Vertebral morphology in aromatase inhibitor-treated males with idiopathic short stature or constitutional delay of puberty

Aromatase inhibitors (AIs), blockers of estrogen biosynthesis, delay bone maturation and therefore are used increasingly to promote growth in children and adolescents with growth disorders. The effects of treatment on skeletal health are largely unknown. Since estrogen deficiency is associated with various detrimental skeletal effects, we evaluated in this cross-sectional posttreatment study vertebral body morphology, dimensions and endplates, and intervertebral disks by the use of magnetic resonance imaging (MRI) in two cohorts of males previously treated with the AI letrozole or placebo. Males with idiopathic short stature received treatment with letrozole or placebo for 2 years during prepuberty or early puberty; males with constitutional delay of puberty received letrozole or placebo in combination with low-dose testosterone for 1 year during early or midpuberty. In males with idiopathic short stature, mild vertebral body deformities were found in 5 of 11 (45%) letrozole-treated subjects, whereas in the placebo group no deformities were detected (p = .01). In the cohort of males with constitutional delay of puberty, a high prevalence of endplate and intervertebral disk abnormalities was observed in both the letrozole- and the placebo-treated groups. We conclude that AI therapy during prepuberty or early puberty may predispose to vertebral deformities, which probably reflect impaired vertebral body growth rather than impaired bone quality and compression fractures. If AIs are used in growth indications, follow-up of vertebral morphology is indicated.

A novel low molecular weight inhibitor of focal adhesion kinase and insulin-like growth factor-1 receptor, TAE226, inhibits glioma growth

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Background: Glioblastomas are highly lethal cancers that resist current therapies. Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase overexpressed in glioblastoma patient specimens that may promote glioma growth and invasion by increasing cellular adhesion, migration, invasion, proliferation. TAE226 is a novel low molecular weight inhibitor of several kinases that demonstrates in vitro activity primarily against FAK with activity against insulin-like growth factor-1 receptor (IGF1R) at higher concentrations. Methods: As FAK and IGF1R are potential molecular targets in glioblastomas, we examined the efficacy of TAE226 against human glioma cell lines and xenografts. Results: TAE226 inhibited the activating phosphorylation of FAK at submicromolar concentrations with residue specific preference. Downstream effectors (Akt and ERK) were inhibited at slightly higher concentrations. TAE226 demonstrated a concentration-dependent decrease in cellular proliferation with an associated G2 cell cycle arrest in multiple glioma cell lines, whereas TAE226 potently induced apoptosis in a concentration-dependent manner in only one of four cell lines tested. TAE226 also induced a concentration-dependent decrease in cellular adhesion, migration, and invasion. In preliminary animal studies, a limited course of orally administered TAE226 (100 mg/kg qd 5 days on/2 days off/5 days) was well tolerated with minimal weight loss. TAE226 induced a modest growth delay of human glioma xenografts grown in a subcutaneous location in athymic mice (3 to 4 days delay, p < 0.001). In addition, mice bearing orthotopic intracranial human glioma xenografts demonstrated a modest increase in median survival (3.5 days, p = 0.078). Despite the modest degree of the tumor responses, these results are superior to other low molecular weight inhibitors, such as epidermal growth factor receptor (EGFR) inhibitors. As glioma xenografts often grow without invasion, these results may underestimate the efficacy of targeting FAK as FAK plays a major role in tumor invasion. Conclusion: TAE226 demonstrates modest activity as monotherapy against malignant gliomas and warrants further investigation, potentially in combination with other therapies.

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Are adolescent boys with Klinefelter syndrome androgen deficient? A longitudinal study of Finnish 47,XXY boys

Testosterone (T)-substitution therapy is widely used in adult patients with Klinefelter syndrome (KS) to prevent symptoms and sequels of androgen deficiency, but it is currently unknown if adolescent boys with KS benefit from early T therapy. To evaluate the optimal age to start T substitution, we searched for signs of androgen deficiency in pubertal boys with KS. 14 nonmosaic 47,XXY boys, aged 10-13.9 y, were followed up for 4-37 mo with staging of puberty and frequent reproductive hormone measurements. Furthermore, indices reflecting androgen action (serum SHBG, leptin, and prostate-specific antigen (PSA) levels) were studied. Both onset and progression of puberty according to Tanner stages were normal in boys with KS. Consistently, serum T concentrations increased as expected and remained normal throughout follow-up. Changes in the indices of androgen action (decreases in serum SHBG and leptin, and increase in serum PSA concentrations) occurred normally, except that average leptin levels were higher in the boys with KS (KS boys 11.8 +/- 7.0 microg/L; controls 7.6 +/- 4.7 microg/L; p = 0.033). Despite normal T concentrations, the KS boys displayed from the age of 13 y elevated serum FSH and LH levels, and exaggerated gonadotropin responses to gonadotropin-releasing hormone. These data do not demonstrate an unequivocal androgen deficiency in adolescent boys with KS that would necessitate androgen supplementation therapy during early puberty.

