Alterations in cortisol secretory dynamics in adolescent girls with anorexia nervosa and effects on bone metabolism.

Anorexia nervosa (AN) is associated with low bone density in adolescents and adults. Hypercortisolemia has been reported in adults with this disorder and has been hypothesized to be a factor in bone loss. However, the secretory dynamics of cortisol in adolescents with AN and the contribution of alterations in cortisol secretion to bone metabolism in AN have not been examined. We examined the dynamics of cortisol secretion by Cluster and deconvolutional analysis in 23 girls with AN and 21 healthy adolescents of comparable age and maturity. Cortisol sampling was performed every 30 min for 12 h overnight. Twenty-four-hour urinary free cortisol (UFC) and creatinine (cr) were obtained for all subjects. The surface area (SA) of the subjects was calculated. Markers of bone turnover (type 1 procollagen, osteocalcin, and N-telopeptide) were examined. Subjects with AN were prospectively followed over 1 yr, and those who recovered weight (defined as a 10% increase in body mass index) were again studied. On Cluster analysis, girls with AN had significantly higher mean cortisol (8.6 +/- 2.0 vs. 5.9 +/- 1.1 microg/dl; P < 0.0001), nadir cortisol (5.5 +/- 2.3 vs. 3.4 +/- 1.2 microg/dl; P = 0.0008), valley mean cortisol (7.0 +/- 2.7 vs. 4.7 +/- 1.5 microg/dl; P = 0.001), peak amplitude (12.6 +/- 4.4 vs. 7.8 +/- 3.0 microg/dl; P = 0.0004), peak area (652 +/- 501 vs. 340 +/- 238 microg/dl; P = 0.02), and total area under the curve (6112 +/- 1467 vs. 4117 +/- 802 microg/dl; P < 0.0001) than healthy adolescents. On deconvolutional analysis, the frequency of nocturnal secretory bursts (7.0 +/- 1.2 vs. 5.8 +/- 1.3 /12 h; P = 0.001), total nocturnal pulsatile cortisol secretion (69.3 +/- 14.7 vs. 53.9 +/- 11.1 microg/dl; P = 0.0003), and total cortisol secretion (89.6 +/- 18.8 vs. 71.2 +/- 17.6 microg/dl; P = 0.002) were significantly higher in girls with AN than in healthy controls. Cortisol half-life trended higher in girls with AN. However, basal cortisol secretion and approximate entropy did not differ between the groups. UFC/cr and UFC/cr.SA were significantly higher in girls with AN than in controls [0.050 +/- 0.028 vs. 0.036 +/- 0.017 (P = 0.04) and 0.035 +/- 0.020 vs. 0.023 +/- 0.012 (P = 0.03)]. Six of 23 girls with AN had UFC/cr.SA values that were more than 2 sd above those in healthy controls. An inverse correlation was noted between measures of cortisol concentration as well as pulsatile secretion and measures of nutritional status (body mass index, fat mass, leptin, insulin, and IGF-I). An oral glucose load suppressed cortisol levels in healthy adolescents, but not in AN patients. Weight recovery was associated with a significant decrease in the number of secretory bursts. In girls with AN, strong inverse correlations were noted between levels of cortisol (mean, nadir, and total area under the curve) and levels of markers of bone formation (C-terminal propeptide of type 1 procollagen and osteocalcin). Conversely, in healthy controls, cortisol values did not predict levels of markers of bone turnover. Adolescent girls with AN have significantly higher serum cortisol concentrations and UFC/cr.SA values than healthy adolescents. This increased cortisol concentration is a function of increased frequency of secretory bursts, resulting in increased pulsatile secretion. Hypercortisolemia appears to be a direct consequence of undernutrition and is associated with a decrease in markers of bone formation. Therefore, high cortisol values in AN may contribute to the low bone density observed in adolescents with this disorder by decreasing bone formation.

Hormonal and body composition predictors of soluble leptin receptor, leptin, and free leptin index in adolescent girls with anorexia nervosa and controls and relation to insulin sensitivity.

