Beyond Body Mass Index - Body Composition Assessment by Bioimpedance in Routine Endocrine Practice.

OBJECTIVE: To explore the body composition of pediatric patients referred for endocrine evaluation. METHODS: This real-life observational study conducted between January 2018 and January 2020 included 10 001 clinic visits of 3500 children and adolescents; first visits of 5 to 18-year-old patients were included. Anthropometric data, blood pressure levels, pubertal status, and bioelectrical impedance analysis (BIA, Tanita MC-780 MA) were extracted from medical files. Excluded from the analysis were patients participating in other studies. RESULTS: A total of 1001 patients (48% boys, mean age 11.3 ± 3.4 years, 33.5% prepubertal) were included. Mean anthropometric z-scores were normal and similar for boys and girls. Sex differences in body composition were as follows: boys had lower fat percentage, lower truncal fat percentage, higher appendicular skeletal muscle mass, and a higher muscle-to-fat ratio (MFR) than girls (P < .001 for all). MFR correlated with body mass index-standard deviation scores (BMI-SDS) in overweight/obese patients (r = -0.558, P < .001), although not in underweight patients. Systolic blood pressure (SBP) correlated with BMI-SDS in overweight/obese patients (r = 0.262, P < .001), although not in underweight patients. Diastolic blood pressure (DBP) did not correlate with BMI-SDS in either group of extreme weight status. MFR correlated with SBP and DBP in overweight/obese patients (r = -0.230, P < .001 and r = -0.141, P = .018, respectively) as well as in underweight patients (r = 0.331, P < .001 and r = 0.264, P = .005, respectively). CONCLUSIONS: Our findings support BIA for a more refined characterization of patients referred for endocrine evaluation than BMI-SDS. MFR may be a better surrogate marker of blood pressure levels than BMI-SDS in both underweight and overweight/obese pediatric patients.

Cardiometabolic outcomes in children and adolescents with West syndrome.

BACKGROUND: West syndrome is a convulsive disorder of infancy with unique seizures and a characteristic background electroencephalograph pattern. Adrenocorticotropic hormone (ACTH) is effective in spasm cessation, yet metabolic consequences of this therapeutic agent in childhood have not been published. METHODS: In this observational study we explored the cardiometabolic outcomes of 117 children with West syndrome (78 ACTH-treated and 39 non-ACTH-treated) monitored at a single medical center from 1995 to 2019 (median follow-up 7.2 years). Outcomes included the prevalence of cardiometabolic derangements (obesity, hypertension, and dyslipidemia) during infancy (< 2 years), early childhood (2-6 years), and childhood/adolescence (6-18 years). RESULTS: The rates of metabolic derangements during infancy in the West syndrome cohort were high compared to childhood/adolescence (obesity 27.3 % vs. 3.3 %, [p = 0.010], diastolic hypertension 48.8 % vs. 5.1 % [p < 0.001], hypertriglyceridemia 71 % vs. 40 % [p = 0.008], low high-density lipoprotein cholesterol [HDL-c] 54.2 % vs. 12.9 % [p = 0.001], and elevated triglycerides/HDL-c ratios 62.5 % vs. 12.9 % [p < 0.001]). The proportion of systolic and/or diastolic blood pressure levels categorized as hypertensive was 58.5 % during infancy, 48.1 % during early childhood, and 26.3 % during childhood/adolescence. ACTH-treated patients had higher weight and weight-to-length z-scores and higher triglyceride levels during infancy compared to non-ACTH-treated patients (p = 0.008, p = 0.001, and p = 0.037, respectively), and higher triglyceride levels during early childhood (p = 0.050), with no significant group differences during childhood/adolescence. CONCLUSIONS: Children with West syndrome apparently have an increased prevalence of cardiometabolic derangements more pronounced in infants and in ACTH-treated patients. These findings highlight the need to monitor these children for cardiometabolic derangements, even though these cardiometabolic abnormalities are transitory and tend to decrease with time. The health implications of cardiometabolic derangements during critical windows of growth and development warrant further investigation.

