalamic amenorrhea

Hypothalamic amenorrhea (HA) is associated with dysfunction of the hypothalamic-pituitary-peripheral endocrine axes, leading to infertility and bone loss, and usually is caused by chronic energy deficiency secondary to strenuous exercise and/or decreased food intake. Energy deficiency also leads to hypoleptinemia, which has been proposed, on the basis of observational studies as well as an open-label study, to mediate the neuroendocrine abnormalities associated with this condition. To prove definitively a causal role of leptin in the pathogenesis of HA, we performed a randomized, double-blinded, placebo-controlled trial of human recombinant leptin (metreleptin) in replacement doses over 36 wk in women with HA. We assessed its effects on reproductive outcomes, neuroendocrine function, and bone metabolism. Leptin replacement resulted in recovery of menstruation and corrected the abnormalities in the gonadal, thyroid, growth hormone, and adrenal axes. We also demonstrated changes in markers of bone metabolism suggestive of bone formation, but no changes in bone mineral density were detected over the short duration of this study. If these data are confirmed, metreleptin administration in replacement doses to normalize circulating leptin levels may prove to be a safe and effective therapy for women with HA.

Association of maternal short sleep duration with adiposity and cardiometabolic status at 3 years postpartum

The purpose of this study was to examine the association of short sleep duration among women in the first year postpartum with adiposity and cardiometabolic status at 3 years postpartum. We studied 586 women in Project Viva, a prospective cohort. At 6 months and 1 year postpartum, women reported the number of hours they slept in a 24-h period, from which we calculated a weighted average of daily sleep. We used multivariable regression analyses to predict the independent effects of short sleep duration (≤5 h/day vs. >5 h/day) on adiposity, glucose metabolism, lipid metabolism, and adipokines at 3 years postpartum. Women's mean (s.d.) hours of daily sleep in the first year postpartum was 6.7 (0.97) h. After adjusting for age, race/ethnicity, education, parity, prepregnancy BMI, and excessive gestational weight gain, we found that postpartum sleep ≤5 h/day was associated with higher postpartum weight retention (β 1.50 kg; 95% confidence interval (CI): 0.02, 2.86), higher subscapular + triceps skinfold thickness (β 3.94 mm; 95% CI: 1.27, 6.60) and higher waist circumference (β 3.10 cm; 95% CI: 1.25, 4.94) at 3 years postpartum. We did not observe associations of short sleep duration with measures of cardiometabolic status at 3 years postpartum. In conclusion, short sleep duration in the first year postpartum is associated with higher adiposity at 3 years postpartum.

Psychobiology of purging disorder: reduction in circulating leptin levels in purging disorder in comparison with controls

OBJECTIVE

Purging disorder (PD), a recently recognized eating disorder syndrome, is differentiated from bulimia nervosa (BN) based on the absence of objectively large binge episodes. BN has been associated with low serum leptin levels. This study examined whether PD is also characterized by low serum leptin.

METHOD

Participants included women with PD (n = 20) or BN (n = 37), and non-eating disorder controls (n = 33). Blood samples for measurement of leptin and total ghrelin were obtained after overnight fast.

RESULTS

In comparison with control values, leptin levels were significantly decreased in PD (p < .01), as well as in BN (p < .02). Plasma ghrelin levels did not differ significantly across groups.

DISCUSSION

These results provide the first evidence that PD is associated with alteration in a neurobiological pathway influencing eating patterns and body weight. Further research is needed to assess whether low leptin levels in PD and BN are associated with restrained eating and weight suppression.

Leptin in human physiology and therapeutics

Leptin regulates energy homeostasis and reproductive, neuroendocrine, immune, and metabolic functions. In this review, we describe the role of leptin in human physiology and review evidence from recent "proof of concept" clinical trials using recombinant human leptin in subjects with congenital leptin deficiency, hypoleptinemia associated with energy-deficient states, and hyperleptinemia associated with garden-variety obesity. Since most obese individuals are largely leptin-tolerant or -resistant, therapeutic uses of leptin are currently limited to patients with complete or partial leptin deficiency, including hypothalamic amenorrhea and lipoatrophy. Leptin administration in these energy-deficient states may help restore associated neuroendocrine, metabolic, and immune function and bone metabolism. Leptin treatment is currently available for individuals with congenital leptin deficiency and congenital lipoatrophy. The long-term efficacy and safety of leptin treatment in hypothalamic amenorrhea and acquired lipoatrophy are currently under investigation. Whether combination therapy with leptin and potential leptin sensitizers will prove effective in the treatment of garden-variety obesity and whether leptin may have a role in weight loss maintenance is being greatly anticipated.

