Longitudinal study of calcium metabolism in male puberty. I. Bone mineral content, and serum levels of alkaline phosphatase, phosphate and calcium

Age-dependent sex differences in calcium and phosphate homeostasis

BACKGROUND

Sex differences in calcium and phosphate have been observed. We aimed to assess a relation with age.

METHODS

We used the laboratory values of serum calcium, phosphate and albumin from three different samples ( 2005, 2010 and 2014 years) using the hospital information system of Erasmus MC, Rotterdam. The samples were divided into three age groups: 1-17, 18-44 and ≥45 years. Sex differences in calcium and phosphate were analyzed using ANCOVA, adjusting for age and serum albumin. Furthermore, sex by age interactions were determined and we analyzed differences between age groups stratified by sex.

RESULTS

In all three samples there was a significant sex × age interaction for serum calcium and phosphate, whose levels were significantly higher in women compared to men above 45 years. No sex differences in the younger age groups were found. In men, serum calcium and phosphate levels were highest in the youngest age group compared to age groups of 18-44 and ≥45 years. In women, serum calcium levels were significantly higher in the age group 1-17 and the age group ≥45 years compared to the 18-44 years age group. In women, serum phosphate was different between the three different age groups with highest level in the group 1-17 years and lowest in the group 18-44 years.

CONCLUSION

There are age- dependent sex differences in serum calcium and phosphate. Furthermore, we found differences in serum calcium and phosphate between different age groups. Underlying mechanisms for these age- and sex- differences are not yet fully elucidated.

Osteoporosis in men

Osteoporotic fractures are the leading cause of morbidity and mortality among aging men. 30% of all hip fractures occur in men, and mortality resulting from not only the hip fracture, but also the spine and other major osteoporotic fractures, is significantly higher in men than in women. As in women, hypogonadism is the best documented risk factor for developing osteoporosis in men. In older men, testosterone levels are negatively correlated with the risk of fractures, and it seems that this age-related testosterone deficiency should not be considered as one of the many causes of secondary osteoporosis, rather one of the major and most important mechanisms of senile osteoporosis. Acute hypogonadism induced by ablation treatment for prostate cancer (surgical or pharmacological castration, antiandrogen therapy) is associated with an extremely high risk of fracture. Other documented causes of bone loss in men are cigarette smoking and alcohol abuse, and a number of diseases that require corticosteroid treatment. Pharmacotherapy of osteoporosis should be recommended to all men with a diagnosed osteoporotic fracture and all men with a high 10-year absolute fracture risk (FRAX^TM). Not all drugs registered for the treatment of postmenopausal osteoporosis have been registered for the treatment of osteoporosis in men, and others have not been the subject of long-term and costly clinical trials required for such registration. The risk reduction of new fractures was documented only for treatment with zoledronic acid. Risedronate, strontium ranelate, teriparatide, and denosumab in men increase in bone mineral density comparable to that seen in postmenopausal women.

Serum calcium and phosphorus concentration and alkaline phosphatase activity in healthy children during growth and development

Introduction. Many changes happen during growth and development in an organism as a result of important hormone changes, especially biohumoral ones. These changes make a problem when interpreting biochemical results in pediatric population. The most important changes are intensive calcium and phosphorus metabolic turnover in bone tissue with changes in alkaline phosphatase activity as a result of osteoblast activity. The aim of this study was to follow the serum calcium and phosphorus concentration and alkaline phosphatase activity in children 1-15 years old in different growth and development period and of different sexes and to fortify the influence of growth and development dynamics on biohumoral status in healthy male and female children. Material and methods. We evaluated 117 healthy children of both sexes from 1-15 years of age and divided them into three age groups: 1-5, 6-10 and 11-15 years. We followed the serum calcium and phosphorus concentration and alkaline phosphatase activity in different groups and in different sexes. Results and conclusion. Our investigation found significantly higher values of serum calcium in boys than in girls with no important changes between the age groups and significantly higher values of serum phosphorus in the youngest age group in all children and in different sexes with no important sex differences. Alkaline phosphatase activity followed the growth spurt and was the biggest in 6-10 years group in girls and in 11-15 years group in boys.