Anorexia nervosa (AN) is associated with very low levels of leptin, a cytokine secreted by adipose tissue and known to suppress appetite. Leptin may play a permissive role in onset of puberty and in resumption of gonadal function in conditions of undernutrition. The soluble leptin receptor (sOB-R) is the main leptin binding protein, and the ratio of serum leptin to sOB-R provides a measure of the free leptin index (FLI), which may be a more accurate determinant of leptin function. Determinants of sOB-R and FLI have not been examined in an adolescent population. We examined levels of sOB-R, leptin, and FLI, and body composition and hormonal determinants of these variables in 23 adolescent girls with AN and 21 healthy adolescent girls of comparable maturity prospectively over 1 yr. Measures of insulin resistance and adiponectin were also examined. We determined changes in levels of sOB-R, leptin, and FLI with weight recovery (defined as an increase in body mass index of >/=10%, n = 11), and with resumption of menstrual cycles (n = 13). Girls with AN had significantly higher levels of sOB-R (P = 0.0008) and significantly lower levels of leptin and FLI (P < 0.0001 for both) than healthy controls, and levels of FLI were reduced more than levels of leptin in girls with AN compared with controls. An inverse correlation was noted between levels of leptin and sOB-R for the group as a whole (r = -0.64, P < 0.0001) but not in girls with AN considered alone. The most important predictor of levels of sOB-R was cortisol in the group as a whole (r = 0.61, P < 0.0001) and in girls with AN considered alone (r = 0.66, P = 0.0008). Other independent predictors of sOB-R levels for the entire group were percent body fat (r = -0.44, P = 0.003) and levels of IGF-I (r = -0.37, P = 0.01). The most important predictors of leptin and FLI were body mass index and percent body fat. An inverse relationship was noted between measures of insulin resistance and sOB-R levels, whereas a positive association was noted between these measures and leptin and FLI. Adiponectin values did not differ in girls with AN compared with healthy controls and did not correlate with sOB-R, leptin, or FLI. Weight recovery resulted in significant decreases in levels of the sOB-R (24.7 +/- 1.7 to 17.6 +/- 1.2 U/ml, P = 0.004), and increases in levels of leptin (4.4 +/- 1.0 to 13.7 +/- 2.9 microg/liter, P = 0.02). Resumption of menstrual function, but not weight recovery alone, was associated with significant increases in FLI (0.19 +/- 0.04 to 0.50 +/- 0.09 microg/U x 10(-3), P = 0.02).We demonstrate an increase in levels of sOB-R and a decrease in the FLI in adolescent girls with AN, and also demonstrate that cortisol is the most important predictor of levels of sOB-R in this condition. Levels of leptin and FLI, conversely, are primarily predicted by body composition. Weight recovery is associated with a decrease in sOB-R and an increase in leptin. Resumption of menses is associated with significant increases in the FLI, suggesting that free leptin may be an important determinant of menstrual recovery.

Growth hormone and ghrelin responses to an oral glucose load in adolescent girls with anorexia nervosa and controls.

Anorexia nervosa (AN) is associated with high levels of GH and low levels of IGF-I suggestive of a nutritionally acquired lack of GH action or GH resistance. The suppression of GH levels after administration of inhibitors of GH secretion such as oral glucose is the definitive test to distinguish normal from pathological states of GH excess, such as acromegaly. However, suppression of GH by glucose has not been well characterized in states of adaptive GH excess, such as AN, especially in a younger adolescent population with relatively higher GH levels, compared with adults. In this study, we investigated GH suppression after a 100-g oral glucose load over a 1-h period in 19 adolescent girls with AN and 20 healthy controls of similar chronologic and bone age. We also compared nocturnal GH secretion characteristics by deconvolutional analysis in both groups to determine differences in secretory patterns between adolescents whose GH values suppressed vs. those whose values did not after oral glucose. Fasting levels of ghrelin, a GH secretagogue, and suppression of ghrelin with oral glucose were also determined to assess whether GH suppression or nonsuppression could be related to ghrelin values at respective time points. At 0 min (0') of the oral glucose tolerance test, girls with AN had significantly lower levels of glucose (P = 0.009) and higher levels of GH (P = 0.04) than controls. Nadir GH values were higher in AN than in controls (2.0 +/- 1.8 vs. 0.5 +/- 0.5 ng/ml, P = 0.001). Only 31.6% of girls with AN suppressed their GH values to 1 ng/ml or less vs. 85.0% of healthy adolescents (P = 0.0005). All healthy controls had nadir postglucose GH values of 2 ng/ml or less. Nadir GH concentrations during the oral glucose tolerance test correlated directly with all measures of GH secretion [basal (r = 0.37, P = 0.02), pulsatile (r = 0.56, P = 0.0002), and total (r = 0.57, P = 0.0002)]. Adolescent girls who did not suppress their GH values to 1 ng/ml or less had significantly higher levels of ghrelin at 0', 30', and 60' (P = 0.02, 0.004, and 0.008), significantly higher GH at 0' (P = 0.001), and higher nocturnal basal (P = 0.002), pulsatile (P = 0.05), and total GH secretion (P = 0.03) than those who did suppress below this level. Ghrelin values were higher in AN than in controls at each time point (P = 0.02, 0.0002, and 0.01 at 0', 30', and 60') but did not predict GH values at these time points. Adolescent girls with AN fail to adequately suppress their GH values after a 100-g oral glucose load. This lack of suppression may be related to the higher GH secretion seen in adolescents with this disorder. In contrast, all healthy adolescents suppress their GH values to 2 ng/ml or less but not 1 ng/ml or less after a glucose load. Although ghrelin values are higher in AN than in controls, we could not demonstrate a relationship between ghrelin and GH values. The inability of healthy girls to uniformly suppress GH levels to 1 ng/ml or less, a normal level defined for adults, may be related to higher GH secretion in the pubertal years, compared with adult life. Further studies are needed to define GH suppression in an adolescent population.