Walnut consumption increases satiation but has no effect on insulin resistance or the metabolic profile over a 4-day period

Obesity and diabetes have been associated with increased consumption of highly processed foods, and reduced consumption of whole grains and nuts. It has been proposed, mainly on the basis of observational studies, that nuts may provide superior satiation, may lead to reduced calorie consumption, and may decrease the risk of type 2 diabetes; but evidence from randomized, interventional studies is lacking. A total of 20 men and women with the metabolic syndrome participated in a randomized, double-blind, crossover study of walnut consumption. Subjects had two 4-day admissions to the clinical research center where they were fed an isocaloric diet. In addition, they consumed shakes for breakfast containing either walnuts or placebo (shakes were standardized for calories, carbohydrate, and fat content). Appetite, insulin resistance, and metabolic parameters were measured. We found an increased level of satiety (overall P value = 0.0079) and sense of fullness (P = 0.05) in prelunch questionnaires following the walnut breakfast as compared to the placebo breakfast, with the walnut effect achieving significance on day 3 and 4 (P = 0.02 and P = 0.03). We did not find any change in resting energy expenditure, hormones known to mediate satiety, or insulin resistance when comparing the walnut vs. placebo diet. Walnut consumption over 4 days increased satiety by day 3. Long-term studies are needed to confirm the physiologic role of walnuts, the duration of time needed for these effects to occur, and to elucidate the underlying mechanisms.

Racial/ethnic differences in early-life risk factors for childhood obesity

OBJECTIVE

By the preschool years, racial/ethnic disparities in obesity prevalence are already present. The objective of this study was to examine racial/ethnic differences in early-life risk factors for childhood obesity.

METHODS

A total of 1343 white, 355 black, and 128 Hispanic mother-child pairs were studied in a prospective study. Mother's reported child's race/ethnicity. The main outcome measures were risk factors from the prenatal period through 4 years old that are known to be associated with child obesity.

RESULTS

In multivariable models, compared with their white counterparts, black and Hispanic children exhibited a range of risk factors related to child obesity. In pregnancy, these included higher rates of maternal depression (odds ratio [OR]: 1.55 for black, 1.89 for Hispanic); in infancy more rapid weight gain (OR: 2.01 for black, 1.75 for Hispanic), more likely to introduce solid foods before 4 months of age (OR: 1.91 for black, 2.04 for Hispanic), and higher rates of maternal restrictive feeding practices (OR: 2.59 for black, 3.35 for Hispanic); and after 2 years old, more televisions in their bedrooms (OR: 7.65 for black, 7.99 for Hispanic), higher intake of sugar-sweetened beverages (OR: 4.11 for black, 2.48 for Hispanic), and higher intake of fast food (OR: 1.65 for black, 3.14 for Hispanic). Black and Hispanic children also had lower rates of exclusive breastfeeding and were less likely to sleep at least 12 hours/day in infancy.

CONCLUSIONS

Racial/ethnic differences in risk factors for obesity exist prenatally and in early childhood. Racial/ethnic disparities in childhood obesity may be determined by factors that operate at the earliest stages of life.

Narrative review: the role of leptin in human physiology: emerging clinical applications

Leptin is a hormone secreted by adipose tissue in direct proportion to amount of body fat. The circulating leptin levels serve as a gauge of energy stores, thereby directing the regulation of energy homeostasis, neuroendocrine function, and metabolism. Persons with congenital deficiency are obese, and treatment with leptin results in dramatic weight loss through decreased food intake and possible increased energy expenditure. However, most obese persons are resistant to the weight-reducing effects of leptin. Recent studies suggest that leptin is physiologically more important as an indicator of energy deficiency, rather than energy excess, and may mediate adaptation by driving increased food intake and directing neuroendocrine function to converse energy, such as inducing hypothalamic hypogonadism to prevent fertilization. Current studies investigate the role of leptin in weight-loss management because persons who have recently lost weight have relative leptin deficiency that may drive them to regain weight. Leptin deficiency is also evident in patients with diet- or exercise-induced hypothalamic amenorrhea and lipoatrophy. Replacement of leptin in physiologic doses restores ovulatory menstruation in women with hypothalamic amenorrhea and improves metabolic dysfunction in patients with lipoatrophy, including lipoatrophy associated with HIV or highly active antiretroviral therapy. The applications of leptin continue to grow and will hopefully soon be used therapeutically.