Treatment with the aromatase inhibitor letrozole during adolescence increases near-final height in boys with constitutional delay of puberty

OBJECTIVE

We investigated whether inhibition of oestrogen biosynthesis with the aromatase inhibitor, letrozole, during adolescence improves near-final height in boys with constitutional delay of puberty.

PATIENTS AND METHODS

Seventeen boys with constitutional delay of puberty were randomized to receive testosterone (T) enanthate (1 mg/kg i.m.) every 4 weeks for 6 months in combination with placebo (Pl, n = 8), or the aromatase inhibitor letrozole (Lz, 2.5 mg/day orally) (n = 9), for 12 months. After treatment, patients were followed up until near-final height. Height discrepancy was calculated as near-final height minus mid-parental target height.

MEASUREMENTS

The primary end point was the difference in near-final height between the groups treated either with T + Pl or T + Lz. Secondarily, height discrepancy and gain in height standard deviation score (SDS) were analysed in both groups.

RESULTS

Boys treated with T + Lz reached a higher mean near-final height than did boys on T + Pl (175.8 vs. 169.1 cm, respectively, P = 0.04). In T + Lz-treated boys, mean near-final height did not differ from their mid-parental target height (175.8 vs. 177.1 cm, P = 0.38), whereas in T + Pl-treated boys, mean near-final height was lower than mid-parental target height (169.1 vs. 173.9 cm, P = 0.007). T + Lz-treated boys had a greater increment in height SDS over the pretreatment height SDS than T + Pl-treated boys (+1.4 SDS vs.+0.8 SDS, P = 0.03).

CONCLUSIONS

Our findings indicate that in adolescent boys an increase in adult height can be attained by use of aromatase inhibitors.

Pubertal upregulation of erythropoiesis in boys is determined primarily by androgen

OBJECTIVES

To study the relative roles of androgens and the growth hormone-insulin-like growth factor I (GH-IGF-I) system in the regulation of erythropoiesis in boys during puberty.

STUDY DESIGN

We treated 23 boys with constitutional delay of puberty with low-dose testosterone (T), in combination with either a potent aromatase inhibitor, letrozole (Lz; 2.5 mg/d), or placebo (P). The study design was randomized, double-blinded, and placebo-controlled between the treated groups. Treatment with T + Lz was associated with high T and low IGF-I concentrations, whereas treatment with T + P resulted in moderately increased T and high IGF-I concentrations.

RESULTS

The blood hemoglobin concentration increased by 1.6 g/dL in T + Lz-treated boys, despite their low IGF-I concentrations. The estimated red blood cell volume increased more in T + Lz-treated than in T + P-treated boys (349 vs 174 mL, respectively, P = .01). Serum T concentrations during the treatment period correlated with the 12-month increments in hemoglobin and red blood cell volume. The changes in blood hemoglobin concentration and RBC in T + Lz-treated boys were similar to those we observed in a population of normal adolescent boys in the late stages of puberty.

CONCLUSIONS

The pubertal increase in hemoglobin concentration in boys is related to direct androgen effects.

Serum androgen bioactivity in adolescence: a longitudinal study of boys with constitutional delay of puberty

We have examined the relationship between serum androgen bioactivity, as measured with a recombinant cell bioassay, and progression of puberty in 14 boys with constitutional delay of puberty. Six boys were followed up without treatment (control group), and eight boys received low-dose (1 mg/kg) testosterone enanthate im for 0-6 months together with an aromatase inhibitor, letrozole, 2.5 mg orally once a day for 0-12 months (treatment group). In the control group, serum androgen bioactivity increased during the course of puberty (P < 0.001). During 0-12 months of the study, the boys in the treatment group had higher androgen bioactivity levels (P < 0.05) and faster rate of pubic hair growth than the control boys (P < 0.05). Overall, the average serum androgen bioactivity during 12 months of follow-up correlated strongly with the concomitant changes in Tanner genital (r(S) = 0.89; n = 13; P < 0.005) and pubic hair stages (r(S) = 0.79; n = 13; P < 0.01). In conclusion, our results suggest that circulating androgen bioactivity mediates the tempo of pubertal maturation and that the combination of testosterone and letrozole given to boys with constitutional delay of puberty accelerates puberty.

