Evaluating the patients with thalassemia major for long-term endocrinological complications after bone marrow transplantation.

The aim of this study was to evaluate the endocrinological complications of the patients with thalassemia major (TM) who underwent bone marrow transplantation (BMT) and followed-up more than two years in our center, prospectively. "BMT group" consisted of 41 patients with TM. The mean age was 12.4 ± 5.4 years and transplantation age was mean 7.5 ± 4.9 years. Post-BMT follow-up lasted from 24 to 122 months (mean 65.07 months). Also, 32 TM patients with similar age group and same history of transfusion and chelation therapy were recruited for the study as "control (C) group". The weight SDS score after transplantation was found better than before transplantation (p = 0.010). There was a negative correlation between height SDS and BMT age (p = 0.008). The height SDS scores were better in patients whose BMT age was under seven years old compared to those older than seven years old (p = 0.02). Z-scores of femur neck and L2-4 vertebrae DEXA were decreased (p = 0.032, p = 0.0001) and incidence of insulin resistance increased (p = 0.01) in patients with increased BMT age. The risk of gonadal insufficiency was significantly lower in the patients who underwent BMT <7 years of age (p = 0.009). There was no statistically significant relationship between BMT age and complications such as hypothyroidism, hypoparathyroidism, and adrenal insufficiency. The patients with TM should be evaluated for transplantation in early stage of the disease, especially before the age of seven years. Because the BMT cannot correct the endocrinological complications of TM completely, the patients should be followed up regularly after the transplantation.

Mixed gonadal dysgenesis in a patient with de novo tas(Y;19)(p11.3;q13.4) and 45,X mosaicism.

We report a patient with a de novo telomeric association between chromosomes 19 and Y in conjunction with mixed gonadal dysgenesis. The patient was first admitted to the clinic because of abnormal external genitalia. Laparoscopic evaluation revealed (1) a rudimentary uterus, one fallopian tube, and a small gonad resembling an ovary on the right side, and (2) an immature fallopian tube, a vas deferens, and a gonad resembling a testis on the left side. Conventional cytogenetic analysis performed on cultivated peripheral blood cells, and tissue obtained from the phallus and a gonadal structure which resembled a testis revealed two different cell lines with the 46,X,tas (Y;19)(p11.3;q13.4) and 45,X karyotype. Y chromosome microdeletion analysis showed that the patient did not have any genomic deletions in the AZFa, b, c, or SRY regions on the long arm of the Y chromosome. This is the first report of a patient with mixed gonadal dysgenesis that is accompanied by a telomeric association between chromosomes 19 and Y with 45,X mosaicism.

A novel DAX-1 mutation presented with precocious puberty and hypogonadotropic hypogonadism in different members of a large pedigree.

Patients with DAX-1 gene mutations on chromosome Xp21 usually present with adrenal hypoplasia congenita and hypogonadotropic hypogonadism. Yet, neither correlation between the type of mutation and the age of onset of the disease nor mechanism of the mutation on puberty is fully understood. Here, we report a novel non-sense p.Gln208X mutation in the amino terminal domain of the DAX-1 gene observed in a large family with three boys presenting with adrenal manifestations at different ages. Furthermore, two boys developed spontaneous puberty that failed to progress at similar ages, whereas the other boy developed precocious puberty at 10 month of age. The unique structure of the DAX-1 gene may explain this phenotypic variability. However, more studies are needed to understand the role of the DAX-1 gene on development of the adrenal gland and hypothalamus-pituitary-gonadal axis.

Clinical and genetic analysis of patients with vitamin D-dependent rickets type 1A.

CONTEXT: Vitamin D-dependent rickets type 1A (VDDR-IA, OMIM 264700) is a rare autosomal recessive disorder and is caused by mutations in the CYP27B1 gene. OBJECTIVES: We aim to investigate CYP27B1 mutation in seven patients from four separate families and characterize the genotype-phenotype correlation. METHODS: The entire coding region of the CYP27B1 gene was sequenced, and genotype-phenotype correlation among patients was assessed. RESULTS: Sequencing analysis identified biallelic CYP27B1 mutations in all patients and monoallelic mutations in their parents. One patient from the first family was compound heterozygous for c.1166G>A (p.Arg389His) and a novel nonsense mutation c.1079 C>A (p.Ser360*). Two patients from the second family were homozygous for a novel splice donor site mutation in intron 1 (c.195 + 2 T>G), causing partial retention of the intron and a shift in the reading frame. Both novel mutations lead to the complete loss of vitamin D1α-hydroxylase activity. Four patients from families 3 and 4 were homozygous for a previously reported duplication mutation in exon 8 (1319-1325dupCCCACCC, Phe443Profs*24). Interestingly, one patient who was presented with severe hypocalcaemia and seizures at 4 months of age as a result of Phe443Profs*24 has improved spontaneously since 11 years of age and does not need regular treatment. Her laboratory tests showed normal serum calcium and 1,25(OH)(2) D after refusing to take medication for 12 months. CONCLUSIONS: There is a good genotype-phenotype correlation in VDDR-IA. However, some patients may recover from the loss of CYP27B1 function, probably due to 1α-hydroxylase activity exerted by a non-CYP27B1 enzyme.

