Bone mass and mineral metabolism in Klinefelter's syndrome

The complications of male hypogonadism: is it just a matter of low testosterone?

The history of diagnosing hypogonadism and hypotestosteronemia shows us the many steps that were necessary to achieve our current knowledge and the ability to improve these patients' well-being. Moreover, so far, criteria for diagnosing hypotestosteronemia varies according to the underlying condition, and according to the consensus or guideline adopted. Furthermore, besides the many signs and symptoms, there are several complications associated with low testosterone levels such as osteoporosis, metabolic alterations, as well as cardiovascular disorders. However, data are often conflicting regarding the severity, timing or even the real clinical relevance of these complications, although these studies often lack essential information such as gonadotropin levels or the underlying cause of hypogonadism. The present review focus on the complications of male hypogonadism according to the cause of testosterone deficiency, highlighting the lack of information found in many studies investigating its effects. We thereby stress the necessity to always perform a complete evaluation of the type of hypogonadism (including at least gonadotropins and secondary causes) when investigating the effects of low testosterone levels.

Klinefelter Bone Microarchitecture Evolution with Testosterone Replacement Therapy

Klinefelter Syndrome (KS) patients, defined by a 47 XXY karyotype, have increased risk of fragility fractures. We have assessed bone microarchitecture by high resolution peripheral quantitative CT (HR-pQCT) at the radius and tibia in young KS patients, naïve from testosterone replacement therapy (TRT). Areal bone mineral density (BMD) and body composition were assessed by dual X-ray absorptiometry (DXA). Total testosterone (tT) was measured at baseline. Bone measurements have been repeated after 30 months of TRT. We enrolled 24 KS patients and 72 age-matched controls. KS patients were (mean ± SD) 23.7 ± 7.8 year-old. KS patients had significantly lower relative appendicular lean mass index (RALM) and lower aBMD at spine and hip than controls. Ten patients (42%) had low tT level (≤ 10.4 nmol/L). At baseline, we observed at radius a marked cortical (Ct) impairment reflected by lower Ct.area, Ct.perimeter, and Ct.vBMD than controls. At tibia, in addition to cortical fragility, we also found significant alterations of trabecular (Tb) compartment with lower trabecular bone volume (BV/TV) and Tb.vBMD as compared to controls. After 30 months of TRT, 18 (75%) KS patients were reassessed. Spine aBMD and RALM significantly increased. At radius, both cortical (Ct.Pm, Ct.Ar, Ct.vBMD, Ct.Th) and trabecular (Tb.vBMD) parameters significantly improved. At tibia, the improvement was found only in the cortical compartment. Young TRT naïve KS patients have inadequate bone microarchitecture at both the radius and tibia, which can improve on TRT.

Androgens and Androgen Receptor Actions on Bone Health and Disease: From Androgen Deficiency to Androgen Therapy

Androgens are not only essential for bone development but for the maintenance of bone mass. Therefore, conditions with androgen deficiency, such as male hypogonadism, androgen-insensitive syndromes, and prostate cancer with androgen deprivation therapy are strongly associated with bone loss and increased fracture risk. Here we summarize the skeletal effects of androgens—androgen receptors (AR) actions based on in vitro and in vivo studies from animals and humans, and discuss bone loss due to androgens/AR deficiency to clarify the molecular basis for the anabolic action of androgens and AR in bone homeostasis and unravel the functions of androgen/AR signaling in healthy and disease states. Moreover, we provide evidence for the skeletal benefits of androgen therapy and elucidate why androgens are more beneficial than male sexual hormones, highlighting their therapeutic potential as osteoanabolic steroids in improving bone fracture repair. Finally, the application of selective androgen receptor modulators may provide new approaches for the treatment of osteoporosis and fractures as well as building stronger bones in diseases dependent on androgens/AR status.