Low-dose estrogen treatment suppresses periosteal bone formation in response to mechanical loading

Estrogen and exercise influence cortical bone formation. Both affect bone during growth, but with complex interactions. We hypothesized that estrogen reduces the osteogenic response caused by exercise at the periosteal surface of bone, while it enhances bone formation on the endocortical surface. To test our hypothesis, 16 young (8 weeks old) male Sprague-Dawley rats were randomized into two groups: (1) low-dose 17-alpha ethynylestradiol treatment+bone loading (EE2) or (2) vehicle-treated+bone loading (vehicle). We applied controlled loading to the right ulna at a peak force of 17 N, 2 min/day, 3 days/week for 5 weeks to simulate exercise. The left nonloaded ulna served as an internal control for loading. Mechanical loading increased cortical area (7.7%) and bone mineral content (8%) in the vehicle-treated group (P < 0.05) but only slightly increased cortical area in the EE2 group (P = 0.08). Histomorphometry showed 1 week of mechanical loading increased periosteal bone formation rate by 29% in the vehicle group and this response was reduced (P < 0.05) to only 15% in the EE2 group. At the endocortical surface, there were no differences in the loading response between the vehicle and EE2-treated groups. We conclude low-dose EE2 suppresses the mechanical loading response on the periosteal surface of long bones, but had no effect on the loading response at the endocortical bone surface in growing male rats.

Commercial diet induced hypothyroidism due to high iodine. A histological and radiological analysis

A number of puppies of the School Hospital of the Faculty of Veterinary Science-UBA showed bone changes. Measurement of the iodine content of the commercial diet showed a significant increase in its content. Iodine excess causes alterations in thyroid function and morphology, and its hormones have a direct action on bone formation. Three groups of puppies were fed on different diets: a home-prepared diet, a commercial diet (containing 5.6 mg potassium iodide/kg dry food), and a home-prepared diet supplemented with 5.6 mg potassium iodide/kg dry food. Groups B and C developed hypothyroidism. A significant decrease (p<0.05) in the styloid apophyseal surface was found in groups B and C vs. A, determined by radiography. Histologically, the hypertrophied cartilage was shorter in groups B and C than in group A (p<0.0001). The present results suggest that commercial diets with a high iodine content may cause hypothyroidism and changes in bone metabolism.

Abnormalities in skeletal growth in children with juvenile rheumatoid arthritis

A review of the acquisition of peak skeletal mass in normal children and studies that have been reported for children with JRA lead to the following tentative conclusions: (1) The appendicular skeleton is predominantly the overall status of skeletal mineralization; (2) a failure to develop adequate bone mineralization is virtually universal in children with JRA and is characterized by a failure of bone formation. A failure to undergo the normal increase in bone mass during puberty is common in children with JRA and markedly decreases their potential to achieve an adequate peak skeletal mass; (3) the onset of accelerated skeletal maturation with puberty is a critical period of potential intervention in JRA. Conversely, therapeutic interventions later during adolescence offer less promise of reversal of inadequate bone mineralization; and (4) the most important therapeutic maneuver is likely to be control of the inflammation process, although there is hope, at present unsubstantiated, that supplemental dietary calcium and vitamin D, and normalization of physical activity, many lead to some "catch-up" mineralization.

[Peak bone mass: facts and uncertainties]

Peak bone mass, which can be defined as the amount of bony tissue present at the end of the skeletal maturation, is an important determinant of osteoporotic fracture risk in adulthood. The techniques of single or dual energy absorptiometry measure the so-called "areal" or "surface" bone mineral density (BMD), a variable which has been shown to be directly related to bone strength. During puberty the gender difference in bone mass becomes expressed. This difference appears to be essentially due to a more prolonged bone maturation period in males than in females, with a larger increase in bone size and cortical thickness, as there is no significant sex difference in the volumetric trabecular density at the end of pubertal maturation. At the beginning of the 3rd decade, there is a large variability in the normal values of areal BMD in axial and appendicular skeleton. This large variance, which is observed at sites particularly susceptible to osteoporotic fractures in adulthood, such as lumbar spine and femoral neck, is barely reduced after correction for statural height, and does not appear to substantially increase during adult life. It is generally accepted that peak bone mass at any skeletal site is attained in both sexes during the mid-thirties. However, recent studies indicate that in healthy caucasian females, bone mass accumulation can virtually be completed before the end of the second decade, for both lumbar spine and femoral neck. Several variables are supposed to influence bone mass accumulation during growth: heredity, sex, diet components, endocrine factors, mechanical forces, and exposure to risk factors.(ABSTRACT TRUNCATED AT 250 WORDS)

The contribution of hypogonadism to the development of osteoporosis in thalassaemia major: new therapeutic approaches

OBJECTIVE

The osteoporosis seen in thalassaemia major is of multifactorial origin. The aim of the study was to evaluate the contribution of hypogonadism to the development of this osteoporosis and to assess the efficacy of new sex hormone replacement therapy regimens.