Intrathyroidal ectopic thymic tissue may mimic thyroid cancer: a case report.

Ectopic intrathyroidal thymus tissue that may be present as a thyroid nodule is rarely reported. We present a case of a 4-year-old boy with a solitary thyroid nodule. Real-time thyroid ultrasound showed a calcified nodule in the right lobe. Complete blood count, serum calcitonin, and thyroglobulin concentration were normal and antithyroid antibodies were negative. Fine-needle aspiration (FNA) biopsy was revealed as inadequate for cytological examination. During his follow-up, nodular enlargement was found, and the patient was subjected to surgical total excision of the right lobe of the thyroid gland. Pathological examination showed an ectopic intrathyroidal thymus tissue. In childhood, ectopic intrathyroidal thymus tissue can present as an enlarging microcalcified thyroid nodule that may mimic thyroid cancer and may grow during follow-up.

Variability in the age at diagnosis of diabetes in two unrelated patients with a homozygous glucokinase gene mutation.

Homozygous mutations in the glucokinase gene (GCK) result in a complete deficiency of the GCK enzyme, which leads to permanent neonatal diabetes mellitus. Whilst there has been one report of a patient (with a homozygous p.T168A) who was diagnosed with diabetes at the age of 2 months, all other cases were diagnosed with diabetes within the first 2 weeks of life. We now report a second unrelated patient with the same p.T168A GCK mutation who was diagnosed with diabetes at the age of 9 months. We conclude that the specific GCK mutation, as yet unidentified genetic modifiers, and/or environmental factors might have different effects on pancreatic beta-cell functions, causing variability in the age at diagnosis of diabetes.

Severe rhabdomyolysis and acute renal failure in an adolescent with hypothyroidism.

Hypothyroidism has been reported rarely as the cause of rhabdomyolysis in adults and children. We present here a non-compliant adolescent with a diagnosis of hypothyroidism who developed rhabdomyolysis and acute renal failure with no additional predisposing factor. A 13-year-old girl with a previous history of hypothyroidism due to thyroid hypoplasia presented with generalized myalgia, malaise, vomiting, and oliguria lasting for three days. Neurological examination revealed bilateral marked weakness and tenderness of muscles of both lower and upper extremities. Urine had bloody appearance and urine analysis showed blood reaction with dipstick test, but there were no erythrocytes on microscopic examination. Serum creatine phosphokinase and myoglobin levels were elevated. Thyroid stimulating hormone (TSH) levels were high, and free thyroxine (T4) and triiodothyronine (T3) levels were low, compatible with uncontrolled hypothyroidism. Renal function tests showed acute renal failure. Other causes of rhabdomyolysis such as muscular trauma, drugs, toxins, infections, vigorous exercise, and electrolyte abnormalities were excluded. Hemodialysis was administered for 24 sessions. After L-thyroxine therapy, thyroid function tests normalized, muscle strength improved, serum muscle enzyme levels returned to normal levels, and renal function tests recovered. One must be aware that rhabdomyolysis may develop in a non-compliant patient with hypothyroidism.

The Results of 16 Years of Iodization: Assessment of Iodine Deficiency Among School-age Children in Antalya, Turkey