WOMEN WITH NONCLASSIC CONGENITAL ADRENAL HYPERPLASIA HAVE GENDER, SEXUALITY, AND QUALITY-OF-LIFE FEATURES SIMILAR TO THOSE OF NONAFFECTED WOMEN.

Objective: Females with the severe classic forms of congenital adrenal hyperplasia reportedly have a higher frequency of atypical gender identity, nonheterosexual sexual relationships, and cross-gender role behavior. Comparable data and quality-of-life measures among those with the milder, more prevalent form, nonclassic congenital adrenal hyperplasia, are scarce. We aimed to assess health-related quality of life, gender identity, role, and sexual orientation in women with nonclassic congenital adrenal hyperplasia via a prospective, questionnaire-based, case-control study. Methods: Thirty-eight women with nonclassic congenital adrenal hyperplasia (median age 34 years; range, 18 to 44 years) and 62 age-matched female controls were recruited. Outcome measures included the Multi-Gender Identity, Sexuality, and World Health Organization (WHO) quality-of-life questionnaires. Results: Sociodemographic parameters (marital status, number of children, and educational level) were similar for both groups, as were most measures of the Multi-Gender Identity, Sexuality, and WHO quality-of-life questionnaires. However, "sometimes-feeling-as-a-man and sometimes-feeling-as-a-woman" were more frequently reported in the study group compared to the controls (7/38 [18.4%] vs. 3/62 [4.8%], respectively; P = .02). Furthermore, more nonclassic congenital adrenal hyperplasia women reported first falling in love with a woman (4/37 [10.8%] vs. 0/58 [0%]; P = .02). Conclusion: Our findings suggest possible subtle differences in gender identity and sexual orientation between adult nonclassic congenital adrenal hyperplasia females and controls. Quality of life was not impaired in individuals within the study group. The impact of exposure to mildly elevated androgen levels during childhood and adolescence on the female brain warrants more in-depth assessment in further studies. Abbreviations: CAH = congenital adrenal hyperplasia; Multi-GIQ = Multi-Gender Identity Questionnaire; NCCAH = nonclassic congenital adrenal hyperplasia; QoL = quality of life.

CHILDREN AND ADOLESCENTS WITH GENDER DYSPHORIA IN ISRAEL: INCREASING REFERRAL AND FERTILITY PRESERVATION RATES.

Objective: To describe patient characteristics at presentation, management, and fertility preservation rates among a cohort of Israeli children and adolescents with gender dysphoria (GD). Methods: We performed a retrospective chart review of 106 consecutive children and adolescents with GD (<18 years) referred to and followed at the multidisciplinary Israeli Pediatric Gender Dysphoria Clinic from March 2013 through December 2018. Results: Of the 106 patients, 10 were prepubertal (9 prepubertal transgender females), and 96 were pubertal (38 pubertal transgender females). The GD population increased 11-fold since the establishment of our clinic in 2013. The subject's median age at referral was 15.5 years (range, 4.6 to 18 years). At the time of referral, 91 (95%) of the pubertal group had completed sexual maturation in their assigned gender at birth. Thirteen (13.5%) patients had attempted suicide, and 11 (11.5%) reported having had suicidal thoughts. Fourteen (45%) pubertal transgender females and 3 (6.5%) pubertal transgender males completed fertility preservation. Gonadotropin-releasing hormone analog treatment was prescribed in 77 (80%) patients at a mean age of 15.9 ± 1.6 years. Gender-affirming hormones were prescribed in 61 (64%) patients at a mean age of 16.5 ± 1.3 years. No severe side effects were recorded. Two (2%) of the pubertal group expressed regret about medical treatment. Conclusion: Children and adolescents with GD are presenting for medical attention at increasing rates. Israeli adolescents with GD have high fertility preservation rates, perhaps attributable to cultural perspectives. Taking advantage of the option to preserve fertility can be achieved when proper counseling is both available and promoted by medical personnel. Abbreviations: GAH = gender-affirming hormone; GD = gender dysphoria; GnRHa = gonadotropin-releasing hormone analog; MHP = mental health professional.