Relative hyperestrogenism in Klinefelter Syndrome: results from a meta-analysis

OBJECTIVE

Klinefelter Syndrome (KS) is classically described as characterized by hyperestrogenism, although solid evidence is lacking. This study aims to test the hypothesis that men with KS have higher serum estradiol than normal controls.

DESIGN

Meta-analysis of all studies extracted by MEDLINE from 1942 to 31 January 2018. All studies reporting serum estradiol measurement were considered, among them only case-control studies were included in the meta-analysis.

METHODS

Meta-analysis was conducted according to the PRISMA statement using RevMan.

RESULTS

Out of 4120 articles, 23 case-control studies, 14 case series, and 19 case reports reported data on serum estradiol. A total of 707 KS and 1019 controls were included in the meta-analysis. Serum estradiol was slightly, but significantly higher in KS than controls (mean difference 4.25 pg/mL; CI: 0.41, 8.10 pg/mL; p = 0.030). This difference was lost considering only studies using estradiol assays with good accuracy (5.48 pg/mL, CI: -2.11, 13.07 pg/mL; p = 0.160). Serum testosterone and estradiol/testosterone ratio were significantly lower and higher in KS than controls, respectively. Data from KS case series and case reports confirmed that serum estradiol is within the normal ranges.

CONCLUSIONS

Serum estradiol is not increased in KS although slightly higher than controls. However, the meta-analysis that included only studies using a serum estradiol assay with good accuracy showed no difference in serum estradiol between KS and controls. The traditional belief that KS is associated with elevated serum estradiol should be reconsidered. This meta-analysis shows that men with KS have relative hyperestrogenism (increased estradiol/testosterone ratio) compared to controls.

Stanozolol-soaked grafts enhance new bone formation in rat calvarial critical-size defects

Androgen hormones play a significant role in regulating bone morphogenesis and in maintaining bone homeostasis throughout life. This study aimed to investigate the local effects of the non-aromatizable androgen stanozolol (ST) on bone regeneration in rats. Bilateral critical-size defects were created in the parietal bone of 26 male Wistar rats: the defect on one side was filled with a deproteinized bovine bone scaffold (DBB) soaked in ST solution (test) and the contralateral with DBB alone (control). Samples were collected at one month and three months. Histomorphometry revealed a significantly higher new bone formation (NB) (24.41% ± 4.14% versus 15.01% ± 2.43%, p < 0.05) and mineral apposition rate (MAR) (9.20 μm/day ± 0.37 versus 6.50 μm/day ± 1.09, p < 0.05) in the test versus control group at one month. Accordingly, real time-polymerase chain reaction revealed a consistently higher Runx2 expression in test samples (fold change test/control: 4.50 ± 1.17, p ≤ 0.05). No morphometrical differences between groups were detected at three months (p > 0.05). However, test samples were characterized by an increase in blood capillary density from one month (11.43 n mm^-2 ± 2.01) to three months (28.26 n mm^-2 ± 5.62), providing evidence of a vital remodeling tissue. Control samples presented a decrease of anti-Osterix (SP7)/anti-osteocalcin (BGLAP) (3.9 n mm^-2 ± 0.32 versus 1.01 n mm^-2 ± 0.20) and alkaline phosphatase (ALP) (12.14 n mm^-2 ± 6.29 versus 6.29 n mm^-2 ± 2.73) immunohistochemical-positive elements, which was suggestive of a stabilized healing phase. Based on these observations, local ST administration boosted bone regeneration in rat calvarial critical-size defects at one month. This study showed the potential of local steroid delivery in bone regeneration.

Role of vitamin D levels and vitamin D supplementation on bone mineral density in Klinefelter syndrome

This manuscript describes the role of low vitamin D in bone metabolism of Klinefelter subjects. Low vitamin D is frequent in this condition and seems to be more important than testosterone in inducing low bone mineral density (BMD) and osteoporosis. Supplementation with vitamin D restores BMD after 2 years of treatment, whereas testosterone alone seems to be ineffective.

