Sex hormone binding globulin levels in adolescent subjects with diabetes mellitus

Adiposity, chronic inflammation, and the prepubertal decline of sex hormone binding globulin in children: evidence for associations with the timing of puberty (Earlybird 58)

BACKGROUND

The regulation and role of SHBG in children are poorly defined. Here we investigated whether adiposity-related mechanisms regulate SHBG and whether SHBG levels are associated with the age of puberty.

METHODS

Longitudinal modelling of annual physiological and endocrine measurements from age 5 to 15 years in a cohort of 347 Plymouth schoolchildren.

RESULTS

SHBG levels were highest at age 5 years and then declined. Mean (SE) SHBG levels were higher in boys than girls at age 5 years [mean (SE) difference 7.68 (3.80) nmol/L; P = .045] but lower in boys by age 15 years [difference 12.19 (3.4) nmol/L; P < .001]. SHBG correlated inversely with adiposity [body mass index SD score (BMI SDS)], insulin, IGF-I, C-reactive protein (CRP), and leptin and positively with adiponectin but not with dehydroepiandrosterone sulphate, androstenedione, or T. In linear mixed models, five adiposity-related covariates (insulin, leptin, adiponectin, IGF-I, and CRP) all exerted significant main effects on SHBG (boys P = .04 to < .001; girls P = .007 to < .001). However, the further addition of BMI SDS rendered the effects of leptin, insulin, and adiponectin nonsignificant, whereas CRP and IGF-I remained significant. In separate models, the individual effects on SHBG of insulin, leptin, IGF-I, and adiponectin, but not CRP, were displaced by BMI SDS. Finally, in linear regression, BMI SDS little affected R(2) resulting from the five adiposity-related signals. Girls with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, tended to have earlier LH secretion, and earlier age at peak height velocity and menarche. In contrast, boys with lower SHBG levels at age 5 years reached Tanner stage 2 earlier, but there were no relationships between SHBG and earlier onset of LH secretion or age at peak height velocity.

CONCLUSIONS

Adiposity-related endocrine mechanisms and chronic inflammation were associated with the prepubertal decline of SHBG, and lower SHBG levels anticipated earlier puberty. These findings may be relevant to the occurrence of earlier puberty in recent decades.

Heart rate variability in pubertal girls with type 1 diabetes: its relationship with glycaemic control, insulin resistance and hyperandrogenism

OBJECTIVE

To examine the association between glycaemic control, insulin resistance and hyperandrogenism on cardiac autonomic function in peripubertal girls with type 1 diabetes.

DESIGN

Prospective, clinic-based study of 125 girls with diabetes and 46 age-matched nondiabetic girls.

MEASUREMENTS

Heart rate variability (HRV) parameters derived from a 10-min ECG recording using LabChart Pro were as follows: standard deviation of mean NN intervals (SDNN), where NN = adjacent QRS complexes; root mean squared difference of successive NN intervals (RMSSD) - estimates of overall HRV; and low-/high-frequency (LF:HF) ratio - an estimate of the sympathovagal balance. Androgens and sex hormone binding globulin (SHBG) were measured in girls with diabetes, and free androgen index (FAI) calculated. HRV and anthropometry were measured in nondiabetic controls.

RESULTS

Adolescents with diabetes (median age 15·1 years [13·3-16·0], diabetes duration 7·0 years [4·6-10·0] and median HbA1c 8·4% [7·5-9·3]) had higher HR and lower HRV compared with controls. Using multivariate models in the diabetes group, higher HR was associated with higher HbA1c, total daily dose insulin/kg body weight and systolic BP standard deviation scores (SDS), whilst reduced HRV was associated with higher HbA1c (SDNN, RMSSD and LF:HF ratio), lower SHBG (SDNN and RMSSD) and higher weight SDS (LF:HF ratio). Higher FAI was associated with higher HR and reduced HRV measures in the univariate analyses only.

CONCLUSIONS

In adolescent girls with diabetes, reduced HRV parameters are associated with worse glycaemic control, lower SHBG and higher weight SDS. SHBG should be considered in the cardiac risk models for this population.