HEALTH-RELATED QUALITY OF LIFE IN CHILDREN AND ADOLESCENTS WITH NONCLASSIC CONGENITAL ADRENAL HYPERPLASIA.

Objective: Nonclassic congenital adrenal hyperplasia (NCCAH) is a late-onset milder form of congenital adrenal hyperplasia that differs dramatically from the classic form. Health-related quality of life (HRQOL) in pediatric patients with the sole diagnosis of NCCAH has not been determined; therefore, in this study, we aimed to determine whether HRQOL is compromised in comparison to the general population. Methods: Single-center, cross-sectional, case-control study. Twenty-three hydrocortisone-treated children and adolescents (7 males) diagnosed with NCCAH by cosyntropin stimulation test and CYP21A2 gene mutation analysis were recruited to this study; 6 healthy siblings were also recruited. HRQOL was assessed by the child and parent-proxy PedsQL Inventory and compared between NCCAH subjects and healthy siblings. HRQOL scores of NCCAH subjects were compared with known standards from the U.S. and Israeli general healthy populations. Anthropometric measurements of children and parents were performed and compared between NCCAH subjects and healthy siblings. Pearson correlation coefficients were calculated. Results: HRQOL scores of the participants and parents did not differ between NCCAH subjects and healthy siblings. The HRQOL emotional domain scores of the NCCAH patients and parent were significantly lower than the healthy U.S. pediatric population (P = .046) but not different from established standards of the healthy Israeli population (P = .583). Anthropometric measurements were within the normal range and did not differ between NCCAH subjects and their siblings. Total, school functioning, and psychosocial HRQOL domain scores were positively correlated with body mass index-standard deviation score in NCCAH subjects. Conclusion: HRQOL was not adversely affected by NCCAH among adequately treated children and adolescents. Abbreviations: BMI = body mass index; CAH = congenital adrenal hyperplasia; HRQOL = health-related quality of life; NCCAH = nonclassic congenital adrenal hyperplasia; PedsQL = Pediatric Quality of Life Inventory; SDS = standard deviation score.

SERUM FREE CORTISOL DURING GLUCAGON STIMULATION TEST IN HEALTHY SHORT-STATURED CHILDREN AND ADOLESCENTS.

OBJECTIVE: The total cortisol (TC) response may be measured during the glucagon stimulation test (GST) for growth hormone (GH) reserve in order to assess the integrity of the hypothalamic-pituitary-adrenal (HPA) axis. Measurements of TC are unreliable in conditions of albumin and cortisol-binding globulin (CBG) alterations (e.g., hypoproteinemia or CBG deficiency). We aimed to measure the serum free cortisol (sFC) response to the GST in children and adolescents and determine whether it could predict the GH response to glucagon stimulation. METHODS: Infants and children with either short stature or growth attenuation who were referred for evaluation of GH reserve underwent the GST. RESULTS: The study population consisted of 103 subjects (62 females), median age 3.9 years (range, 0.5-14). The mean basal and peak TC levels were 13.3 ± 6.7 µg/dL and 29.6 ± 8.8 µg/dL, respectively. The mean basal and peak sFC levels were 0.7 ± 0.8 µg/dL and 1.7 ± 1.1 µg/dL, respectively. There was a negative correlation between peak TC and age ( r = -0.3, P = .007) but not between peak sFC and age ( r = -0.09, P = .36). Ninety-five percent of the patients had peak TC levels >15.8 µg/dL and peak sFC levels >0.6 µg/dL. CONCLUSION: Our results on a cohort of healthy short-statured children can serve as reference values for the sFC response during GST. Based on these results, we propose peak TC levels >15.8 µg/dL and peak sFC levels >0.6 µg/dL for defining normalcy of the HPA axis during the GST in children and adolescents. ABBREVIATIONS: ACTH = adrenocorticotrophic hormone BMI = body mass index CBG = cortisol-binding globulin GH = growth hormone GST = glucagon stimulation test HPA = hypothalamic-pituitary-adrenal SDS = standard deviation score sFC = serum free cortisol TC = total cortisol.