DESIGN AND PATIENTS

Sixty-seven patients were studied: 12 were hypogonadal, 32 had been on previous hormone replacement therapy (conjugated oestrogens plus medroxyprogesterone for females, depot testosterone esters for males); 10 had received continuous courses of treatment and 22 3-monthly on/off courses, and 22 were eugonadal without previous replacement therapy. Twenty-seven of the above patients were evaluated prospectively at 16 and 32 months during different therapeutic approaches (12 without treatment, 7 on continuous replacement and 8 on/off schemes followed by continuous therapy during the second observation period). The continuous schemes comprised either transdermal oestradiol (100 micrograms) plus medroxyprogesterone for females or hCG to produce serum testosterone concentrations within normal range, for males.

MEASUREMENTS

Bone mineral density (BMD) and bone mineral content (BMC) of lumbar spine and distal end of radius were measured by dual-energy X-ray absorptiometry.

RESULTS

Spinal BMD was found to be more than 30% lower than that of controls matched for sex and age with no difference between sexes. Radial BMD was less impaired and showed significantly (P < 0.01) higher levels in males (decrease of 5.8% +/- 2.3, mean +/- SD) than in females (-14.5 +/- 3.4%, mean +/- SD). In the retrospective evaluation it was found that the hypogonadal group had the lowest (P < 0.0001) BMD levels (0.62 +/- 0.01, mean +/- SE) and the highest were observed on the continuous replacement group (0.83 +/- 0.04), whereas the values of the other groups were similar. In a multiple regression analysis model it was found that only sex steroid levels were related to the BMD measurements (for oestradiol t = 2.6, P = 0.01 and for testosterone t = 6.5, P = 0.0001), whereas parameters related to haemolytic anaemia and desferrioxamine treatment were not. In the prospective study the continuous replacement group increased BMD and BMC values more than the on/off treatment courses (P = 0.01).

CONCLUSIONS

Hypogonadism seems to play an important role in the development of osteopenia-osteoporosis in thalassaemia major; continuous hormone replacement therapy with transdermal oestrogen for females or hCG for responding males best improves the bone density parameters.

The two faces of growth: benefits and risks to bone integrity

Bones grow by two processes: cortical bone is made by periosteal apposition (growth in width), and cancellous bone is made by endochondral ossification (growth in length). In both the axial and appendicular skeleton, about half of peak adult bone mass is accumulated during the adolescent growth spurt, which occurs two years earlier in girls than in boys, and is under pituitary control via interactions between growth hormone and sex hormones. Throughout growth, but particularly during adolescence, the ability of bone to adapt to mechanical loading is much greater than after maturity. This is the main reason why the effects of physical activity on bone are greater in cross-sectional studies in young athletes than in longitudinal studies in previously sedentary adults. In wild animals, by the time growth has ceased, the bones must be as strong as they will ever need to be, and attainment of further strength after cessation of growth would serve no biologic purpose. Adaptation of growing bone to mechanical loading is the purpose of the mechanostat, which enables physiologic adaptation in individuals to establish and maintain a species-specific property of the bones that is determined by evolutionary adaptation in populations. But growth confers risks as well as benefits to the skeleton. The large increase in incidence of upper extremity (particularly lower forearm) fractures, coincident with the adolescent growth spurt in both sexes, is due to an increase in cortical porosity as a consequence of an increase in intracortical bone turnover, which supplies some of the calcium needed by the growing ends of the long bones. This enables an increased demand for calcium to be spread over a longer time, analogous to the cyclic physiologic osteoporosis which occurs during the antler growth cycle in deer. The subsequent decline in cortical porosity is responsible for the continued increase in radial bone density after cessation of growth, referred to as consolidation. In the present state of knowledge, an increased incidence of fracture during the adolescent growth spurt is the inescapable consequence of an appropriate level of physical activity, and is the price that has to be paid in order to maximize bone accumulation during growth and minimize fracture risk in old age.

Peak bone mass

Peak bone mass, which can be defined as the amount of bony tissue present at the end of the skeletal maturation, is an important determinant of osteoporotic fracture risk. Measurement of bone mass development. The bone mass of a given part of the skeleton is directly dependent upon both its volume or size and the density of the mineralized tissue contained within the periosteal envelope. The techniques of single-1 and dural-energy photon or X-ray absorptiometry measure the so-called 'areal' or 'surface' bone mineral density (BMD), a variable which has been shown to be directly related to bone strength. Bone mass gain during puberty. During puberty the gender difference in bone mass becomes expressed. This difference appears to be essentially due to a more prolonged bone maturation period in males than in females, with a larger increase in bone size and cortical thickness. Puberty affects bone size much more than the volumetric mineral density. There is no significant sex difference in the volumetric trabecular density at the end of pubertal maturation. During puberty, the accumulation rate in areal BMD at both the lumbar spine and femoral neck levels increases to four- to sixfold over a 3- and 4-year period in females and males, respectively. Change in bone mass accumulation rate is less marked in long bone diaphyses. There is an asynchrony between the gain in statural height and bone mass growth. This phenomenon may be responsible for the occurrence of a transient period of a relative increase in bone fragility that may account for the pattern of fracture incidence during adolescence.(ABSTRACT TRUNCATED AT 250 WORDS)

