Breast cancer bone mets

ABSTRACT

Potential determinants of bone mass were investigated in a group of 70 young females (mean age 26.6 years), daughters of women studied in premenopause. Nutritional data, leisure physical activity level, lifestyle habits as well as familial similarities were assessed. The daughters' bone mineral density (BMD), measured by dual-energy absorptiometry, was significantly correlated with their body mass index (BMI) (r = 0.22), dietary vitamin D intake (r = 0.19) and their mothers' BMD (r = 0.44). Multiple regression analysis indicated that only the mothers' BMD remained an independent predictor of bone mass. Mother-daughter correlations were also observed for body weight (r = 0.24), height (r = 0.39), BMI (r = 0.29), dietary calcium intake (r = 0.20), and calcium (r = 0.20) or vitamin D (r = 0.25) intakes from dairy products. Hence, these observations support the evidence that mothers' BMD is the strongest predictor of bone mass of young women in their third decade.

ABREGE

Nous avons evalue les principaux determinants de la masse osseuse chez 70 jeunes femmes (Age moyen : 26,6 ans) dont les mires avaient ete etudiees avant la menopause. Notre evaluation a porte sur les apports nutritionnels, le niveau d'activite physique durant les loisirs, le mode de vie et les antecedents familiaux. Nous avons mesure la density osseuse de la colonne Tombaire (DO) par densitometrie biphotonique. Afin de determiner (influence de l'heredite et de l'environnement, ces parametres ont ate compares a ceux des metres. La DO des fines etait en relation significative avec celle de leur mere (r = 0,44), l'indice de masse corporelle (IMC) (r = 0,22) et I'apport alimentaire en vitamine D (r = 0,19). Par rEgression multiple, seule la DO des metes a ete associae i la DO des filles. Des correlations mere-fine ont etc observees pour le poids (r = 0,24), la taille (r = 0,39), l'IMC (r = 0,29), I'apport en calcium (r = 0,20) et les apports en calcium (r = 0,20) ou en vitamine D (r = 0,25) provenant des produits laitiers. Ces observations suggerent que la DO de la mere est le principal determinant de la masse osseuse chez les jeunes femmes dans la trentaine.

The risk of osteoporosis is determined later in life by the peak bone mass achieved in adulthood and the importance of subsequent bone loss. Understandably, much research has been focused on prevention of age- and menopause-related bone loss, but less attention has been given to the achievement of peak skeletal mass.

Longitudinal studies on peak bone mass reveal that while peak bone mass in the hip is reached in women in their early 20s, 12 consolidation of bone mass continues toward the end of the third decade in the lumbar spine and forearm.3-6 Therefore, the identification of factors affecting women's bone density in the third decade is an important aspect of attempts to prevent osteoporosis. Peak bone mass is influenced by the complex and ongoing interaction between genetics and environmental factors, with genetics being considered one of the major determining factors. Studies of intrapair monozygotic and dizygotic twins suggest that the estimated heritability of bone mass at different sites varies between 57% and 90%.7-12

Investigations on familial resemblance of bone mass have yielded conflicting results. Premenopausal daughters of women with osteoporosis or hip fractures present lower bone mass than premenopausal daughters without a family history of osteoporosis.13,14 Between parents and children, correlations for bone mass at different skeletal sites have been observed to vary between 0.30 and 0.70. 11-20 Three-generation studies too have illustrated familial similarities in bone mass with correlations varying between 0.30 and 0.62. 21,22 However, some authors have found no consistent evidence of significant bone mass resemblance between mothers and daughters.23 It has been shown that genetic similarities of bone mass decrease with the increasing age of family members.24 Furthermore, familial bone mass resemblance is not necessarily due entirely to the genetic transmission of traits and may be partially explained by common lifestyle habits of family members. Calcium intake, physical activity, smoking, consumption of caffeine and alcohol are a few of the numerous lifestyle factors associated with variability in bone density and rates of bone loss.25-30

Most studies in young women have not examined all potential factors that can influence bone mass. The aim of this investigation was to evaluate the main determinants of bone mass in a group of young females aged over 18, daughters of women already studied in premenopause, and to assess mother-daughter similarities in bone mass, anthropometric data as well as environmental factors such as calcium and vitamin D intakes.

METHODS

Daughters, aged 18 to 35 years, of French Canadian women who had already been studied 10 years ago while in premenopause 31 and subsequently in perimenopause 32 were invited to participate in the present study. Of 95 eligible daughters who were enrolled, 70 completed the study. The exclusion criteria were actual pregnancy or breast feeding, history of cancer, abnormal thyroid function, chronic anovulation, early menopause or oophrectomy, myalgic encephalomyelitis and drug abuse. Fifty-eight mothers with an average age of 44 years old when studied in premenopause, were involved in the comparison. The group of daughters included 16 pairs of sisters, All participants had given their written informed consent.

General data, as well as those relative to lifestyle habits, were collected by an interviewer with the use of a questionnaire. Some data referred to the actual state of the subject such as age, civil status, general state of health, smoking habits, consumption of alcohol, caffeine and use of vitamin and mineral supplements. Other data referred to lifetime history such as medical history, use of medication, age at first menarche and history of amenorrhea.

Dietary assessment was done with a 5-day food record (4 weekdays and I weekend day), mailed with proper instructions to each participant, brought to the interview and reviewed with a dietician. Food records were coded and intakes calculated with the Nutrient Analysis Program.33 The distribution of calcium and vitamin D intakes per food group and meal was also analyzed.34 Moreover, intakes of calcium and vitamin D were assessed with a food frequency questionnaire.

The level of leisure physical activity was determined using a questionnaire including the most popular social and sport activities (dancing, aerobics, golf, bowling, skating, etc.), specifying for each the frequency of practice, duration in minutes per session, intensity in METS according to a recent Compendium of physical activity.35 The daily energy expenditure (kcal/day) was then calculated by multiplying the METS by the body weight.

Height (in) was measured with the subjects in stocking feet, using a vertical wall scale, and weight (kg) was measured without shoes and heavy clothing on a hospital platform scale. Body mass index (BMI) was then calculated in kg/m^sup 2^. For mothers, the values measured 10 years before (in premenopause) were used.31

Serum ionized calcium (adjusted to pH 7.40) was measured within an hour after sampling on an ICA 1. Serum creatinine, total calcium, inorganic phosphorous, albumin and alkaline phosphatase were measured on the day of sampling by automated colorimetry on a Paramax analyzer (Dade). Serum for all other tests was kept at -20 deg C and thawed only once before batch measurement with commercially available kits. When doubtful, the state of ovarian function was determined measuring FSH and LH, as well as estradiol. Thyroid function was assessed in all participants by measuring TSH, T3 and total thyroxine. Osteocalcin (Immunotopics, Nichols Institute Diagnostics, San Juan Capistrano, CA; between assay CV: 6.7%) and 25-hydroxy Vitamin D (Incstar, Stillwater, MN; between assay CV: 10.5%) were measured in duplicate using commercial radioimmunoassays. Serum 1,25 dihydroxy Vitamin D was determined by a calf-thymus radioreceptor assay after separation by HPLC.36 The between assay CV for this measurement was 3.7%. Serum PTH was evaluated with an in-house radioimmunoassay (between assay CV = 11.6%) recognizing large carboxyl terminal fragments of PTH.37,38