In this thesis, the importance of the growth hormone (GH)/insulin-like growth factor (IGF) system and sex steroids for male bone metabolism has been investigated, and the effects of continuous low dose GH replacement in GH deficient (GHD) adults. In a population-based sample of men, positive correlations were found between bone mineral density (BMD) and IGF-I, IGF-II, IGF binding protein (IGFBP)-3 and the testosterone/sex hormone binding globulin (SHBG) ratio. Serum IGFBP-3 and testosterone levels and weight accounted for 34% to 48% of the variation in BMD at different sites. Compared to healthy age matched controls, men with idiopathic osteoporosis had lower estradiol/SHBG ratio and higher SHBG levels. There were no differences between the groups in serum levels of IGF-I, IGFBP-3, 24 hour cumulated GH secretion or peak GH secretion. In the patients, there was a positive correlation between the estradiol/SHBG ratio and BMD in femoral neck. Treatment of patients and controls with GH 0.8 mg/day for one week resulted in similar increases in serum markers for bone turnover in both groups. Several positive correlations between indices of GH secretion and markers for bone turnover were found in the patients. Men with idiopathic osteoporosis were treated with GH, continuously (0.4 mg/day) or intermittently (0.8 mg/day for two weeks every third month), for two years followed by one year of follow-up. After two years, the BMD and bone mineral content in lumbar spine and total body and serum osteocalcin levels were increased in both groups. This increase was sustained one year post treatment. Treatment of GHD adults with a low fixed dose of GH (0.17 mg/day) for three months, resulted in increases in serum IGF-I and IGFBP-3 levels and lean body mass, and a reduction in fat mass and total and low-density lipoprotein cholesterol levels. These beneficial effects were accomplished without serious side effects. These findings indicate that: i) the sex hormone and GH/IGF systems are important in male bone metabolism, ii) a combination of subtle disturbances in these two systems could contribute to the development of male idiopathic osteoporosis, iii) GH treatment could be considered as a treatment option in this condition.

Abstract Weak and osteoporotic bones in old age are an increasing cause of mortality and painful physical impairment of the elderly, especially in the western world. Bone mineral accrual during childhood and adolescence is thought to play a vital role in preventing osteoporosis. Identifying and optimizing the factors influencing peak bone mass is thus important for the prevention of osteoporosis and related fractures. A main aim of this thesis was to investigate the potential effects of various types of weight-bearing physical activity on bone accretion in young males just out of puberty. The results from our subgroups of athletes consisting of badminton, ice hockey, and soccer players suggest that weight-bearing physical activity gives rise to regional specific bone response that is determined by the degree of impact of the activity in areas subject to mechanical loading (papers I–IV). In summary, the bone is sensitive to loading after puberty in males, and important bone mass gains can be achieved by proper amount and type of exercise. Another aim of this thesis was to studythe effect of detraining on weight-bearing and non-weight-bearing bone in a cohort of adolescent males who participated in ice hockey and soccer training. Our results indicate that exercise-induced bone mineral density benefits decline, predominantly in weight-bearing bones, after retirement from an active sports career (papers II–IV). High bone density stemming from physical loading might be at least partly preserved even by reduced physical activity at nonweight-bearing sites after about three years of reduced activity (III, IV). A final aim was to follow prospectively the development of BMD during years of reduced activity in former male athletes, and evaluate whether exercise during adolescence could be associated with fewer fractures in old age. We found fewer fragility fractures in a cohort of 400 former athletes compared to in 800 age-matched controls. Thus, high bone density stemming from previous weight-bearing physical activity may reduce the risk of sustaining fragility fractures in the elderly. Key words: physical activity, peak bone mineral density, males.