INTRODUCTION

Decreased bone mineral density (BMD) in Klinefelter syndrome (KS) is frequent, and it has been traditionally related to low testosterone (T) levels. However, low BMD can be observed also in patients with normal T levels and T replacement therapy does not necessarily increase bone mass in these patients. Nothing is known about vitamin D levels and supplementation in KS. In this study, we determine vitamin D status and bone mass in KS subjects and compare the efficacy of T therapy and vitamin D supplementation on BMD.

METHODS

A total of 127 non-mosaic KS patients and 60 age-matched male controls were evaluated with reproductive hormones, 25-hydroxyvitamin D, PTH, and bone densitometry by dual-energy X-ray absorptiometry (DEXA). Patients with hypogonadism and/or 25-hydroxyvitamin D deficiency were treated with T-gel 2% and/or calcifediol and re-evaluated after 24 months of treatment.

RESULTS

25-hydroxyvitamin D levels were significantly lower in KS patients with respect to controls, and they had significantly lower lumbar and femoral BMD. The percentage of osteopenia/osteoporosis in subjects with 25-hydroxyvitamin D deficiency was higher with respect to subjects with normal 25-hydroxyvitamin D and was not related to the presence/absence of low T levels. Subjects treated with calcifediol or T + calcifediol had a significant increase in lumbar BMD after treatment. No difference was found in T-treated group.

CONCLUSIONS

These data highlight that low 25-hydroxyvitamin D levels seem to have a more critical role than low T levels in inducing low BMD in KS subjects. Furthermore, vitamin D supplementation seems to be more effective than T replacement therapy alone in increasing BMD.

Bone geometry, volumetric density, microarchitecture, and estimated bone strength assessed by HR-pQCT in Klinefelter syndrome

Although the expected skeletal manifestations of testosterone deficiency in Klinefelter's syndrome (KS) are osteopenia and osteoporosis, the structural basis for this is unclear. The aim of this study was to assess bone geometry, volumetric bone mineral density (vBMD), microarchitecture, and estimated bone strength using high-resolution peripheral quantitative computed tomography (HR-pQCT) in patients with KS. Thirty-one patients with KS confirmed by lymphocyte chromosome karyotyping aged 35.8 ± 8.2 years were recruited consecutively from a KS outpatient clinic and matched with respect to age and height with 31 healthy subjects aged 35.9 ± 8.2 years. Dual-energy X-ray absorptiometry (DXA) and HR-pQCT were performed in all participants, and blood samples were analyzed for hormonal status and bone biomarkers in KS patients. Twenty-one KS patients were on long-term testosterone-replacement therapy. In weight-adjusted models, HR-pQCT revealed a significantly lower cortical area (p < 0.01), total and trabecular vBMD (p = 0.02 and p = 0.04), trabecular bone volume fraction (p = 0.04), trabecular number (p = 0.05), and estimates of bone strength, whereas trabecular spacing was higher (p = 0.03) at the tibia in KS patients. In addition, cortical thickness was significantly reduced, both at the radius and tibia (both p < 0.01). There were no significant differences in indices of bone structure, estimated bone strength, or bone biomarkers in KS patients with and without testosterone therapy. This study showed that KS patients had lower total vBMD and a compromised trabecular compartment with a reduced trabecular density and bone volume fraction at the tibia. The compromised trabecular network integrity attributable to a lower trabecular number with relative preservation of trabecular thickness is similar to the picture found in women with aging. KS patients also displayed a reduced cortical area and thickness at the tibia, which in combination with the trabecular deficits, compromised estimated bone strength at this site.