Cord blood leptin and adiponectin as predictors of adiposity in children at 3 years of age: a prospective cohort study

OBJECTIVES

Leptin and adiponectin are adipocyte-secreted hormones that regulate energy homeostasis and metabolism. Because their roles in the neonatal period and in early childhood are poorly understood, we aimed in this prospective cohort study to determine the extent to which umbilical cord blood leptin and adiponectin concentrations predict measures of adiposity and growth at 3 years of age.

PATIENTS AND METHODS

We studied 588 children participating in the prospective prebirth cohort study Project Viva. We examined associations of cord blood leptin and adiponectin levels with weight changes during the first 6 months of life, 3-year circulating leptin and adiponectin concentrations, and the following adiposity-related outcomes at 3 years of age: BMI z score, height-for-age z score, and sums of triceps and subscapular skinfold thicknesses to represent overall adiposity, as well as subscapular/triceps skinfold ratio to represent central adiposity.

RESULTS

Cord blood leptin and adiponectin were each directly associated with the duration of gestation and birth weight for gestational age z scores. Cord blood leptin levels were negatively associated with change in weight-for-length, weight-for-age, and length-for-age z scores between birth and 6 months of age. Similarly, cord blood adiponectin was negatively associated with change in weight-for-length and weight-for-age z scores. After adjusting for several maternal and child factors related to obesity, each 10 ng/mL increment of cord blood leptin was associated with a reduction in BMI z score and higher leptin levels at 3 years but not with skinfold thicknesses. Each 10 microg/mL increment of cord blood adiponectin was positively associated with a higher subscapular skinfold thickness/triceps skinfold thickness ratio at 3 years.

CONCLUSIONS

Lower cord blood leptin levels are associated with smaller size at birth but more pronounced weight gain in the first 6 months of life and higher BMI at 3 years of age. Cord blood adiponectin levels are also directly associated with birth weight for gestational age, inversely associated with weight gain in the first 6 months of life, and predict an increase in central adiposity at age 3 years.

Leptin and its associations with measures of psychopathology in patients with anorexia nervosa

Apart from energy homeostasis leptin has been shown to be involved in a number of neuronal networks. The aim of this study was to investigate how the residual variance of leptin levels, after controlling for BMI, is linked to eating-disorder-specific psychopathology and sexual desire in patients with anorexia nervosa (AN) compared to healthy controls. The sample included 57 subjects with acute AN and 77 healthy controls. Psychopathology was determined by EDI-2 and SCL-90-R and sexual problems were rated according to the Structured Interview of Anorexia Nervosa and Bulimic Syndromes (SIAB-EX). Plasma leptin was assessed by ELISA. Patients with a high drive for thinness had lower leptin levels at a given BMI and low leptin levels were associated with sexual problems, i.e. the absence of sexual desire and intimate relationships. Our results are in accordance with recent animal experiments linking low leptin levels with decreased sexual interest irrespective of body weight.

Leptin and puberty: a review

Over the last few years, many studies have focused on leptin, the product of the LEP (ob) gene, searching for a possible link between energy balance and reproduction. The involvement of this peptide in the regulation of the hypothalamo-pituitary-adrenal, gonadal, thyroid and somatotroph axes suggests that leptin might play a pivotal role in coordinating the activity of these axes and their relationship with the body's energy balance. The effects of leptin on hypothalamic, pituitary and peripheral hormone levels, as well as the presence of the leptin receptor in a variety of tissues, suggest both an endocrine and a paracrine mode of action. Particular attention was paid to the effect of leptin on the gonadal axis as infertility, a characteristic feature of both the leptin deficient ob/ob mice and the leptin receptor mutant db/db mice, could be corrected in ob/ob mice by leptin administration. Considerable leptin level changes were observed during puberty both in animal and human studies. A matter of controversy is the precise role of leptin in the onset of puberty: is leptin the signal that initiates puberty and the accompanying hormonal changes, or has leptin only a permissive but key role for the onset of puberty, as likely seems to be the case for the maintenance of a functional gonadotroph axis? On current evidence, a mainly permissive role seems most probable.