With the vast array of genetically altered (knockout) mice becoming available there is a need for quantitative, repeatable, and efficient methodologies to characterize the phenotypic consequences of knocking out specific genes. Since knockout animals often have the ability to compensate for a single missing gene, it is important to examine the structural, material and morphological properties to obtain a thorough understanding of the changes occurring. For this project, femurs of knockout mice were first scanned using microcomputed tomography (micro-CT) to obtain high-resolution images of the trabecular bone in the distal femur, as well as cortical bone in the mid-diaphysis. After scanning, the femurs were tested to destruction in four-point bending at the mid-diaphysis about the medial lateral axis of the femur. These methodologies allowed quantification of (1) morphologic properties such as bone volume fraction, trabecular properties and 2nd moment of the area (2) structural properties such as stiffness, maximum load at failure, and post yield deformation and (3) material properties such as bone mineral density, elastic modulus and yield strength. As part of two independent studies, two different knockout mice, cyclooxygenase-2 (COX-2 -/-) and Apolipoprotein E (APOE -/-), were examined for structure-function relationships using these methodologies. COX-2 knockout mice were found to have decreased mineral content in their femurs, and increased post yield deformation. APOE knockout mice at 10 weeks of age had decreased bone mass and structural properties. However, by 40 weeks of age APOE deficient mice caught up to and exceeded the structural properties and bone mass of their wild type counterparts.

No description available.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

In this thesis a method was developed to reconstruct both the 3D shape and the BMD distribution of bone structures from Dual-energy X-ray Absorptiometry (DXA) images. The method incorporates a statistical model built from a large dataset of Quantitative Computed Tomography (QCT) scans together with a 3D-2D intensity based registration process. The method was evaluated for its ability to reconstruct the proximal femur from a single DXA image. The resulting parameters of the reconstructions were subsequently evaluated for their hip fracture discrimination ability. The reconstruction method was finally extended to the reconstruction of the lumbar vertebrae from anteroposterior and lateral DXA, thereby incorporating a multi-object and multi-view approach. These techniques can potentially improve the fracture risk estimation accuracy over current clinical practice. / En esta tesis se desarrolló un método para reconstruir tanto la forma 3D de estructuras óseas como la distribución de la DMO a partir de una sola imagen de DXA. El método incorpora un modelo estadístico construido a partir de una gran base de datos de QCT junto con una técnica de registro 3D-2D basada en intensidades. Se ha evaluado la capacidad del método para reconstruir la parte proximal del fémur a partir de una imagen DXA. Los parámetros resultantes de las reconstrucciones fueron evaluados posteriormente por su capacidad en discriminar una fractura de cadera. Por fin, se extendió el método a la reconstrucción de las vértebras lumbares a partir de DXA anteroposterior y lateral incorporando así un enfoque multi-objeto y multi-vista. Estos técnicas pueden potencialmente mejorar la precisión en la estimación del riesgo de fractura respecto a la estimación que ofrece la práctica clínica actual.

Metabolic bone disease is a frequent complication of Crohn’s disease (CD) with the pathogenesis of reduced bone mass in CD reported to include body weight, disease severity, disease treatments and surgery, physical activity and nutritional status. To date, there have been no studies to examine the prevalence of osteopenia and osteoporosis in an Australian CD population. Similarly, the roles of disease state and treatment, lifestyle factors and the role of body composition in the development of bone loss in CD have not been examined in an Australian CD cohort to date. This thesis has sought, for the first time, to determine the prevalence and severity of bone loss in an Australian CD population and to examine the relationship between various