Puberty as an accelerator for diabetes complications

Much is written about how difficult it is to deal with diabetes during adolescence, and rightly so. Less is understood as to how puberty may be an accelerator of vascular complications. With the increase in childhood diabetes, complication risks need to be revisited in relation to puberty and the secular increase in adiposity. Recent data suggest greater risk for severe vascular complications in those with diabetes during puberty, compared with young people who develop diabetes after puberty. It is also widely recognized that higher hemoglobin A1c (HbA1c) results are often seen during the pubertal period. This article will review complication outcomes in relation to puberty and examine mechanisms by which puberty may modify risk above glycemic exposure, and possible gender disparities in the risk of complications in the adolescent period.

Genetic and Molecular Basis of QTL of Diabetes in Mouse: Genes and Polymorphisms

A systematic study has been conducted of all available reports in PubMed and OMIM (Online Mendelian Inheritance in Man) to examine the genetic and molecular basis of quantitative genetic loci (QTL) of diabetes with the main focus on genes and polymorphisms. The major question is, What can the QTL tell us? Specifically, we want to know whether those genome regions differ from other regions in terms of genes relevant to diabetes. Which genes are within those QTL regions, and, among them, which genes have already been linked to diabetes? whether more polymorphisms have been associated with diabetes in the QTL regions than in the non-QTL regions.

Our search revealed a total of 9038 genes from 26 type 1 diabetes QTL, which cover 667,096,006 bp of the mouse genomic sequence. On one hand, a large number of candidate genes are in each of these QTL; on the other hand, we found that some obvious candidate genes of QTL have not yet been investigated. Thus, the comprehensive search of candidate genes for known QTL may provide unexpected benefit for identifying QTL genes for diabetes.

Sex hormone-binding globulin and testosterone in individuals with childhood diabetes

OBJECTIVE

Insulin downregulates hepatic production of sex hormone-binding globulin (SHBG), which in turn influences sex hormone bioavailability. The effects of childhood-onset diabetes and insulin resistance in nondiabetic individuals on SHBG and testosterone in children and young adults are poorly understood.

RESEARCH DESIGN AND METHODS

Individuals with diabetes diagnosed at <18 years of age (n = 48) and their siblings without diabetes (n = 47) were recruited for the Chicago Childhood Diabetes Registry Family Study. SHBG and total and free testosterone were measured. Participants ranged in age from 10 to 32 years; 39% were non-Hispanic white. The majority of individuals with diabetes had the classic type 1 phenotype (75%), while the remainder exhibited features of type 2 or mixed diabetes; 96% were treated with insulin.

RESULTS

SHBG and total testosterone were higher in male subjects with diabetes compared with those in male siblings. Elevated SHBG was associated with the absence of endogenous insulin independent of sex; elevated total testosterone was similarly associated with the absence of C-peptide for male subjects only. Diabetes type and treatment were unrelated. In those without diabetes, greater insulin resistance had a small, nonsignificant association with lower SHBG and higher free testosterone.

CONCLUSIONS

SHBG and total testosterone appear to be higher in male children and young adults with diabetes compared with nondiabetic male siblings, which is apparently related to the absence of endogenous insulin. This may have implications for sex hormone-dependent processes across the lifespan in male individuals diagnosed with diabetes as children.

Steroids in adult men with type 1 diabetes: a tendency to hypogonadism

OBJECTIVE

To compare steroids and their associations in men with type 1 diabetes and healthy control subjects.

RESEARCH DESIGN AND METHODS

We studied 52 adult men with type 1 diabetes without microvascular complications, compared with 53 control subjects matched for age and BMI. Steroids and their binding globulins were assessed in a single venous blood sample and a 24-h urine sample.