Measurement of free testosterone in normal women and women with androgen deficiency: comparison of methods.

Androgen deficiency in women is increasingly recognized as a new clinical syndrome and has raised our awareness of the importance of accurate and well-validated measurements of serum free testosterone (T) concentrations in women. Therefore, we compared serum free T levels measured by equilibrium dialysis to those measured by a direct RIA (analog method) and to those calculated from the law of mass action (requires the measurement of total T and SHBG). We also calculated the free androgen index, 100 x T/SHBG, as a simple index known to correlate with free T. Subjects were 147 women with variable androgen and estrogen statuses. All were studied three times in 1 month and included women 1) with regular menses (estrogen positive, T positive), 2) more than 50 yr old and not receiving estrogen (estrogen negative, T positive), 3) receiving estrogen (estrogen positive, T negative), and 4) with severe androgen deficiency secondary to hypopituitarism (estrogen negative, T negative). Calculated values for free T using the laws of mass action correlated well with those obtained from equilibrium dialysis (r = 0.99; P < 0.0001). However, the agreement depended strongly on the specific assays used for total T and SHBG. In contrast, the direct RIA method had unacceptably high systematic bias and random variability and did not correlate as well with equilibrium dialysis values (r = 0.81; P < 0.0001). In addition, the lower limit of detection was higher for the direct RIA than for equilibrium dialysis or calculated free T. Free androgen index correlates well with free T by equilibrium dialysis (r = 0.93; P < 0.0001), but is a unitless number without reference to the physical reality of free T. We conclude that the mass action equation and equilibrium dialysis are the preferred methods for use in diagnosing androgen deficiency in women.

Serum osteoprotegerin in adolescent girls with anorexia nervosa.

Low bone mineral density (BMD) in adolescents with anorexia nervosa (AN) is associated with a low bone turnover state. Osteoprotegerin (OPG), a cytokine that acts as a decoy receptor for receptor activator of nuclear factor-kappaB ligand, decreases bone resorption by inhibiting differentiation of osteoclast precursors and activation of mature osteoclasts, and by stimulating osteoclast apoptosis. We compared OPG levels in 43 adolescent girls with AN with 38 controls and examined bone density, bone turnover, and hormonal parameters. Girls with AN had lower fat mass, lean body mass, lumbar BMD z-scores, and lumbar bone mineral apparent density than controls. OPG levels were higher in girls with AN than in controls (44.5 +/- 22.5 pg/ml vs. 34.5 +/- 12.7 pg/ml, P = 0.02). Osteocalcin, deoxypyridinoline, estradiol, free testosterone, IGF-I, and leptin were lower in AN than in healthy adolescents. OPG values correlated negatively with body mass index (r = -0.27, P = 0.02), percent fat mass (r = -0.35, P = 0.0002), leptin (r = -0.28, P = 0.02), lumbar BMD z-scores (r = -0.25, P = 0.03), and lumbar bone mineral apparent density (r = -0.26, P = 0.03). In conclusion, adolescent girls with AN have higher serum OPG values than controls. OPG values correlate negatively with markers of nutritional status and lumbar bone density z-scores and may be a compensatory response to the bone loss seen in this population.