clinical, genetic, lifestyle and treatment variables. The role of body composition in bone loss was assessed by close examination of the muscle-bone relationship by dual-energy X-ray absorptiometry (DXA) and the local muscle-bone unit by peripheral quantitative computed tomography (pQCT) so that informed targeted treatment strategies may be implemented. Study 1 assessed the prevalence of bone loss and both molecular and clinical risk factors for bone loss in a large Crohn’s disease population. Bone mineral density (BMD) data were combined with clinical information and correlated with single nucleotide polymorphisms within the TNF-α, interleukin-10, and NOD2/CARD15 genes. Study 2 examined the independent effects of body composition and muscle strength on regional and whole body BMD in a cohort of CD patients to determine their relative importance to bone strength in this population. Study 3 used pQCT for the first time in a CD population to assess the functional muscle-bone unit in order to determine if the high prevalence of low bone mass reported in CD patients is mediated by altered body composition, in particular muscle mass and strength. Study 1 revealed 45% of CD patients had previously been diagnosed with osteopenia and 18% with osteoporosis. Both the TNF-α “GT” haplotype and the -857 “CC” genotype showed strong associations with bone mineral density overall (p=0.003 and p=0.002, respectively). Body mass index (p=0.01) and previous bowel resection in females (p=0.03) were predictive of a higher spine bone density, whilst body mass index (p=0.003) and the effect of years since first bowel resection (p=0.02) remained independent predictors of proximal femur bone mineral density. When bone mineral density was assessed in Study 2, the prevalence of osteopenia and osteoporosis was 32% and 17%, respectively, with osteopenia more common at the hip and osteoporosis more common at the spine. In multiple regression analyses, appendicular muscle mass was an independent predictor of whole body and regional BMD while lean mass was an independent predictor at the hip. Neither grip strength nor fat mass were independently associated with BMD. Of the components of body composition, muscle mass was strongly associated with regional and whole body bone mineral density. When the muscle-bone unit was assessed using pQCT in Study 3 to further examine this relationship, CD patients demonstrated lower tibial shaft mass, tibial shaft cortical cross-sectional area, and proximal tibia bone mineral density than similarly aged healthy controls. CD subjects also had significantly lower areal bone mineral density by DXA than controls at the total body (P=0.038) and hip (P=0.019). There were no significant differences between groups for any of the muscle-bone indices assessed, such as bone mineral content/muscle cross-sectional area and bone cross sectional area / muscle strength. Together, these studies have demonstrated a high prevalence of metabolic bone disease in an Australian CD population. We were able to identify a novel protective association between a TNF-α haplotype and bone mineral density and also confirmed the importance of body mass index and intestinal resection on bone loss in this population. Furthermore, these studies indicated that lean mass, and more specifically muscle mass, was a significant independent predictor of regional and whole body BMD. Consequently, maintaining or increasing muscle mass in this patient population may have a positive effect on BMD and prevent the development of osteopenia and osteoporosis. Although only modest differences were found between CD patients and controls for areal BMD by DXA and some bone parameters by pQCT, there were no differences in indices of the muscle-bone unit. These results suggest that bone strength is adequate for muscle size and strength in our sample of male CD patients with well-controlled disease, inferring that no specific intervention is required to correct expected deficiencies in this relationship. Instead, an exercise training program introduced to this patient cohort should aim to maintain or increase bone mass through weight-bearing exercises as well as encourage the maintenance or increase in muscle mass.