Novel treatment of short stature with aromatase inhibitors

Estrogens have an essential role in the regulation of bone maturation and importantly in the closure of growth plates in both sexes. This prospective, randomized, placebo-controlled study was undertaken to evaluate whether suppression of estrogen synthesis in pubertal boys delays bone maturation and ultimately results in increased adult height. A total of 23 boys with constitutional delay of puberty (CDP) received a conventional, low-dose testosterone treatment for inducing progression of puberty. Eleven of these 23 boys were randomized to receive a specific and potent P450-aromatase inhibitor, letrozole, for suppression of estrogen action, and 12 boys were randomized to receive placebo. Estradiol concentrations in the letrozole-treated boys remained at the pretreatment level during the administration of letrozole, whereas the concentrations increased during the treatment with testosterone alone and during spontaneous progression of puberty. Testosterone concentrations increased in all groups, but during the letrozole treatment, the increase was more than fivefold higher than in the group treated with testosterone alone. The inhibition of estrogen synthesis delayed bone maturation. The slower bone maturation in the boys treated with testosterone and letrozole, despite higher androgen concentrations, than in the boys treated with testosterone indicate that estrogens are more important than androgens in regulation of bone maturation in pubertal boys. During the 18 months follow-up, an increase of 5.1 cm in predicted adult height was observed in the boys who received testosterone and letrozole, but no change was seen in the boys who received testosterone alone or in the untreated boys. This finding indicates that an increase in adult height can be attained in growing adolescent boys by inhibiting of estrogen action.

Effects of suppression of estrogen action by the p450 aromatase inhibitor letrozole on bone mineral density and bone turnover in pubertal boys

The essential role of estrogen (E) in regulation of developing peak bone mass in males was confirmed when young adult men were described who cannot respond to or produce E because of defective E receptor alpha or P-450 aromatase enzyme, respectively. These men had significantly reduced bone mineral density (BMD) despite normal or supranormal androgen concentrations, and E administration improved BMD in the men with aromatase deficiency, whereas testosterone (T) was ineffective. Because new P450 aromatase inhibitors may prove to be potential drugs in various growth disorders, the effect of suppression of E action on developing peak bone mass has to be closely evaluated. In this study, we explored the effects of suppression of E synthesis on bone metabolism in pubertal boys. A total of 23 boys with constitutional delay of puberty were randomized to receive T and placebo or T and a specific and potent P450 aromatase inhibitor, letrozole. We determined BMD in the lumbar spine and the femoral neck. Bone resorption was studied by measuring the serum concentration of cross-linked carboxyterminal telopeptide of type I collagen by two different methods (CTx and ICTP), and bone formation by determining the serum concentrations of carboxyterminal propeptide of type I procollagen (PICP), osteocalcin, and alkaline phosphatase. We demonstrated previously that, during treatment with T and placebo, the concentrations of androgens and E increased. During treatment with T and letrozole, the E concentrations remained at the pretreatment level, but the androgen concentrations increased; the increase in the T concentration was more than 5-fold higher than during treatment with T and placebo. We did not observe any significant differences in the changes in bone mineral content, BMD, or bone mineral apparent density, an estimate of true volumetric BMD, between the treated groups. Lumbar spine bone mineral apparent density increased in both treated groups; but in the T- plus letrozole-treated group, the increase was statistically significant only 6 months after discontinuation of letrozole treatment. All bone resorption and formation markers increased during treatment with T and placebo. During treatment with T plus letrozole, CTx, PICP, and osteocalcin remained unchanged, whereas ICTP and alkaline phosphatase increased. Thus, 1-yr treatment with this new P450 aromatase inhibitor in pubertal boys is unlikely to be associated with any major harmful effect on developing peak bone mass. However, to convincingly exclude such effects, particularly rare or minor ones, will require a study with a larger sample size; and thus, close follow-up of bone metabolism during treatment with P450 aromatase inhibitors is still warranted.

Novel treatment of delayed male puberty with aromatase inhibitors

BACKGROUND

As the evidence for the role of oestrogens in epiphyseal closure appears unequivocal, we hypothesized that boys with constitutional delay of puberty would attain greater adult height if oestrogen action was suppressed.

METHODS

We conducted a randomized, double-blind, placebo-controlled study in which we treated boys with constitutional delay of puberty with testosterone plus placebo or testosterone plus a potent fourth-generation aromatase inhibitor, letrozole.