The role of hypogonadism in Klinefelter syndrome

Klinefelter syndrome (KS) (47, XXY) is the most abundant sex-chromosome disorder, and is a common cause of infertility and hypogonadism in men. Most men with KS go through life without knowing the diagnosis, as only 25% are diagnosed and only a few of these before puberty. Apart from hypogonadism and azoospermia, most men with KS suffer from some degree of learning disability and may have various kinds of psychiatric problems. The effects of long-term hypogonadism may be diffi cult to discern from the gene dose effect of the extra X-chromosome. Whatever the cause, alterations in body composition, with more fat and less muscle mass and diminished bone mineral mass, as well as increased risk of metabolic consequences, such as type 2 diabetes and the metabolic syndrome are all common in KS. These findings should be a concern as they are not simply laboratory findings; epidemiological studies in KS populations show an increased risk of both hospitalization and death from various diseases. Testosterone treatment should be offered to KS patients from early puberty, to secure a proper masculine development, nonetheless the evidence is weak or nonexisting, since no randomized controlled trials have ever been published. Here, we will review the current knowledge of hypogonadism in KS and the rationale for testosterone treatment and try to give our best recommendations for surveillance of this rather common, but often ignored, syndrome.

Bone density and risk of osteoporosis in Klinefelter syndrome

Different mechanisms in Klinefelter syndrome contribute to reduced bone mass and osteoporosis, which have a precocious onset and are detected in up to 40% of patients, irrespectively of testosterone levels. Androgen receptor, X chromosome inactivation and INSL3 levels are hypothesized to cooperate with and modulate the effect of testosterone on the bone.

CONCLUSION

New perspectives on genetic topics are opening exciting areas of research on the pathophysiology of reduced bone mass in Klinefelter patients.

Bone mineral density in Klinefelter syndrome is reduced and primarily determined by muscle strength and resorptive markers, but not directly by testosterone

SUMMARY

Klinefelter syndrome (KS) patients have lower bone mineral density (BMD) at the spine, hip and forearm compared to healthy subjects, but frank osteoporosis is not common. Muscle strength and bone markers predicted BMD but KS itself and serum testosterone did not. Low vitamin D and high PTH were frequent among KS.

INTRODUCTION

The long-term consequence of KS on bone health is not well described. The objective of this study is to investigate the regional BMD and its determinants in KS.

METHODS

This is a cross-sectional study. BMD at the spine, hip and forearm are measured by DXA and correlated to biochemical markers of bone turnover, vitamin D metabolites, PTH, sex hormones, growth factors as well as muscle strength and anthropometric measures. The setting is at a university clinical research centre. The study involves 70 adult KS patients and 71 age-matched healthy subjects.

RESULTS

In KS, BMD was universally lowered in all regions. Markers of bone formation or bone resorption were not altered in KS, but 25-OH-Dvitamin was lower (55 vs. 82 nmol/L, p < 0.0001) than in healthy subjects. Significantly more KS patients had low BMD (Z-scores below -2) at the forearm (15 KS vs. two healthy subjects, p = 0.001) but not at the spine or hip. Muscle strength (bicep and quadriceps) was lower among KS patients. Multivariate analysis revealed that muscle strength, treatment with testosterone (ever/never), age at diagnosis, SHBG, bone-specific alkaline phosphatase and 1CTP were all independent predictors of BMD, but androgens was not.

CONCLUSIONS

KS patients had lower BMD at the spine, hip and forearm compared to age-matched healthy subjects, but frank osteoporosis was not common. Muscle strength, previous history of testosterone treatment, age at diagnosis and bone markers were predictors of BMD, but testosterone was not. Signs of secondary hyperparathyroidism were present among KS. Dietary intake of vitamin D or sun exposure may be lower in KS patients.

Bone mass in subjects with Klinefelter syndrome: role of testosterone levels and androgen receptor gene CAG polymorphism

CONTEXT

Klinefelter syndrome (KS) is a chromosomal alteration characterized by supernumerary X-chromosome(s), primary hypogonadism, decreased pubertal peak bone mineral density (BMD), and accelerated bone loss during adulthood. Decreased bone mass has been traditionally related to low testosterone levels. However, testosterone replacement therapy does not necessarily increase bone mass in these patients, and low BMD can be observed also in patients with normal testosterone levels. The androgen receptor (AR) gene CAG polymorphism seems to modulate the sensitivity to testosterone and previous studies have related it to some clinical aspects of KS, to include BMD, gynecomastia, testes and prostate volume, and hemoglobin concentration.