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Natural loss of estrogen occurring in menopausal process may contribute to various health problems many of them possibly related to oxidative stress. Decrease in circulating estrogen levels and increase in follicle stimulating hormone levels (FSH) in menopausal status are related with decrease in bone mineral density. Hormone replacement therapy (HRT) is the most common treatment to attenuate menopausal disturbances and strontium (Sr) and iron (Fe) have been suggested to influence to bone metabolism. The objectives of this study was to evaluate the influence of HRT on the activity of antioxidant enzymes (SOD, CAT, and GPx) and lipid peroxidation (TBARS) in menopausal women and to determine blood strontium and iron levels and their relationship with bone mineral density and biochemical parameters in pre and postmenopausal women with or without HRT. Blood antioxidant enzyme activities were determined in premenopausal (n=18) and in postmenopausal healthy women without (n=21) or with HRT (n=19) (mean ages: 47, 59, and 57, respectively). Whole blood Sr and Fe levels were determined by spectrometric methods (inductively coupled plasma mass spectrometry - ICP-MS and inductively coupled plasma optical emission spectrometry - ICP-OES, respectively) in premenopausal (n=17) and postmenopausal women without (n=20) or with HRT (n=19) (mean ages: 47, 60 and 57 years, respectively). Bone mineral density (BMD) was evaluated at the lumbar spine (BMD L1-L4) and femoral neck (BMD femur) by dual energy X-ray absorptiometry (DEXA). TBARS, CAT, and GPx activity were not significantly different among the groups of study. However, SOD activity was significantly lower in postmenopausal women without HRT (0.68±0.04 U/mg Hb) when compared both to premenopausal women (0.91±0.04 U/mg Hb) and to postmenopausal women with HRT (0.89±0.07 U/mg Hb). SOD activity was positively correlated to the duration of HRT in the postmenopausal groups (r=0.33, p<0.05). Blood Sr and Fe levels in premenopausal (33.66±3.57 µg L-1 and 502.09±19.90 mg L-1, respectively) and postmenopausal women without (31.47±2.58 µg L-1 and 523.65±9.91 mg L-1, respectively) or with HRT (29.74±3.02 µg L-1 and 540.30±20.24 mg L-1, respectively) were not significantly different among study groups. BMD L1-L4 and BMD femur were significantly higher in premenopausal women (1.05±0.23 and 0.84±0.02 g/cm2, respectively) when compared both to postmenopausal women without (0.90±0.37 and 0.75±0.02 g/cm2, respectively) and to postmenopausal women with HRT (0.94±0.04 and 0.74±0.02 g/cm2, respectively). However, BMD had no relationship with blood metal levels, but was negatively influenced by FSH levels (β=-0.47, p<0.01 for BMD L1-L4 and β=-0.42, p<0.01 for BMD femur) and age (r=-0.48, p<0.01 for BMD L1-L4 and r=-0.38, p<0.01 for BMD femur). We concluded that HRT antagonizes the decrease of SOD activity that occurs after menopause, suggesting that HRT may play a beneficial role in the protection against oxidative stress. It was also shown that the physiologic whole blood Sr and Fe levels had no significant effect in BMD or other biochemical parameters in pre and postmenopausal women. BMD decreased with the increased in FSH levels and with aging. / A redução natural nos níveis de estrogênio, que ocorre na menopausa pode contribuir para vários problemas de saúde muitos deles também possivelmente relacionados ao estresse oxidativo. A diminuição dos níveis circulantes de estrogênio e o aumento de hormônio folículo estimulante (FSH) em mulheres na menopausa estão sendo associados à perda óssea. A terapia de reposição hormonal (TRH) é o tratamento mais comum para atenuar os distúrbios menopáusicos e, as concentrações sanguíneas de estrôncio (Sr) e ferro (Fe) têm mostrado influenciar no metabolismo ósseo. Os objetivos deste estudo foram avaliar a influência da TRH na atividade de enzimas antioxidantes (SOD, CAT e GPx) e lipoperoxidação (TBARS); e determinar os níveis de Sr e Fe e sua relação com a densidade mineral óssea (DMO) e parâmetros bioquímicos em mulheres na pré e pós menopausa com e sem TRH. As atividades das enzimas antioxidantes foram determinadas no sangue total de mulheres na pré-menopausa (n= 18) e na pós-menopausa sem (n= 21) e com TRH (n= 19); a idade média dos grupos foi de 47, 59 e 57 anos, respectivamente. As concentrações de Sr e Fe foram avaliadas por espectrofotometria (espectrometria