Objective: Iodine deficiency (ID) continues to be a problem around the world. This study investigated the prevalence of ID and goiter among school-age children in the city center of Antalya, Turkey. The aim was to investigate the effect of an iodization program, which had been running for sixteen years, on nutritional iodine status in this population. Methods: A total of 1,594 school children, aged 6-14 years, were included in this cross-sectional study. ID was evaluated based on median [interquartile range (IQR)] urine iodine/creatine (UI/Cr) (µg/g) ratio and median (IQR) UI concentrations (UIC) (µg/L). UICs were measured using the Sandell-Kolthoff method. Goiter was determined by palpation and staged according to World Health Organization classification. Results: Median (IQR) UIC was found to be 174.69 (119.17-242.83) µg/L, and UIC was found to be lower than 50 µg/L in 6.5% of the population. The median UI/Cr ratio increased from 62.3 to 163.3 µg/g and goiter rates had decreased from 34% to 0.3% over the 16 years of the program. However, 19% were still classified as ID (mild, moderate or severe) and, furthermore, 11.5% were classified as excessive iodine intake. Conclusion: Comparison of two cross-sectional studies, carried out 16-years apart, showed that Antalya is no longer an ID region. However, surveillance should be continued and the percentage of ID and iodine excess individuals in the population should be monitored to avoid emerging problems.

Final diagnosis in children with subclinical hypothyroidism and mutation analysis of the thyroid peroxidase gene (TPO).

AIM: To determine the final diagnosis of patients with subclinical hypothyroidism (SCH), and to perform mutation screening of the thyroid peroxidase gene (TPO). METHODS: Infants with SCH without an identified etiology were included in the study. Patients with thyroid dysgenesis were excluded. Children > or = 2 years of age, and still on L-thyroxine (LT4) treatment underwent a diagnostic algorithm. After LT4 was discontinued for 4 weeks, thyroid function tests (TFT) were obtained. A perchlorate discharge test (PDT) was performed in patients with normal thyroid ultrasound but abnormal TFT. Sequence analysis of TPO was studied in all children who underwent a PDT. RESULTS: Forty-eight patients (23 males and 25 females) completed the trial. Among these children, 19 (39.5%) had transient SCH, and 29 (60.5%) had permanent SCH. Among patients with permanent SCH, 19 had thyroid hypoplasia, six had partial iodide organification defect with positive PDT, and four had other dyshormonogenesis with negative PDT. Mean LT4 dose before the medication ceased was 1.2 +/- 0.5 microg/kg/day in transient cases, and 1.7 +/- 0.4 in those with permanent SCH (p < 0.05). No TPO mutation was detected. However, in five patients, seven different previously known TPO polymorphisms were detected: c.102C > G, L4L; > A, A576A; c.2088C > T, D666D; c.2263A > C, T725P; c.2630 T >C, V847A. CONCLUSIONS: LT4 treatment should be stopped after the age of 2 years in infants with SCH without a definite pathology of the thyroid gland to exclude cases with transient hypothyroidism. Additionally, we should consider particularly thyroid gland hypoplasia, and also partial defects in iodide organification in infants with SCH.

Remarkable Increase in the Prevalence of Overweight and Obesity Among School Age Children in Antalya, Turkey, Between 2003 and 2015

Objective: Childhood obesity (OB) is an acknowledged global problem with increasing prevalence reported around the world. We conducted this study with the aim of determining the local trend in OB and overweight (OW) prevalence in the last decade and to observe the alteration of OB and OW prevalence by age group. An additional aim was to construct new age- and gender-specific body mass index (BMI) reference percentile charts for Turkish children living in the city center of Antalya. Methods: This cross-sectional study included 1687 school aged children. International Obesity Task Force guidelines were used to determine the OB and OW prevalence. OW was defined as a BMI between 85th and 95th percentile, and OB >95th percentile. The data were compared with a previous study carried out in the same region in 2003. The least mean square method was used to construct the BMI reference percentile charts. Results: The prevalence rates for OB and OW were 9.8% and 23.2%, respectively, with a combined OW/OB rate of 33%. OB prevalence was higher in boys than girls (p<0.05). The prevalence of combined OW/OB was highest at age 9-10 years. The prevalence of OB has increased 2.9 times during twelve years in this location. Conclusion: Comparing the current findings with rates of OW and OB in the previous decade, childhood OB in Antalya has reached alarming levels. Urgent measures integrated into the national education system should be taken to prevent OB. In addition more surveillance studies should be planned to show the future trend of OB prevalence nationally.

Permanent neonatal diabetes mellitus caused by a novel homozygous (T168A) glucokinase (GCK) mutation: initial response to oral sulphonylurea therapy.