Bone mineral density during puberty in western Canadian children

To assess the influence of puberty and its associated changes in body weight and height on bone mineral density (BMD), lumbar spine (L2-L4) and femoral neck BMD were measured in 74 healthy, active children (9-16 years) using dual-photon absorptiometry. Competitive swimmers were recruited to minimize the potential effect variability in mechanical loading regime may have on bone density of the lumbar spine. Tanner staging was used to assess stage of puberty. Current dietary calcium intake was assessed by analysis of 6-day dietary records. Significant differences in spinal and femoral neck BMD occurred between early (Tanner 1 and 2) and late stages of puberty (Tanner 4 and 5), P < 0.05. A significant correlation was found between bone density and dietary calcium intake. However stepwise regression analyses demonstrated stage of puberty or body weight were the only factors which significantly affected spinal BMD, accounting for 77% and 68% of the variability respectively; while at the femoral neck, body weight accounted for 52% of the variability. These results demonstrate that when potential interacting factors are controlled for through regression analyses, differences in BMD occur mainly as a function of puberty and the associated gains in body weight.

Osteopenia in men with a history of delayed puberty

BACKGROUND AND METHODS

The effect of delayed puberty on peak bone mineral density in men is unknown. To determine whether such a delay reduces normal peak bone density and leads to osteopenia during adulthood, we measured radial bone mineral density by single-photon absorptiometry and spinal bone mineral density by dual-energy x-ray absorptiometry in 23 men who had a history of constitutionally delayed puberty and 21 men who underwent normal puberty. Their mean ages were 26 and 24 years, respectively. The groups were matched for other factors known to affect bone mass.

RESULTS

The mean (+/- SD) radial bone mineral density was significantly lower in the men with a history of delayed puberty than in the normal men (0.73 +/- 0.07 vs. 0.80 +/- 0.05 g per square centimeter; P less than 0.0002). Spinal bone mineral density was also significantly lower in the men with delayed puberty than in the normal men (1.03 +/- 0.10 vs. 1.13 +/- 0.11 g per square centimeter; P less than 0.003). Radial bone density was at least 1 SD below the mean value for the normal men in 15 of the 23 men with a history of delayed puberty, and spinal bone density was similarly decreased in 10 of the 23.

CONCLUSIONS

Adult men with a history of constitutionally delayed puberty have decreased radial and spinal bone mineral density. These findings suggest that the timing of puberty is an important determinant of peak bone density in men. Because the peak bone mineral density achieved during young adulthood is a major determinant of bone density in later life, men in whom puberty was delayed may be at increased risk for osteoporotic fractures when they are older.

Urinary calcium excretion in healthy adolescents

To establish normative data for urinary calcium excretion in healthy adolescents, we measured calcium-creatinine ratios (UCa/Cr) in urine samples collected from 222 middle school teenagers of diverse racial and socioeconomic backgrounds. Median UCa/Cr were: white girls, 0.23 mmol/L per mmol/L (0.08 as mg/dl per mg/dl); black girls, 0.14 (0.05); white boys, 0.14 (0.05); and black boys, 0.08 (0.03). The 95th percentile values for UCa/Cr were: white girls, 0.54 (0.19); black girls, 0.59 (0.21); white boys, 0.68 (0.24); and black boys, 0.50 (0.18). By nonparametric analysis, girls had significantly higher UCa/Cr than boys (p less than 0.01), and whites had significantly higher urinary UCa/Cr than blacks (p less than 0.01). No significant correlation was found between Tanner stage and UCa/Cr in either sex. This study provides data for detecting adolescents with high urine calcium excretion, which should be useful clinically and in studies designed to evaluate the significance of persistent hypercalciuria.