Probiotic supplementation in mothers of very low birth weight infants.

OBJECTIVE: Oral probiotic supplementation reduces the risk of necrotizing enterocolitis (NEC) in preterm infants. Concerns about safety and purity of probiotic preparations have limited their use in preterm infants. The authors administered probiotic bacteria to mothers of preterm infants, thereby avoiding the risks of direct exposure of infants to probiotic bacteria. DESIGN: This prospective, randomized, double blind, placebo-controlled trial at the Tel Aviv Medical Center (June 2007-November 2009) examined the effects of maternal oral probiotic supplementation on the incidence of NEC, death, and sepsis in very low birth weight (VLBW) infants fed with maternal breast milk. Mothers were assigned to supplementation with Lactobacillus acidophilus and Bifidobacteria lactis 2 × 10(E) [DOSAGE ERROR CORRECTED] CFU/d or to placebo starting from 1 to 3 days postpartum. The primary outcome measures were NEC, sepsis, and death. RESULTS: In total 49 mothers of 58 VLBW infants were recruited. A total of 25 infants were in the probiotic group and 33 in the placebo group. The overall incidence of Bell stage II to III NEC was 12%, with an incidence of 4% in the infants of the probiotic group and 18.2% in the placebo group (p = 0.12), respectively. Sepsis and mortality rates were similar. CONCLUSION: Postpartum maternal supplementation with probiotic bacteria may decrease the incidence of NEC in breastfed infants.

Mental health and timing of gender-related events among transgender and gender-diverse children and adolescents seeking gender-affirming consultation and care.

Transgender and gender-diverse (TGD) youth encounter unique challenges affecting their mental health, largely related to societal stigma and gender dysphoria. Limited research considers the specific needs of TGD youth. This study examined demographic and developmental factors, including the ages at which gender-related events occur, and their relationship to mental health among TGD youth seeking gender-affirming consultation and care (GACC). We examined the medical records of 674 TGD children and adolescents, comparing demographics, gender-related events, and mental health across gender groups. The total sample comprised 261 patients assigned male at birth, and 413 patients assigned female at birth. Non-binary individuals reported higher rates of psychopathology compared to binary transgender patients, with transgender boys exhibiting higher rates than transgender girls. Seeking GACC at a more advanced pubertal stage and older age was associated with an increased likelihood of psychopathology. Later recollection of first gender incongruence memory was correlated with higher rates of depression and anxiety. Finally, socioeconomic status was linked to GACC healthcare-seeking behaviors. These findings underscore the importance of recognizing the diverse experiences and needs of TGD youth seeking GACC services, highlighting that early identification and access to care may be crucial for improving mental health outcomes.

The role of physical examination in establishing the diagnosis of pneumonia.

BACKGROUND: Community-acquired pneumonia (CAP) is an important cause of acute respiratory disease in ambulatory care settings. The objective of this study was to assess the accuracy of medical history and physical examination in diagnosing CAP. METHODS: Pediatric residents prospectively completed a questionnaire documenting patients' medical history and physical examination whenever a chest radiograph was ordered on patients 1 month to 16 years of age. Chest radiographs were read by a pediatric radiologist. RESULTS: Of 525 children participating in the study, 181 (34%) demonstrated findings of pneumonia. Thirty-four (19%) had no symptoms other than fever, and 51 (28%) had normal lung auscultation. Pediatric residents had the same interpretation in 85% of cases in which radiographic CAP was diagnosed by the radiologist, and in 76% of cases in which radiographic pneumonia was excluded by the radiologist. CONCLUSIONS: Results demonstrate the significant added value of chest radiography as an ancillary test for diagnosis of pneumonia in the emergency department setting.