OBJECTIVE: To evaluate the clinical response to sulphonylurea treatment in a child with a homozygous T168A GCK (glucokinase) mutation, causing permanent neonatal diabetes mellitus (PNDM). STUDY DESIGN: Oral glibenclamide was given for 3 months. Pancreatic beta cell function was assessed by a glucagon stimulation test. Mutant and wild-type (WT) GCK were characterized. RESULTS: Sulphonylurea treatment resulted in a 12-fold increase in basal and stimulated C-peptide levels. HbA1c levels were reduced from 9.4% to 8.1% on a reduced insulin dose (0.85 to 0.60 U/kg/day). Mutant T168A-GST-GCK showed reduced kinetic activity (0.02 fold) compared to WT. CONCLUSIONS: Sulphonylureas can close the adenosine triphosphate (ATP)-sensitive potassium channel and elicit insulin secretion, but the ATP generated from metabolism is insufficient to fully restore insulin secretory capacity. Nonetheless, sulphonylurea treatment should be tried in patients with GCK-PNDM, particularly those with mutations resulting in less severe kinetic defects, in whom improved glycemic control may be obtained with lower doses of insulin.

Urinary phthalate metabolite concentrations in girls with premature thelarche.

In girls, breast development before eight years of age is called "premature thelarche (PT)". There are few studies in literature that show the interaction between PT and phthalate exposure. The aim of this study was to determine the urinary levels of di-(2-ethylhexyl) phthalate (DEHP) metabolites and other phthalate metabolites in girls with PT. PT group consisted of 29 newly diagnosed subjects. Control group comprised of healthy age-matched girls (n = 25). Urinary phthalate metabolite concentrations were measured by liquid chromatography/tandem mass spectroscopy (LC-MS/MS). The urinary concentrations of mono-(2-ethyl-hexyl)phthalate (MEHP) in the PT group (33.96 ±â€¯6.88 µg/g creatinine) were found to be significantly higher compared to control group (11.54 ±â€¯1.39 µg/g creatinine, p = 0.002). In PT group, %MEHP was also markedly higher vs. control (17.84 ±â€¯3.31 vs. 6.44 ±â€¯1.13, p = 0.001). Our results suggest that DEHP is more efficiently converted to MEHP in girls with PT, the importance of which needs to be further elucidated.

Response to growth hormone treatment in very young patients with growth hormone deficiencies and mini-puberty.

BACKGROUND: The aim of the study was to assess the response to growth hormone (GH) treatment in very young patients with GH deficiency (GHD) through a national, multi-center study. Possible factors affecting growth response were assessed (especially mini-puberty). METHODS: Medical reports of GHD patients in whom treatment was initiated between 0 and 3 years of age were retrospectively evaluated. RESULTS: The cohort numbered 67. The diagnosis age was 12.4±8.6 months, peak GH stimulation test response (at diagnosis) as 1.0±1.4 ng/mL. The first and second years length gain was 15.0±4.3 and 10.4±3.4 cm. Weight gain had the largest effect on first year growth response; whereas weight gain and GH dose were both important factors affecting second year growth response. In the multiple pituitary hormone deficiency (MPHD) group (n=50), first year GH response was significantly greater than in the isolated GH deficiency (IGHD) group (n=17) (p=0.030). In addition first year growth response of infants starting GH between 0 and 12 months of age (n=24) was significantly greater than those who started treatment between 12 and 36 months of age (n=43) (p<0.001). These differences were not seen in the second year. Δ Length/height standard deviation score (SDS), Δ body weight SDS, length/height SDS, weight SDS in MPHD without hypogonadism for the first year of the GH treatment were found as significantly better than MPHD with hypogonadism. CONCLUSIONS: Early onsets of GH treatment, good weight gain in the first year of the treatment and good weight gain-GH dose in the second year of the treatment are the factors that have the greatest effect on length gain in early onset GHD. The presence of the sex steroid hormones during minipubertal period influence growth pattern positively under GH treatment (closer to the normal percentage according to age and gender).

Type 1 diabetes-related epidemiological, clinical and laboratory findings. An evaluation with special regard to autoimmunity in children.

OBJECTIVE: To evaluate our data related with epidemiologic features, clinical presentation, and laboratory findings in children with type 1 diabetes mellitus (DM1) and to compare specific characteristics of immune-mediated subtype (DM 1A) with idiopathic one (DM 1B). METHODS: We classified 115 children with DM1 according to the presence (DM 1A, n=77) or absence (DM 1B, n=38) of diabetes-related autoantibodies in Akdeniz University Hospital, Turkey from January 2000 to December 2005. RESULTS: A total of 43 patients (37%) in the whole group, had onset of DM1 during the winter months and the lowest frequency occurred in summer (p<0.005). The duration of breast-feeding, introduction time of cow's milk, and seasonal distribution of birth-month or onset of disease did not significantly differ in both groups. When compared with patients who had no documented honeymoon period, the patients who had a documented honeymoon period had lower HbA1c levels (p<0.01) at the onset. A large percentage of patients with DM 1A were positive for glutamic acid decarboxylase antibody (GAD65). CONCLUSION: There was no significant difference between patients with DM 1A and DM 1B with respect to epidemiologic features, and clinical presentation suggested that these factors do not play a major role either in creating a disease-initiating effect or in the development of islet autoimmunity. However, determination of GAD65 with HbA1c levels at the onset of the disease may ensure some useful information regarding clinical course.