de massas com plasma acoplado indutivamente - ICP-MS e espectrometria de emissão óptica com plasma acoplado indutivamente - ICP-OES, respectivamente), no sangue de mulheres na pré-menopausa (n= 17) e na pós-menopausa sem (n= 20) e com TRH (n= 19), com idade média de 47, 60 e 57 anos, respectivamente. A DMO foi determinada na lombar (L1-L4) e no colo do fêmur por absorciometria de duplo feixe de raios-X (DEXA). Em nosso estudo TBARS, CAT e GPx não foram significativamente diferentes entre os grupos. No entanto, a atividade da SOD foi significativamente menor em mulheres na pós-menopausa sem TRH (0,68±0,04 U/mg Hb) quando comparado com os grupos pós-menopausa com TRH (0,89±0,07 U/mg Hb) e na pré-menopausa (0,91±0,04 U/mg Hb). A atividade da SOD também apresentou correlação positiva com o tempo de TRH (r=0,33; p<0,05) nas mulheres menopausadas. As concentrações de Sr e Fe não diferiram entre as mulheres não menopausadas (33,66±3,57 µg L-1 e 502,09±19,90 mg L-1, respectivamente) e aquelas na pós-menopausa sem (31,47±2,58 µg L-1 e 523,65±9,91 mg L-1, respectivamente) ou com TRH (29,74±3,02 µg L-1 e 540,30±20,24 mg L-1, respectivamente). A DMO da L1-L4 e fêmur foi maior nas mulheres que não estavam na menopausa (1,05±0,23 e 0,84±0,02 g/cm2, respectivamente) quando comparado com os grupos de mulheres na pós-menopausa sem (0,90±0,37 e 0,75±0,02 g/cm2, respectivamente) e com TRH (0,94±0,04 e 0,74±0,02 g/cm2, respectivamente). No entanto, a DMO não apresentou correlação com as concentrações de metais encontradas. A DMO foi negativamente influenciada pelos níveis de FSH (β=-0,47, p<0,01 para DMO L1-L4 e β=-0,42, p<0,01 para DMO fêmur), e pela idade (r=-0,48, p<0,01 para DMO L1-L4 e r=-0,38, p<0,01 para DMO fêmur). Concluiu-se que a TRH antagoniza a diminuição da atividade antioxidante da SOD que ocorre após a menopausa, sugerindo o papel protetor da terapia contra o estresse oxidativo. Também demonstramos que as concentrações sanguíneas de Sr e Fe encontradas não exerceram efeito significativo na DMO e outros parâmetros bioquímicos e não foram influenciadas pela menopausa ou pela TRH em mulheres na pré e pós-menopausa. A diminuição na DMO observada foi em decorrência do aumento nos níveis circulantes de FSH e do processo de envelhecimento.

No description available.

A Osteoporose é uma doença esquelética caracterizada pelo comprometimento da resistência óssea predispondo a um risco aumentado de fraturas em mulheres na pósmenopáusa e na população idosa. O processo de remodelamento ósseo é mediado pela atividade dos osteoblastos na formação e a atividade dos osteoclastos na reabsorção da matriz óssea. Entre os vários fatores que modulam o processo de ressorção óssea estão os hormônios esteróides sexuais. Desta forma, a diminuição dos estrogênios circulantes, como ocorre na menopausa e na Falência Ovariana Prematura (FOP) resulta em uma maior perda da massa óssea. A FOP é uma condição definida como a falência da função ovariana antes dos 40 anos de idade, causando amenorréia, hipogonadismo e níveis elevados de gonadotrofinas. Vários estudos têm sugerido que esta falência gonadal possa ser uma doença genética, sendo o gene do receptor do FSH (FSHR), considerado um dos principais genes candidatos. Entretanto faltam estudos consistentes capazes de avaliar a influência destas variantes genéticas sobre a densidade mineral óssea assim como o risco de osteoporose. Assim, estudou-se uma coorte de 32 mulheres com FOP acompanhadas na Unidade de Endocrinologia Ginecológica, Serviço de Endocrinologia do Hospital de Clínicas de Porto Alegre, com os objetivos de determinar a freqüência de alterações na DMO e analisar uma possível associação entre variáveis hormonais e densidade mineral óssea comparando-as com um grupo de referência composto por 80 mulheres, sendo 25 mulheres na pré-menopausa (PRE-M) e 55 mulheres na pós-menopausa (POS-M). Também foi pesquisado se a presença de polimorfismos do gene do receptor do FSH estava associada com alterações na densidade mineral óssea no grupo FOP. Variáveis clínicas e hormonais foram obtidas, assim como a densitometria óssea foi realizada em todas as pacientes de ambos grupos, porém a análise da freqüência das variantes Ala307Thr e Ser680Asn do exon 10 do gene do FSHR foi realizada somente das pacientes do grupo FOP. A densitometria óssea de