RESULTS

In adult men with type 1 diabetes, total testosterone did not differ from healthy control subjects, but sex hormone-binding globulin (SHBG) (42 [14-83] vs. 26 [9-117] nmol/l, P < 0.001), cortisol-binding globulin (CBG; 0.87 +/- 0.17 vs. 0.73 +/- 0.10 nmol/l, P < 0.001), and cortisol levels (0.46 +/- 0.16 vs. 0.39 +/- 0.14 nmol/l, P < 0.01) were higher. The free testosterone index was lower (60 [17-139] vs. 82 [24-200], P < 0.001), and the calculated free testosterone was slightly lower (497 [115] vs. 542 [130], P < 0.064), but the pituitary-gonadal axis was not obviously affected in type 1 diabetes. The calculated free serum cortisol was not different, and 24-h urinary free cortisol excretion was lower in type 1 diabetes (121 [42-365] vs. 161 [55-284] nmol/24 h, P < 0.009). Testosterone was mainly associated with SHBG. Estimated portal insulin was a contributor to SHBG in control subjects but not in type 1 diabetes. Cortisol was associated with CBG. HbA(1c) contributed to CBG in men with diabetes but not in control subjects, whereas estimated portal insulin did not contribute.

CONCLUSIONS

Adult men with fairly controlled type 1 diabetes without complications who are treated with subcutaneous insulin have a tendency to hypogonadism, as reflected by lower free testosterone levels in the presence of similar total testosterone levels and higher SHBG levels.

Serum androgen levels in adolescents with type 1 diabetes: relationship to pubertal stage and metabolic control

Delayed sexual maturation is still frequently seen in adolescents with type 1 diabetes. A close relationship between insulin and androgen metabolism has been found in a number of studies. Our study was designed to investigate whether or not abnormalities in androgen secretion could play a role in the onset of sexual maturation in adolescents with type 1 diabetes. We have asked whether or not there was a correlation between daily insulin dosage, duration of diabetes, metabolic control, age, pubertal stage, and body mass index (BMI) versus serum androgen concentrations. Basal total and free testosterone, dehydroepiandrosterone-sulfate (DHEA-S), dihydrotestosterone (DHT), sex hormone binding globulin (SHBG) and 3alpha-androstanediol glucuronide (3alpha diol-G) plasma concentrations were measured in 36 pubertal boys and 31 pubertal girls with type 1 diabetes and in 59 sex- and pubertal stage-matched control subjects without diabetes. Significantly higher serum total testosterone (p<0.01) and free testosterone (p<0.05) levels were found in females and males with type 1 diabetes than in controls at pubertal stage 5. DHEA-S, SHBG, DHT and 3alpha diol G concentrations in patients with diabetes were not significantly different from those in controls. There was no correlation between daily insulin requirements and serum androgen levels. These data suggest that adolescents with diabetes have similar serum levels of DHEA-S, SHBG, DHT and 3alpha diol G as healthy subjects at all stages of puberty. However, there are significant differences in serum testosterone and free testosterone levels in adolescents with diabetes when compared to healthy, sex- and pubertal stage-matched controls in late puberty. We hypothesize that the increased testosterone levels in patients with diabetes could relate to reduced fertility in females, disorders of sexual maturation and an increased risk for cardiovascular complications later in life.

Sex hormone-binding globulin and insulin resistance in African-American women

Sex hormone-binding globulin (SHBG) binds testosterone, determining the level of free, biologically active hormone, and is a sensitive indicator of androgen status in women. SHBG is strongly correlated with high-density lipoprotein (HDL), central obesity, and insulin sensitivity in Caucasian and Mexican-American women, thereby acting as a biologic marker for cardiovascular disease risk. The purpose of this study was to determine if SHBG was a significant correlate of metabolic cardiovascular risk factors in African-American women. Eighty-one nondiabetic, normotensive African-American women were enrolled (mean age, 30 years). After excluding women on oral contraceptives (n = 19), 62 women were examined during the follicular phase of the menstrual cycle. All subjects underwent an oral glucose tolerance test (OGTT) and a euglycemic-hyperinsulinemic insulin clamp, and the lipid and sex hormone levels were measured. Correlation analyses showed a significant correlation between SHBG and the following variables in women: central obesity, body mass index (BMI), HDL cholesterol, apolipoprotein B (apoB), insulin sensitivity adjusted for lean mass (M'), and the sum of insulin during the OGTT. The strongest correlates of SHBG in women were measures of insulin resistance (r = .421, P < .001). SHBG appears to be a biologic marker for insulin resistance, which is linked to cardiovascular risk, in African-American women.