FINDINGS

Letrozole effectively inhibited oestrogen synthesis. The 17beta-oestradiol concentrations increased in the untreated group and in the testosterone/placebo-treated group, but in the testosterone/letrozole-treated group no such increase was observed until letrozole treatment was discontinued. Testosterone concentrations were threefold higher in the testosterone/letrozole-treated group than in the other groups. Within 18 months, bone age had advanced by 1.1 +/- 0.3 years in the untreated group and by 1.7 +/- 0.3 years in the testosterone/placebo-treated group, but only by 0.9 +/- 0.2 years in the testosterone/letrozole-treated group (p = 0.02 between treatment groups). Predicted adult height did not change significantly in the untreated group and in the testosterone/placebo-treated group, whereas in the testosterone/letrozole-treated group the increase was 5.1 +/- 1.2 cm (p = 0.004).

CONCLUSIONS

Our findings suggest that, if oestrogen action is inhibited in growing adolescents, adult height will increase. This observation provides a rationale for studies aimed at delaying bone maturation in several growth disorders.

The role of sex steroids in the regulation of insulin sensitivity and serum lipid concentrations during male puberty: a prospective study with a P450-aromatase inhibitor

OBJECTIVE

Our purpose was to study the sex steroid-mediated changes in serum insulin and lipid concentrations in boys during puberty.

DESIGN AND METHODS

We treated boys with constitutional delay of puberty either with testosterone plus placebo or with testosterone plus an aromatase inhibitor, letrozole, which inhibits the conversion of androgens to oestrogens. We demonstrated previously that during treatment with testosterone plus letrozole the increase in testosterone concentration was more than 5-fold higher than during treatment with testosterone plus placebo. The concentrations of 17beta-oestradiol, IGF-I and IGF-binding protein-3 increased during testosterone-plus-placebo treatment, but during testosterone-plus-letrozole treatment the concentrations remained unchanged. These divergent changes in the two groups enabled us to study the effects of sex steroids and GH on insulin sensitivity and lipid concentrations.

RESULTS

The insulin concentration in the testosterone-plus-placebo-treated group did not change. In contrast, in the testosterone-plus-letrozole-treated group, the concentration decreased during letrozole treatment, indicating improved insulin sensitivity. Changes in insulin and IGF-I concentrations within 12 and 18 months were correlated. In the testosterone-plus-placebo-treated group, the high-density lipoprotein cholesterol concentration did not change but in the testosterone-plus-letrozole-treated group the concentration decreased. The concentrations of low-density lipoprotein cholesterol (LDL-cholesterol) and triglycerides did not change in either of the groups.

CONCLUSIONS

The findings indicate that androgens do not directly alter insulin sensitivity in boys during puberty. In contrast, the observations suggest tight regulation of glucose--insulin homeostasis by GH in boys at this stage. Furthermore, our findings indicate that sex steroids do not significantly participate in the regulation of serum concentrations of LDL-cholesterol or triglycerides in boys during early and mid-puberty.

Inhibition of P450 aromatase enhances gonadotropin secretion in early and midpubertal boys: evidence for a pituitary site of action of endogenous E

In early pubertal boys, E concentrations are very low. We studied the role and site of action of endogenous E in the regulation of gonadotropin secretion in early and midpubertal boys by inhibiting the action of E with a potent and specific P450 aromatase inhibitor, letrozole. A total of 35 boys who were referred to us because of suspicion of delayed puberty were included in the study. The boys were in either early or midpuberty, and they composed 3 groups: 10 boys did not receive any treatment, 12 boys received T alone, and 13 boys received T and letrozole. In the untreated group during the 5-month follow-up, no changes were observed in 17beta-E2, T, basal gonadotropin, or inhibin B concentrations or in the GnRH-induced gonadotropin responses. In the T-treated group during the 5-month treatment, the T concentration increased by 55% (P < 0.05), and the 17beta-E2 concentration increased by 130% (P < 0.02). Concurrently, basal gonadotropin concentrations were suppressed, but the GnRH-induced gonadotropin responses and the inhibin B concentration remained unchanged. In the T- plus letrozole-treated group during the 5-month treatment, an increase in T concentration of 606% was observed (P < 0.001), but the 17beta-E2 concentration remained unchanged. The changes in the 17beta-E2 concentration within 5 months in the untreated and the T- plus letrozole-treated groups were different (P < 0.02), indicating significant inhibition of endogenous E synthesis during letrozole treatment. During the T plus letrozole treatment, basal gonadotropin concentration, the GnRH-induced LH response, and inhibin B concentration increased, and the GnRH-induced FSH response did not change significantly. Serum nocturnal gonadotropin pulses were determined in 5 boys treated with T and in 5 boys treated with T plus letrozole. In the T- plus letrozole-treated group, the nocturnal LH pulse amplitude increased, and the LH pulse frequency and interpulse interval remained unchanged. In conclusion, in early and midpubertal boys, suppression of the action of E by the P450 aromatase inhibitor increased LH concentration, LH pulse amplitude, and the GnRH-induced LH response, which indicates that in boys during early and midpuberty, endogenous E regulates LH secretion at the site of the pituitary.