OBJECTIVE

To analyze the relation between bone mass, testosterone, and AR CAG polymorphism in men with KS.

DESIGN

Cross-sectional cohort study.

SETTING

University department.

PATIENTS

One hundred twelve consecutive treatment-naïve 47,XXY Klinefelter patients (mean age 33.5 ± 4.7 yr) and 51 age-matched normal male controls.

MAIN OUTCOME MEASURES

Dual-energy x-ray absorptiometry, CAG repeat length polymorphism, X-chromosome inactivation, and testosterone levels.

RESULTS

Forty-nine of 112 KS subjects (42.5%) had low bone mass (osteopenia or osteoporosis). Lumbar and/or femoral T-scores were lower in KS patients compared with controls. No significant relationship was observed between testosterone levels and bone parameters, and the prevalence of osteopenia/osteoporosis was similar in subjects with normal and low testosterone levels (43.7% and 40.5%, respectively). The mean CAG repeat length calculated after X-chromosome inactivation analysis showed no differences between patients with normal and low bone mass.

CONCLUSIONS

Testosterone levels and AR CAG polymorphism are not associated with bone mass phenotype in KS.

Perinatal testosterone surge is required for normal adult bone size but not for normal bone remodeling

Although testosterone (T) has striking effects on mature skeletal size and structure, it is not clear whether this depends exclusively on adult circulating levels of T or whether additional early-life factors also play a role. We have compared the androgen-deficient hypogonadal (hpg) mutant mouse with intact, orchidectomized, and T-treated non-hpg mice to determine relative contributions of adult and perinatal T to bone growth and development. At 3 wk of age, although trabecular and cortical bone structure was normal, bone turnover was significantly altered in hpg male mice; osteoid volume (OV/BV) and osteoblast surface (ObS/BS) were significantly lower and osteoclast surface (OcS/BS) significantly higher in hpg mice compared with age-matched non-hpg mice, pointing to a role for the perinatal T surge in determining bone turnover levels before sexual maturity. At 9 wk of age, the hpg bone phenotype mimicked closely that of age-matched non-hpg mice that had been orchidectomized at 3 wk of age, including low trabecular bone mass and high bone turnover. These bone phenotypes of hpg and orchidectomized non-hpg mice were all prevented by replacement doses of T or dihydrotestosterone (DHT), suggesting that these are determined by adult sex steroid hormones. In contrast, a short bone phenotype that could not be prevented by T or DHT treatment was observed in 9-wk-old hpg mice yet not in intact or castrated non-hpg mice. These data suggest a role for the perinatal T surge in determining adult bone length and confirms that adult circulating T determines adult bone density.

Osteoporosis in children and adolescents: etiology and management

Bone mass increases progressively during childhood, but mainly during adolescence when approximately 40% of total bone mass is accumulated. Peak bone mass is reached in late adolescence, and is a well recognised risk factor for osteoporosis later in life. Thus, increasing peak bone mass can prevent osteoporosis. The critical interpretation of bone mass measurements is a crucial factor for the diagnosis of osteopenia/osteoporosis in children and adolescents. To date, there are insufficient data to formally define osteopenia/osteoporosis in this patient group, and the guidelines used for adult patients are not applicable. In males and females aged <20 years the terminology 'low bone density for chronologic age' may be used if the Z-score is less than -2. For children and adolescents, this terminology is more appropriate than osteopenia/osteoporosis. Moreover, the T-score should not be used in children and adolescents. Many disorders, by various mechanisms, may affect the acquisition of bone mass during childhood and adolescence. Indeed, the number of disorders that have been identified as affecting bone mass in this age group is increasing as a consequence of the wide use of bone mass measurements. The increased survival of children and adolescents with chronic diseases or malignancies, as well as the use of some treatment regimens has resulted in an increase in the incidence of reduced bone mass in this age group. Experience in treating the various disorders associated with osteoporosis in childhood is limited at present. The first approach to osteoporosis management in children and adolescents should be aimed at treating the underlying disease. The use of bisphosphonates in children and adolescents with osteoporosis is increasing and their positive effect in improving bone mineral density is encouraging. Osteoporosis prevention is a key factor and it should begin in childhood. Pediatricians should have a fundamental role in the prevention of osteoporosis, suggesting strategies to achieve an optimal peak bone mass.