cada paciente foi classificada como massa óssea normal ou baixa massa óssea (osteopenia ou osteoporose) pelos critérios da OMS. O IMC apresentou correlação positiva com a DMO do fêmur total (p<0.05). A freqüência de baixa massa óssea foi significativamente maior no grupo FOP do que no grupo POS-M (p=0,042). Entretanto, quando a análise foi controlada pelo uso ou não de terapia hormonal, os grupos não apresentaram diferença significativa. Identificou-se maior freqüência de baixa massa óssea em L1-L4 no grupo FOP (p<0,001) enquanto o grupo de referência POS-M apresentou maior freqüência de baixa massa óssea no fêmur total (p<0,001). Não houve associação entre as variantes Ala307Thr e Ser680Asn do gene do FSH e a densidade mineral óssea (DMO em g/cm2) em coluna ou fêmur total. Concluindo, o grupo de pacientes com FOP apresentou maior frequência de alteraçoes na DMO, em especial em coluna, quando comparado com o grupo de referência na pós-menopausa. Embora os polimorfismos estudados no exon 10 do gene do FSHR possam modificar a ação do FSH, estas variantes genéticas parecem não ter influência sobre a DMO das pacientes com FOP. Entretanto, estudos longitudinais são necessários para confirmar os resultados do presente estudo. / Osteoporosis is a skeletal disease characterized by impairment of bone strength predisposing to an increased risk of fractures in postmenopausal women and in the elderly population. The process of bone remodeling is mediated by the activity of osteoblasts in the formation and activity of osteoclasts in the resorption of bone matrix. One of the factors modulating bone resorption is sex steroid hormones. Thus, the decline of circulating estrogens, as occurs in menopause and in premature ovarian failure (POF) results in greater loss of bone mass, POF is a condition defined as the failure of ovarian function before the age of 40 years, causing amenorrhea, hypogonadism and high levels of gonadotropins. Several studies have suggested that this gonadal failure can be a genetic disease, and the gene of the FSH receptor (FSHR), is considered as one of the leading candidate genes. Nonetheless, there is lacking studies that could consistently assess the influence of these genetic variants on the bone mineral density and the risk of osteoporosis. Therefore, a cohort of 32 women presenting POF and being followed at the Gynecological Endocrinology Unit, Division of Endocrinology, Hospital de Clinicas de Porto Alegre, was studied, with the objectives of determining the frequency of changes on BMD and analyze a possible association between hormonal variables and BMD, compared to a reference group composed of 80 women, with 25 in pre-menopausal (PRE-M) and 55 women in post-menopausal (POS-M). There was also searched if the presence of FSH receptor polymorphisms was associated with changes in the in bone mineral density in the group of POF. Clinical and hormonal variables were obtained as well as bone densitometry was performed in all patients in both groups; however, the analysis of the frequency of Ala307Thr and Ser680Asn variants of exon 10 of the gene of FSHR was performed only in the group of POF. Bone densitometry of each patient was classified as normal bone mass or low bone mass (osteopenia or osteoporosis) by the WHO criteria. BMI showed a positive correlation with BMD of the total femur (p <0.05). The frequency of low bone mass was significantly higher in the group of POF patients than in the POS-M group (p = 0042). However, when the analysis was controlled by the use of hormonal therapy, the no statistical difference was observed. A higher frequency of low bone mass in L1-L4 was identified in the POF group (p <0001) while the reference group of POS-M showed higher frequency of low bone mass in the total femur (p <0001). There was no association between the Ala307Thr and Ser680Asn variants of the FSHR gene and bone mineral density (BMD in g/cm2) in L1-L4 or in femur total. In conclusion, POF group presented a higher frequency of changes on BMD, mainly in lumbar spine, when compared to the reference POS-M group. While the studied polymorphisms in the exon 10 of the FSHR gene may modify the FSH actions, these genetic variants appear to have no influence on BMD of these patients. However, longitudinal studies are needed to confirm the results of this study.