Human milk fatty acids profile changes during prolonged lactation: a cross-sectional study.

BACKGROUND: Human milk produced during prolonged lactation (> 1 year) is extraordinarily rich in fat and has a higher energy content than human milk produced during short lactation. OBJECTIVES: To estimate the fatty acid (FA) profile of human milk and to test the hypothesis that the proportion of C12 and C14 (two dietary saturated FA known to most promote hypercholesterolemia) in human milk during prolonged lactation is similar to that in short lactation. METHODS: We conducted a cross-sectional study of 30 mothers of term infants lactating for more than 1 year as compared with 25 mothers of full-term infants who lactated for 2-6 months. Milk was collected by manual expression in mid-breastfeeding. RESULTS: The two groups did not differ in maternal height, weight, body mass index, diet, infant birth weight and gestational age, but mothers in the prolonged lactation group were significantly older. There was a significant correlation between lactation duration and C12 or C14. The percentage of all FA combined (except for C12 and C14) decreased significantly overtime. In contrast, C12:0 and C14:0 combined increased significantly during lactation (R2 = 10.0%, P < 0.03). CONCLUSIONS: Women who lactated for more than 1 year had higher C12 and C14 FA percentages in their milk than women who lactated for 2-6 months.

Adolescent Transgender Females Present Impaired Semen Quality That Is Suitable for Intracytoplasmic Sperm Injection Even Before Initiating Gender-Affirming Hormone Treatment.

The present study aimed to determine the semen quality and cryopreservation outcomes among adolescent transgender females at the time of fertility preservation (FP) before initiating gender-affirming hormone (GAH) treatment. This retrospective cohort study included 26 adolescent transgender females who underwent FP in our Fertility Institute between 06/2013 and 10/2020. Pre-freezing semen parameters were compared to WHO 2010 reference values. Post-thaw semen parameters were used to determine the adequate assisted reproductive technology (ART). A multivariate linear regression analysis was performed to assess the impact of medical and lifestyle factors on semen quality. The mean age at which adolescent transgender females underwent FP was 16.2 ± 1.38 years. The median values of all semen parameters in our study group were significantly lower compared to the WHO data, including volume (1.46 mL vs 3.2 mL, respectively, P = 0.001 ), sperm concentration (28 × 106/mL vs 64 × 106/mL, P < 0.001), total sperm number (28.2 × 106 vs 196 × 106, P < 0.001), total motility (51.6% vs 62%, P < 0.001), and normal morphology (2% vs 14%, P < 0.001). The frequency of semen abnormalities was teratozoospermia 72%, hypospermia 52%, oligozoospermia 28%, and azoospermia 4%. The median post-thaw total motile count was 0.17 × 106/vial, and the quality was adequate only for ICSI in 87.7% of the thawed semen samples. No correlation was found between selected medical and lifestyle factors and poor semen parameters. Semen quality is strongly reduced among adolescent transgender females before hormone therapy and their stored sperm samples are suitable for intracytoplasmic sperm injection (ICSI) rather than conventional IVF/intrauterine insemination (IUI).

Blood pressure dynamics after pubertal suppression with gonadotropin-releasing hormone analogs followed by estradiol treatment in transgender female adolescents: a pilot study.