Weight loss and wrestling training: effects on growth-related hormones

Adolescent wrestlers (n = 9, 15.4 yr) and recreationally active control males (n = 7, 15.7 yr) were measured before, at the end of, and 3.5-4 mo after a competitive wrestling season to assess the influence of dietary restriction on growth-related hormones. Wrestlers had significant elevations preseason to late season for morning serum concentrations (mean of 8 serial samples) of growth hormone (GH; 2.9 +/- 0.7 vs. 6.5 +/- 1.4 ng/ml) and sex hormone-binding globulin (SHBG; 16.1 +/- 2.3 vs. 27.9 +/- 6.9 nmol/l) and significant reductions in GH-binding protein (GHBP; 178 +/- 19 vs. 109 +/- 17 pmol/l), insulin-like growth factor I (IGF-I; 332 +/- 30 vs. 267 +/- 34 ng/ml), testosterone (T; 4.9 +/- 0.4 vs. 3.6 +/- 0.4 ng/ml), and free testosterone (Free-T; 22.4 +/- 3.6 vs. 15.7 +/- 2.8 pg/ml). Wrestlers had significant postseason reductions in GH (3.44 +/- 1.30 ng/ml) and SHBG (10.43 +/- 4.13 nmol/l) but elevations in GHBP (66.7 +/- 23.8 pmol/l), IGF-I (72.9 +/- 25.1 ng/ml), T (2.10 +/- 0.46 ng/ml), and Free-T (9.76 +/- 3.01 pg/ml). Concentrations of luteinizing hormone (LH), estradiol, prolactin, cortisol, insulin, and thyroid hormones did not differ because of exercise-dietary practices of wrestlers. In-season elevations in GH, with concomitant reductions in GHBP and IGF-I, that were reversed during the postseason suggest a reduction in GH receptor number and partial GH resistance during the season. Nonelevated LH with reduced T levels suggests a central hypothalamic-pituitary-gonadal (H-P-G) axis impairment. In conclusion, undernutrition may lead to altered H-P-G and GH-IGF-I axes function in adolescent wrestlers. However, only the wrestlers' late-season Free-T concentrations were outside the normal range, and the hormone axis impairments were quickly reversed. The present data do not address hormonal axis responses to several years of wrestling and weight loss.

Indications of low sex hormone binding globulin (SHBG) in young females with type 1 diabetes, and an independent association to microalbuminuria

Sex hormone binding globulin (SHBG) is normally decreased during puberty and inversely related to insulin resistance. Microalbuminuria is rare before puberty in Type 1 diabetes implicating that sex hormones may contribute to its development. We investigated SHBG levels in young females with > 5 years of Type 1 diabetes, and the association to microalbuminuria. Ten diabetic females with, and 15 without microalbuminuria, and 17 healthy controls in pubertal stage 4-5 were compared regarding anthropometric data, fasting serum levels of SHBG, testosterone, insulin, insulin-like growth factor-1 (IGF-1), lipids and lipoproteins. Multiple regression analyses were performed to study variables with independent influences on SHBG and albumin excretion rate (AER), respectively, in Type 1 diabetes. SHBG was lower and testosterone/SHBG ratio higher in normoalbuminuric females with diabetes than in controls. This was further emphasized in diabetic patients with microalbuminuria. IGF-1 was lower in Type 1 diabetes than in controls, and significantly decreased in microalbuminuric as compared to normoalbuminuric diabetic patients. IGF-1 was only correlated to SHBG in healthy controls. In Type 1 diabetes, applying stepwise multiple regression analysis, insulin dose, BMI, and HbA1c had a significant and independent inverse influence on SHBG (r2 = 0.77, p < 0.001). With log AER as the dependent variable, low SHBG, low IGF-1, HbA1c, and age added to the regression (r2 = 0.65, p = 0.004), whereas BMI, insulin dose and blood pressure did not. In conclusion, SHBG is decreased in young females with Type 1 diabetes, influenced by increased insulin requirements, BMI and HbA1c. In turn, low SHBG seems to be independently associated to elevated AER in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Menstrual irregularities are more common in adolescents with type 1 diabetes: association with poor glycaemic control and weight gain