Androgens and bone

Loss of estrogens or androgens increases the rate of bone remodeling by removing restraining effects on osteoblastogenesis and osteoclastogenesis, and also causes a focal imbalance between resorption and formation by prolonging the lifespan of osteoclasts and shortening the lifespan of osteoblasts. Conversely, androgens, as well as estrogens, maintain cancellous bone mass and integrity, regardless of age or sex. Although androgens, via the androgen receptor (AR), and estrogens, via the estrogen receptors (ERs), can exert these effects, their relative contribution remains uncertain. Recent studies suggest that androgen action on cancellous bone depends on (local) aromatization of androgens into estrogens. However, at least in rodents, androgen action on cancellous bone can be directly mediated via AR activation, even in the absence of ERs. Androgens also increase cortical bone size via stimulation of both longitudinal and radial growth. First, androgens, like estrogens, have a biphasic effect on endochondral bone formation: at the start of puberty, sex steroids stimulate endochondral bone formation, whereas they induce epiphyseal closure at the end of puberty. Androgen action on the growth plate is, however, clearly mediated via aromatization in estrogens and interaction with ERalpha. Androgens increase radial growth, whereas estrogens decrease periosteal bone formation. This effect of androgens may be important because bone strength in males seems to be determined by relatively higher periosteal bone formation and, therefore, greater bone dimensions, relative to muscle mass at older age. Experiments in mice again suggest that both the AR and ERalpha pathways are involved in androgen action on radial bone growth. ERbeta may mediate growth-limiting effects of estrogens in the female but does not seem to be involved in the regulation of bone size in males. In conclusion, androgens may protect men against osteoporosis via maintenance of cancellous bone mass and expansion of cortical bone. Such androgen action on bone is mediated by the AR and ERalpha.

Bone mineral density in early-onset hypogonadism and the effect of hormonal replacement

Hypogonadism is associated with reduction of bone mineral density (BMD), especially if sex steroid deficiency occurs early in life. In this situation, the effect of hormonal replacement therapy on bone mass is controversial. We evaluated the BMD through dual-energy X-ray absorptiometry (DXA) in patients with genetically determined hypogonadism or hypogonadism acquired in adulthood. The results of the BMD of patients never treated (pretreatment) or under treatment were compared with population standards and were submitted to pair analysis. Thirty-three patients were evaluated: group 1: BMD evaluated pretreatment (24); group 2: BMD evaluated under treatment (21); group 3: BMD evaluated pretreatment and under treatment (12). In group 1, there was a significant reduction of bone mass in all regions, with no gender differences. In patients with concomitant growth hormone (GH) deficiency, the total body (-3.60) and lumbar spine (-4.10) BMDs were significantly reduced compared to patients without associated GH deficiency (-2.37 and -2.35, respectively). In group 2, a significant reduction of bone mass was detected in all regions. In group 3, the patients showed statistically significant improvement in BMD with hormonal replacement therapy in all regions in both sexes. We conclude that the early onset of hypogonadism reduces the BMD significantly. This effect is increased when there is associated GH deficiency. Gonadal steroid replacement therapy increases the BMD in all bone regions, and the increase is similar in both sexes. However, although hormone replacement improves bone mass, it still remains significantly lower in comparision with population standards.