OBJECTIVES: The benefits of gonadotropin-releasing hormone analogues (GnRHa) in the treatment of central precocious puberty are well established, and their use is regarded as both safe and effective. Possible adverse effects on blood pressure (BP) and cardiac outcomes, body composition, bone health and brain development, however, continue to be of some concern. The aim of this study was to analyze BP changes in transgender female adolescents before and after receiving GnRHa and after adding estrogen treatment. METHODS: This was a retrospective pilot study. We analyzed systolic BP (SBP) and diastolic BP (DBP) before and after GnRHa initiation and after adding estrogen. RESULTS: Nineteen transgender female adolescents received GnRHa and 15 continued to estrogen treatment. Their baseline SBP and DBP percentiles did not change significantly after either GnRHa or the addition of estrogen treatment. CONCLUSIONS: Blood pressure is apparently not affected by GnRHa or GnRHa + estrogen treatment in transgender female adolescents. Further larger studies are indicated to confirm these findings.

Type 1 diabetes outcomes of children born in Israel of Eritrean asylum seekers.

AIMS: Disparities in health outcomes in pediatric type 1 diabetes (T1D) based on race/ethnicity and socioeconomic position (SEP) have been reported. We compared T1D characteristics between Eritrean status-less children living in Israel and native-born Israeli children. METHODS: This observational study compared 7 Eritrean and 28 Israeli children (< 8 years old at T1D diagnosis) who were diagnosed in a single diabetes center during 2015-2019. Sociodemographic and diabetes-related data from diagnosis until the last clinic visit were retrieved from their medical files. RESULTS: At diagnosis, the mean age was 4.8 ± 2.2 years, 17 (48.6%) had diabetic ketoacidosis with a mean HbA1c level of 10.5 ± 2.1% (91.3 mmol/mol) and 29 (82.9%) had ≥ 2 pancreatic autoantibodies. The mean T1D duration of follow-up was 2.7 ± 1.4 years. Overall glycemic control during follow-up (> 6 months from diagnosis, mean number of samples 10.6 ± 5.2) was good, with mean, best, and peak HbA1c levels of 7.4 ± 0.8% (57.4 mmol/mol), 6.7 ± 0.7% (49.7 mmol/mol), and 8.1 ± 1.1% (65 mmol/mol), respectively. Thirty-two children (91.4%) used continuous glucose monitoring devices (CGMs), and the mean time from diagnosis to CGM initiation was 10.8 ± 14.1 months. CGM metrics: time CGM active: 95.4 ± 3.8%, mean glucose level: 170.0 ± 27.0 mg/dl (9.4 mmol/L), time-in-range: 56.4 ± 14.7%, time-below-range: 5.5 ± 5.7%, and time-above-range: 38.6 ± 16.1%. Diabetes-related parameters at diagnosis and during follow-up were similar between groups. Eritrean children had significantly lower SEPs (P < 0.001) and parental education levels (P < 0.001). Correlations between SEP and diabetes parameters and SEP and growth parameters were not significant. CONCLUSIONS: Eritrean status-less children in Israel achieved glycemic targets similar to those of Israeli children, perhaps reflecting uniformity in the standard of care and CGM usage.

Blood Pressure Dynamics After Pubertal Suppression with Gonadotropin-Releasing Hormone Analogs Followed by Testosterone Treatment in Transgender Male Adolescents: A Pilot Study.

Purpose: We analyzed blood pressure (BP) changes in transgender male adolescents treated with gonadotropin-releasing hormone analogs (GnRHa) and after adding testosterone treatment. Methods: This was a retrospective pilot study. Outcome measures included systolic BP (SBP) and diastolic BP (DBP) before and after GnRHa initiation and after adding testosterone. Results: Fifteen transgender male adolescents received GnRHa. DBP percentiles increased significantly after GnRHa treatment (from 55.9% ± 26.4 to 73.6% ± 9.4, p = 0.019). BP levels did not meet criteria for hypertension. DBP percentiles were restored after adding testosterone. Conclusion: GnRHa may increase DBP in transgender male adolescents, and testosterone treatment may restore it. Further larger studies are indicated.

The effect of CAG repeats length on differences in hirsutism among healthy Israeli women of different ethnicities.