Clinical and Molecular Genetic Analysis in Three Children with Wolfram Syndrome: A Novel WFS1 Mutation (c.2534T>A).

Wolfram syndrome (WS) is an autosomal recessive disorder caused by mutations in WFS1 gene. The clinical features include diabetes insipidus, diabetes mellitus (DM), optic atrophy, deafness, and other variable clinical manifestations. In this paper, we present the clinical and genetic characteristics of 3 WS patients from 3 unrelated Turkish families. Clinical characteristics of the patients and the age of onset of symptoms were quite different in each pedigree. The first two cases developed all symptoms of the disease in their first decade of life. The heterozygous father of case 2 was symptomatic with bilateral deafness. The first ocular finding of one patient (patient 3) was bilateral cataract which was accompanying DM as a first feature of the syndrome. In this patient's family, there were two members with features suggestive of WS. Previously known homozygous mutations, c.460+1G>A in intron 4 and c.1885C>T in exon 8, were identified in these cases. A novel homozygous c.2534T>A mutation was also detected in the exon 8 of WFS1 gene. Because of the rarity and heterogeneity of WS, detection of specific and nonspecific clinical signs including ocular findings and family history in non-autoimmune, insulinopenic diabetes cases should lead to a tentative diagnosis of WS. Genetic testing is required to confirm the diagnosis.

Leptin levels and body composition in children and adolescents with type 1 diabetes.

The purpose of this study was to determine the relationship between serum leptin levels and body composition and to evaluate the variables related to disease in children and adolescents with type 1 diabetes. We studied 49 diabetic patients aged 6-16 years (age: 11.2+/-2.9 years, M/F: 26/23), and 37 healthy controls. Body composition was determined by dual-energy X-ray absorptiometry. Serum leptin, glycated hemoglobin (HbA1c), free thyroxin, thyrotropin, testosterone and estradiol levels were measured in patients and controls. We did not observe significant difference in serum leptin levels between patients and controls. Girls had significantly higher serum leptin levels than boys in both patient and control groups. Serum leptin levels did not correlate significantly with HbA1c, disease duration or daily insulin dose but, correlated positively with body mass index (BMI) and fat mass (FM) in patients as in controls. Body composition in diabetic girls and boys was similar with respective controls. When analyzed by pubertal stage, BMI, lean body mass (LBM), FM, and total bone mineral density (BMD) were significantly higher in pubertal girls with type 1 diabetes compared to prepubertal ones. In pubertal boys with type 1 diabetes, LBM and FM were significantly higher than prepubertal ones. The results of the present study showed that neither serum leptin levels nor body composition was significantly altered in children and adolescents with type 1 diabetes managed with intensive insulin therapy.

Comparison of breakfast and bedtime administration of insulin glargine in children and adolescents with Type 1 diabetes.

OBJECTIVE: The purpose of this study was to evaluate the effect of administration time of insulin glargine (IG) on glycemic control in children and adolescents with Type 1 diabetes. MATERIALS AND METHODS: A total of 31 children and adolescents (15 F and 16 M) with Type 1 diabetes on intensive therapy (bedtime NPH and premeal insulin aspart) were randomized to receive once-daily IG either at breakfast (breakfast group, n=15) or bedtime (bedtime group, n=16) while continuing insulin aspart premeals for 6 months. Blood glucose levels were measured fasting, preprandially and bedtime. Total daily insulin dose (TDD), body mass index (BMI), glycosylated hemoglobin (HbA(1c)), and frequency of hypoglycemia in the preceding 3 months were assessed at recruitment, third month and sixth month. RESULTS: The dose of IG, TDD, and fasting blood glucose levels were similar in both groups during the study period. The only significant difference in blood glucose levels between breakfast and bedtime groups was found for dinnertime at 6 months (135+/-26mg/dl versus 161+/-33mg/dl, respectively, p=0.035). In the breakfast group, the mean HbA(1c) level was significantly lower than that of baseline at month 6 (9.4+/-2.5% versus 8.0+/-0.9%, respectively, p=0.022), whereas there was no significant change in the bedtime group (9.2+/-2.1% versus 8.9+/-2.2%, respectively). The frequency of hypoglycemia was lower with IG than NPH (2.7+/-2.8/6 months versus 6.4+/-6.7/6 months, respectively, p=0.008). CONCLUSIONS: Once-daily IG at breakfast in children and adolescents with Type 1 diabetes on intensive therapy is more efficacious than bedtime administration to improve metabolic control. Also, the number of hypoglycaemic events decreased with both breakfast and bedtime administrations of IG.