Bone mass, gonadal function and biochemical assessment in young men with trisomy 21

OBJECTIVE

The objective of the study was to find out whether biochemical and hormonal profile of sexual function and mineral metabolism are related to low bone mass in young men with Down syndrome.

STUDY DESIGN

Eleven young men with trisomy 21 (mean age 26.45 years) and 12 healthy university students of similar age, participated in the study. The bone mineral density (BMD) of the lumbar vertebrae was measured in posteroanterior (PA) projection. Sexual development was assessed by clinical examination. The levels of follicle stimulating hormone (FSH), luteinizing hormone (LH), testosterone, dehydroepiandrosterone sulfate (DHEA-S), 17-OH progesterone and parathormone (PTH) were measured accordingly by radioimmunoassay. Serum calcium (Ca) and phosphate (P) as well as fasting urinary Ca and hydroxyproline (OHP) were also measured.

RESULTS

BMD in DS patients was significantly lower (P<0.001) compared to their control counterparts. No significant differences were observed in mean concentrations of FSH, testosterone and DHEA-S, while LH and 17-OH progesterone levels were significantly higher in DS compared to control group (P<0.01 and <0.05, respectively). Serum Ca and P and urine Ca/Creat ratio did not differ between groups. OHP/Creat ratio was significantly higher in DS patients. PTH levels were extremely low (1pmol/l) in two patients.

CONCLUSIONS

The findings of this study show decreased bone mass in subjects with DS. Factors, possibly related to low bone mass, are some degree of hypogonadim, hypotonia, low muscular strength and immobility. The findings suggest further research on the biochemistry and endocrinology of bone metabolism in patients with trisomy 21.

Bone mineral density and bone markers in hypogonadotropic and hypergonadotropic hypogonadal men after prolonged testosterone treatment

After prolonged treatment (76.4+/-10 and 70.1+/-12.3 months, respectively) (mean+/-SE) with testosterone enanthate (250 mg i.m. every 3 weeks), bone mineral density (BMD) and bone metabolism were evaluated in 12 patients (aged 29.3+/-1.4 yr) affected by idiopathic hypogonadotropic hypogonadism (IHH), in 8 patients (29.6+/-2.6 yr) affected by Klinefelter's syndrome (KS), and in 10 healthy men (30.6+/-1.7 yr) matched according to age and BMI. Spinal BMD in IHH was significantly lower than in controls (0.804+/-0.04 vs 1.080+/-0.01 g/cm2; p<0.001), while there was no difference in neck BMD (0.850+/-0.01 vs 0.948+/-0.02 g/cm2). Neither spinal (0.978+/-0.05 g/cm2) nor neck (0.892+/-0.03 g/cm2) BMD in KS were significantly different from controls. Six IHH and one KS subjects were osteoporotic, while 6 IHH and 2 KS subjects were osteopenic. A significant inverse correlation was found between spinal BMD and age at the treatment onset in IHH (r=-0.726, p=0.007). In IHH there were significant increases in bone formation (alkaline phosphatase=318.3+/-33.9 vs 205.4+/-20.0 IU/l; osteocalcin=13.44+/-1.44 vs 8.57+/-0.94 ng/ml; p<0.05) and in bone resorption (urinary cross-linked N-telopeptides of type I collagen=149.1+/-32.3 vs 47.07+/-8.4 nmol bone collagen equivalents/mmol creatinine; p<0.05) compared to controls, while such differences were not present in KS. Our results outline the importance of BMD evaluation in all hypogonadal males. Nevertheless, bone loss is a minor characteristic of KS, while it is a distinctive feature of IHH. Therefore, early diagnosis and age-related replacement therapy coupled with a specific treatment for osteoporosis could be useful in preventing future severe bone loss and associated skeletal morbidity.

