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.

Good syndrome (GS) is a rare association of thymoma and immunodeficiency first described more than 50 years ago. However, this syndrome still remains a mystery to clinicians. We systematically reviewed all the clinical, laboratory and immunologic findings from 152 patients with Good syndrome. The syndrome has a worldwide distribution and approximately half of the cases (47%) have been described in Europe. The diagnosis of thymoma preceded the diagnosis of hypogammaglobulinemia, infection, or diarrhea in 42% of patients whereas in 38% of patients the diagnoses were made almost simultaneously within 2 months of each other. We found significant mortality in patients with this syndrome (44.5%). Astute clinical acumen and increased awareness about the clinical and immunological profile of this syndrome may increase early recognition of this syndrome and prevent mortality. Further studies are needed to elucidate this clinical entity.

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 µg/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.