A specific aromatase inhibitor and potential increase in adult height in boys with delayed puberty: a randomised controlled trial

BACKGROUND

The role of oestrogens in the closure of growth plates in both sexes is unequivocal. We postulated that inhibition of oestrogen synthesis in boys with delayed puberty would delay maturation of the growth plates and ultimately result in increased adult height.

METHODS

We did a randomised, double-blind, placebo-controlled study in which we treated boys with constitutional delay of puberty with testosterone and placebo, or testosterone and letrozole. Boys who decided to wait for the spontaneous progression of puberty without medical intervention composed the untreated group.

FINDINGS

Letrozole effectively inhibited oestrogen synthesis and delayed bone maturation. Progression of bone maturation was slower in the letrozole group than in the placebo group. In 18 months, bone age had advanced 1.1 (SD 0.8) years in the untreated group and 1.7 (0.9) years in the group treated with testosterone and placebo, but only 0.9 (0.6) years in the letrozole group (p=0.03 between the treatment groups). Predicted adult height did not change significantly in the untreated group and in the placebo group, whereas in the group treated with letrozole the increase was 5.1 (3.7) cm (p=0.004).

INTERPRETATIONS

Our findings suggest that if oestrogen action is inhibited in growing adolescents, adult height will increase. This finding provides a rationale for studies that aim to delay bone maturation in several growth disorders.

Novel assay for determination of androgen bioactivity in human serum

We have developed a mammalian cell (COS-1) bioassay, which can measure androgen bioactivity directly from a small amount (10 microL) of human serum. The recombinant assay is based on androgen-dependent interaction between the ligand-binding domain and the N-terminal region of the androgen receptor (AR), which were fused to Gal4 DNA-binding domain of Saccharomyces cerevisiae and transcriptional activation domain of herpes simplex VP16 protein, respectively. The interaction is amplified by coexpression of AR-interacting protein 3 in the cells. The reporter plasmid contains 5 Gal4-binding sites upstream of the luciferase gene; luciferase activity in cell lysates is derived from androgen bioactivity in human serum. Saturating concentration of testosterone in FCS induced more than 700-fold induction in relative luciferase activity. The sensitivity was less than 1.0 nmol/L testosterone in FCS. The intra- and interassay coefficients of variation were 8.3% and 21%, respectively. Interaction between the AR termini was blocked by nonsteroidal antiandrogens, and the assay exhibited minimal cross-reactivity with 17 beta-estradiol. Serum androgen bioactivity was studied in 23 boys (13.9--16.8 yr old) with constitutional delay of puberty and in 9 prepubertal boys with cryptorchidism (1.0--6.4 yr old). Androgen bioactivity was detectable in 15 boys with constitutional delay of puberty and in all boys with cryptorchidism during treatment with human CG (range, 1.0-14.5 nmol/L testosterone equivalents). Serum androgen bioactivity measured by the bioassay correlated strongly with serum testosterone concentration (r = 0.93, P < 0.0001, n = 22) but not to 5 alpha-dihydrotestosterone, dehydroepiandrosterone, or androstenedione levels. We conclude that our novel bioassay enables quantitation of mammalian cell response to bioactive androgens in human serum, even in pediatric patients with relatively low androgen levels.

Treatment of delayed male puberty: efficacy of aromatase inhibition

We hypothesized that inhibition of estrogen synthesis would delay maturation of the growth plates and ultimately result in increased adult height in boys with delayed puberty. We conducted a randomized, double-blind, placebo-controlled study in which we treated boys with constitutional delay of puberty with testosterone plus placebo (testosterone-placebo) or with testosterone plus letrozole (testosterone-letrozole). Letrozole effectively inhibited estrogen synthesis: 17beta-estradiol concentrations increased in the testosterone-placebo group, but in the testosterone-letrozole group, no such increase was observed until letrozole treatment was discontinued. After 1.5 years, bone age had advanced by 1.7 +/- 0.3 years in the testosterone-placebo group, but by only 0.9 +/- 0.2 years in the testosterone-letrozole group (p = 0.02). Predicted adult height did not change significantly in the testosterone-placebo group, whereas in the testosterone-letrozole group the increase was 5.1 +/- 1.2 cm (p = 0.004). Our findings suggest that, if estrogen action is inhibited in growing adolescents, adult height will increase. This observation provides a rationale for studies aimed at delaying bone maturation in several growth disorders.