Gonadal dysgenesis and bone metabolism

Gonadal dysgenesis is defined as congenital hypogonadism related to abnormalities of the sex chromosomes. Because sex steroids play a central role in the acquisition and maintenance of bone mass, studies have been done to investigate bone status in patients with gonadal dysgenesis, particularly Turner's syndrome and Klinefelter's syndrome, which are the two most common types. The severe estrogen deficiency characteristic of Turner's syndrome (44, X0) is associated with a significant bone mass decrease ascribable to increased bone turnover, as shown by histological studies and assays of bone turnover markers. Estrogen therapy is followed by a significant bone mass gain and a return to normal of bone turnover markers, suggesting that it is the estrogen deficiency rather than the chromosomal abnormality that causes the bone mass deficiency, although abnormalities in the renal metabolism of vitamin D have been reported. Combined therapy with estrogens and growth hormone seems beneficial during the prepubertal period. In Klinefelter's syndrome (47XXY), serum testosterone levels are at the lower end of the normal range and dihydrotestosterone levels are low. Histological studies show depressed osteoblast function and a decrease in 5-alpha-reductase activity responsible for partial tissue resistance to androgens. Assays of bone turnover markers show evidence of increased bone turnover. The bone deficiency is most marked at the femoral neck and seems correlated with serum testosterone and estradiol levels. Androgen therapy has favorable effects on the bone only if it is started before puberty. Recent data suggest that estrogens may contribute to the development of demineralization in KS and that bisphosphonate therapy may be beneficial.

The impact of mild Leydig cell dysfunction following cytotoxic chemotherapy on bone mineral density (BMD) and body composition

BACKGROUND

Overt testosterone deficiency is associated with a reduction in BMD and alteration in body composition. However, there are few data concerning the impact of mild hypogonadism on these parameters.

PATIENTS AND METHOD

We have identified a cohort of 36 men aged < 55 years with mild Leydig cell impairment, defined by a raised LH level (LH >/= 8 IU/l) in the presence of a testosterone level in the lower half of the normal range or frankly subnormal (< 20 nmol/l), following treatment with procarbazine-containing chemotherapy regimens or high-dose chemotherapy for haematological malignancy. These men underwent measurements of BMD (measured by dual-energy X-ray absorptiometry (DXA), single energy X-ray absorptiometry (SXA) and quantitative CT (QCT)), body composition (DXA), markers of bone turnover, serum lipids and serum IGF-1. To allow for changes that may be directly attributable to the underlying disease or its treatment, results were compared with those obtained in 14 men who had received the same chemotherapy for the same diseases but had normal LH and testosterone levels (controls).

RESULTS

When data from all 50 men were considered together there were significant reductions in BMD of the lumbar spine both by DXA (Z = - 0.34, P = 0.01) and QCT (Z = - 1.5, P < 0. 0001), at the femoral neck (Z = - 0.52, P < 0.0001) and distal forearm (Z = - 0.21, P = 0.05). Mean femoral neck BMD was significantly lower in patients compared with controls (Z = - 0.68 vs. Z = - 0.11, P = 0.05) and there was a nonsignificant trend towards lower lumbar spine BMD measured by QCT (Z = - 1.64 vs. Z = - 1.10; P = 0.09). In addition, serum testosterone level and testosterone:LH ratio significantly correlated with femoral neck BMD (r = 0.28, P = 0.05 and r = 0.37, P = 0.008, respectively). There were no significant differences in lean body mass, fat mass and percentage fat between the patients and controls. There was, however, a difference in the distribution of body fat with a propensity for the patients to accrue truncal fat, and the serum testosterone level significantly inversely correlated with percentage of truncal fat (r = - 0.29, P = 0.04). There were no significant differences in lipid levels, IGF-1 levels or markers of bone turnover between the patients and controls.

CONCLUSIONS

These data suggest that mild Leydig cell impairment may have significant effects on bone mineral density and may result in subtle body composition changes, although in men who have received cytotoxic chemotherapy, other factors also contribute to the observed osteopenia. Testosterone replacement may be beneficial in some of these men and this requires further evaluation.