Effect of sex steroids on peak bone density of growing rabbits

To determine the effect of sex hormones on bone density (BD) during growth, longitudinal quantitative computed tomography (QCT) measurements were obtained in growing, castrated New Zealand White rabbits following administration of normal saline, testosterone, or estrogen from 6 wk of age until the time of skeletal maturity. Vertebral QCT densities increased during growth, were highest at the time of epiphyseal closure, and were significantly greater (P less than 0.001) in hormone-treated animals. In vivo QCT measurements in 12 vertebraes correlated strongly (r = 0.92) with percentage of calcium per weight assessed in vitro by neutron activation analysis.

Testosterone regulates the haemoglobin concentration in male puberty

In a longitudinal study of male puberty 20 boys were examined every three months for at least two years. Haemoglobin concentration was determined and related to changes in serum testosterone concentrations. The data show a steep increase in serum testosterone during puberty (p less than 0.001) followed with a five months delay, by a significant increase in haemoglobin concentration (p less than 0.001). It is concluded that the steep increase in serum testosterone during puberty produces an acute stimulation of erythropoietin leading to an increase in erythrocyte production and thereby to a detectable increase in haemoglobin concentration a few months thereafter. The present study supports the idea that the selection of the relevant reference range for haemoglobin in boys should depend on the state of physical developments as expressed by serum testosterone.

Serum vitamin D metabolites are not related to growth rate, bone mineral content, or serum alkaline phosphatase in male puberty

Twenty boys were followed during their puberty for about 2 years with examinations every third month. At each examination we determined serum concentrations of 25OHD3, 1,25(OH)2D3, 24,25(OH)2D3, 25.26(OH)2D3, alkaline phosphatase (AP) and testosterone together with bone mineral content (BMC) at the distal forearm. Highly significant increases in both BMC (P less than 0.001), serum AP (P less than 0.001), and peak height velocity (PHV) followed the increase in serum testosterone. The boys were grouped according to time of maximal increase in BMC, AP, and PHV. The serum levels of the vitamin D metabolites were related to these points. No significant changes in any of the serum vitamin D metabolites were found. Thus vitamin D metabolism does not seem to be significantly influenced during the period of life when both the linear growth and bone mineralization is maximal.

Bone turnover in male puberty: a longitudinal study

In a longitudinal study of male puberty, 18 boys were examined every 3 months for at least 2 years. Serum bone Gla protein (BGP), a biochemical marker of bone formation, was determined and related to changes in serum testosterone (T), serum alkaline phosphatase (AP), serum calcitonin, and bone mineral content (BMC). The data demonstrate a steep increase in serum T during puberty (P less than 0.001), with an almost concomitant increase in serum BGP (P less than 0.001) and serum AP (P less than 0.001). Ten months after the maximal increase in serum T, the increase in BMC reached its maximum, whereas there was no significant change in the serum calcitonin. The data demonstrate that the steep increase in serum T during puberty, directly or indirectly, produces acute stimulation of bone formation (estimated from BGP and AP) followed by a highly significant increase in the integrated measurement of bone apposition (BMC).

Relationship between local and total bone mineral in normal pubertal boys

The bone mineral content of the distal forearm (BMC) using single-photon absorptiometry and total body bone mineral (TBBM) using dual-photon absorptiometry were determined in 19 normal boys at different pubertal stages. A highly significant correlation between BMC and TBBM was seen (r = 0.78, P less than 0.001) with a standard error of estimate (SEE) of 13%. Subgroups of early and late pubertal stages did not show any significant differences in the regression lines indicating an identical relationship between BMC and TBBM at various stages of pubertal development although great changes in bone mineral content take place. Due to high accuracy and reproducibility of both methods, which are non-invasive and harmless, measurement of BMC is suitable to estimate changes in total mineral content of the body. This may be of importance in various diseases with disturbance in growth and bone metabolism.

Longitudinal study of calcium metabolism in male puberty. II. Relationship between mineralization and serum testosterone

Height velocity, bone mineral content (BMC), serum concentrations of alkaline phosphatase (AP), testosterone, dehydroepiandrosterone (DHEA) and androstenedione (A-dione) were determined as a part of a longitudinal study of calcium metabolism in normal male puberty. The time of maximal increase (Tm) in concentrations was calculated for 20 boys from a curve-fitting analysis program. Highly significant correlations were found between Tm testosterone and Tm BMC (r = 0.73, p less than 0.001); Tm AP and Tm BMC (r = 0.68, p less than 0.001). The mean difference in time between Tm testosterone and Tm BMC was 4.7 months and between Tm AP and Tm testosterone 0.7 month. Our data indicate a very close relationship between testosterone, osteoblastic activity, and mineralization in normal male puberty, whereas the adrenal androgens do not seem to have a major influence on the mineralization at the male puberty growth spurt phase.