Ovarian function in post-menarchal girls with Type 1 diabetes was evaluated. Menstrual histories from 24 adolescents with Type 1 diabetes were compared with those from 24 age and sex matched controls. A fasting blood sample was obtained from subjects with Type 1 diabetes for the measurement of ovarian and adrenal sex hormones, LH and FSH, glucose and insulin, insulin-like growth factor-I (IGF-I), and insulin-like growth factor binding protein-1 (IGFBP-1); and an ovarian ultrasound scan was performed. Menstrual irregularity was more prevalent in patients with Type 1 diabetes than controls (54% vs 21%, p < 0.01) and their mean body mass index (BMI) was greater (22.3 +/- 0.5 (+/- SEM) vs 20.7 +/- 0.6 kg m-2, p < 0.05). Subjects with Type 1 diabetes with irregular menses (when compared with diabetic subjects with a regular cycle) had a significantly higher HbA1 (12.8 +/- 0.4 vs 10.5 +/- 0.5%, p < 0.01) and BMI (23.2 +/- 0.6 vs 21.4 +/- 0.6 kg m-2, p < 0.05) associated with a lower sex hormone binding globulin (SHBG) (37.2 +/- 4.0 vs 52.6 +/- 4.0 nmol l-1, p < 0.025) and IGF-I (1.4 +/- 0.2 vs 2.2 +/- 0.2 mUI-1, p < 0.025) and a higher LH:FSH ratio (2.6 +/- 0.5 vs 1.4 +/- 0.2, p < 0.05). Polycystic ovarian changes were identified in 10/13 (77%) of these patients with an irregular cycle. Menstrual irregularity is common in post-menarchal girls with Type 1 diabetes and is associated with poor glycaemic control and weight gain. The apparent high incidence of polycystic ovarian change requires further investigation.

Growth during childhood and final height in type 1 diabetes

The growth of 184 children with Type 1 diabetes was analysed using data collected prospectively in the Oxford district between 1969 and 1992. The overall mean height standard deviation score (Ht SDS +/- SD) at diagnosis was 0.35 +/- 1.05 which was significantly greater than the national standard of Tanner (1966). However, there is evidence of a secular trend in the heights of Oxford children over the last 20 years when compared with Tanner. When data from children with diabetes were compared with local controls, it was only the children aged 5-10 years at diagnosis who were taller (Ht SDS +/- SD, 0.58 +/- 1.14, versus 0.31 +/- 0.90, n = 73, p < 0.05). Those diagnosed under the age of 5 years (n = 37) were shorter (Ht SDS 0.12 +/- 0.93) and those diagnosed aged more than 10 years (n = 74) were similar in size (Ht SDS 0.22 +/- 0.98) to controls. These differences could not be explained by social class. Loss of height occurred between diagnosis and puberty, particularly in those diagnosed between the ages of 5 and 10 years. The pubertal growth spurt was blunted in all groups but this abnormality was more profound in the girls (mean peak height velocity SDS -1.09 +/- 1.02, p < 0.0005) than in the boys (mean peak height volocity SDS -0.5 +/- 1.14, p < 0.025). The mean final height SDS was -0.74 +/- 0.96 in those diagnosed < 5 years, 0.00 +/- 1.26 in those diagnosed between the ages of 5 and 10 years and 0.09 +/- 1.10 in those aged more than 10 years at diagnosis.(ABSTRACT TRUNCATED AT 250 WORDS)