An unusual case of chromosome 22q11 deletion syndrome with psychiatric disorder, hypoparathyroidism and precocious puberty.

Deletions of chromosome 22q11 cause a wide range of phenotypes; even affected members from the same family may present with different phenotype. We present an 11-3/12 year-old boy who has 22q11 deletion in a hitherto unreported combination with psychiatric disorder, hypoparathyroidism and precocious puberty. Whether precocious puberty is a clue for chromosome 22q11 deletion syndrome is also discussed.

Bone mineral density and alterations of bone metabolism in children and adolescents with type 1 diabetes mellitus.

OBJECTIVES: To analysis bone mineral density (BMD) and bone turnover markers in children and adolescents with type 1 diabetes mellitus (DM1) and to establish possible correlations with duration of the disease and degree of metabolic control. PATIENTS AND METHODS: Fifty-eight (26 prepubertal, 32 pubertal) children (29 boys) with DM1 (age: 11.7 +/- 3.1 years) and 44 (20 prepubertal, 24 pubertal) healthy children (21 boys) as controls (age: 10.8 +/- 3.2 years) were included in the study. BMD was measured by dual energy X-ray absorptiometry (DEXA). Scans of the lumbar spine (LS2-4) and femoral neck (FN) were carried out. Serum levels of osteocalcin, amino-terminal propeptide of type I procollagen (PINP), and alkaline phosphatase, as markers of bone formation, and urinary calcium/creatinine (Ca/Cr) ratio and levels of N-telopeptide (Ntx), as markers of bone resorption, were assessed. Anthropometrics, duration of DM1, presence of complications, insulin dose, and degree of metabolic control were obtained from the patients' records. RESULTS: In children with DM1 and controls, the mean measurements of LS2-4 BMD were 0.698 +/- 0.178 g/cm2 and 0.669 +/- 0.192 g/cm2, respectively (p >0.05), and FN-BMD measurements were 0.743 +/- 0.147 g/cm2 and 0.744 +/- 0.170 g/cm2, respectively (p >0.05). Children with DM1 had lower serum levels of calcium, intact parathyroid hormone, osteocalcin and PINP, and higher serum levels of 25-hydroxyvitamin D and urinary Ca/Cr (p <0.05). BMD was not related to any of the markers of bone resorption or formation, duration of the disease, or degree of metabolic control. CONCLUSIONS: Although we did not establish decreased LS2-4 and FN-BMD measurements in patients with DM1, we found reduced bone formation and increased bone resorption markers in children with DM1. Measurements of serum osteocalcin, PINP, urinary Ntx and Ca/Cr might be useful for long-term follow-up in children and adolescents with DM1.

Prevalence and risk factors of obesity in school children in Antalya, Turkey.

OBJECTIVE: To determine the prevalence and risk factors of obesity and to obtain the age and gender-specific body mass index (BMI) percentiles in a cohort of children aged 6-17 years, living in the province of Antalya, Turkey. METHODS: The study included 15 schools throughout the city center of Antalya, Turkey during the period November 2002-March 2003. A total of 2465 school children (boys 1233, girls 1232) aged 6-17 years were chosen using a population based stratified cluster sampling method. We calculated the BMI (kg/m2) by measuring the weight and standing height. Overweight was defined as BMI between 85th and 95th percentile, and obesity as BMI above the 95th percentile. A questionnaire was distributed to the parents to determine obesity-related risk factors. RESULTS: The overall prevalence of obesity was 3.6% while overweight was 14.3%. According to gender, the prevalence of obesity in boys was 3.9% and overweight was 12.8%, while in girls, obesity was 3.2% and overweight was 15.8%. We found that obesity might be related with some factors such as number of regular meals, number of siblings, high birth weight, having computer at home, skipping breakfast and high socioeconomic status of parents. CONCLUSION: There is no difference in obesity prevalence among school children according to gender, but the mean BMI of girls is significantly higher than that of boys. Obesity prevalence among children in Antalya is very low compared to Europe and the United States.