PURPOSE: Variations in the degree of hirsutism among women of different ethnic backgrounds may stem from multiple etiologies. Shorter length of the polymorphic CAG repeats of the androgen receptor (AR) gene may be associated with increased activity of the receptor leading to hirsutism. We hypothesized that there are ethnic differences in the degree of hirsutism that is unrelated to androgen levels among Israeli women, and that the CAG repeats length may contribute to these differences. Anti-androgenic therapies, such as spironolactone, could be suggested if a shorter CAG repeats length is found to affect the difference in the degree of hirsutism between the ethnic groups. METHODS: Healthy Israeli Jewish women aged 18-45 years of Ashkenazi and non-Ashkenazi origin were invited to participate. Hirsutism was assessed using the simplified Ferriman-Gallwey (sFG) score, and serum total testosterone levels were measured as well. The CAG repeats length was determined by PCR. Methylation-sensitive methods were used to detect the fractional activity of each allele, and the weighted mean was calculated for the CAG repeats length. RESULTS: One-hundred and eight women were recruited (49 Ashkenazi and 59 non-Ashkenazi). The Ashkenazi women had a significantly lower degree of hirsutism (P<0.01), lower mean BMI (P = 0.003), total testosterone levels (P = 0.017), and longer weighted bi-allelic CAG repeats mean (P = 0.015) compared to non-Ashkenazi women. For the group as a whole, there was a significant negative correlation between the number of CAG repeats in the AR gene and the sFG score, while the number of repeats was not related to testosterone levels. Stepwise logistic regression revealed that ethnic origin and the CAG repeats length were the strongest factors affecting hirsutism (P<0.001, P = 0.03, respectively). CONCLUSIONS: There is a significant difference in the degree of hirsutism between Ashkenazi and non-Ashkenazi women in Israel that is partially explained by CAG repeats length.

Correction: The effect of CAG repeats length on differences in hirsutism among healthy Israeli women of different ethnicities.

[This corrects the article DOI: 10.1371/journal.pone.0195046.].

Combining mouse mammary gland gene expression and comparative mapping for the identification of candidate genes for QTL of milk production traits in cattle.

BACKGROUND: Many studies have found segregating quantitative trait loci (QTL) for milk production traits in different dairy cattle populations. However, even for relatively large effects with a saturated marker map the confidence interval for QTL location by linkage analysis spans tens of map units, or hundreds of genes. Combining mapping and arraying has been suggested as an approach to identify candidate genes. Thus, gene expression analysis in the mammary gland of genes positioned in the confidence interval of the QTL can bridge the gap between fine mapping and quantitative trait nucleotide (QTN) determination. RESULTS: We hybridized Affymetrix microarray (MG-U74v2), containing 12,488 murine probes, with RNA derived from mammary gland of virgin, pregnant, lactating and involuting C57BL/6J mice in a total of nine biological replicates. We combined microarray data from two additional studies that used the same design in mice with a total of 75 biological replicates. The same filtering and normalization was applied to each microarray data using GeneSpring software. Analysis of variance identified 249 differentially expressed probe sets common to the three experiments along the four developmental stages of puberty, pregnancy, lactation and involution. 212 genes were assigned to their bovine map positions through comparative mapping, and thus form a list of candidate genes for previously identified QTLs for milk production traits. A total of 82 of the genes showed mammary gland-specific expression with at least 3-fold expression over the median representing all tissues tested in GeneAtlas. CONCLUSION: This work presents a web tool for candidate genes for QTL (cgQTL) that allows navigation between the map of bovine milk production QTL, potential candidate genes and their level of expression in mammary gland arrays and in GeneAtlas. Three out of four confirmed genes that affect QTL in livestock (ABCG2, DGAT1, GDF8, IGF2) were over expressed in the target organ. Thus, cgQTL can be used to determine priority of candidate genes for QTN analysis based on differential expression in the target organ.