2010_olmos_bone turnover markers and bone mineral density in hypertensive

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Maturitas 65 (2010) 396402

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Maturitas

j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / m a t u r i t a s

Bone turnover markers and bone mineral density in hypertensivepostmenopausal women on treatment

Jos M. Olmos a,, Jos L. Hernndez a, Josefina Martnez a, Jess Castillo b, Carmen Valero a,Isabel Prez Pajares b, Daniel Nan a, Jess Gonzlez-Macas a

a Department of Internal Medicine, Hospital Universitario Marqus de Valdecilla, University of Cantabria, RETICEF, Santander, Spainb Centro de Salud Jos Barros, Camargo, University of Cantabria, Santander, Spain

a r t i c l e i n f o

Article history:

Received 30 August 2009

Received in revised form 7 January 2010

Accepted 8 January 2010

Keywords:

Hypertension

Thiazides

Bone mineral density

Quantitative ultrasound

Parathyroid hormone

Bone turnover markers

a b s t r a c t

Objective: To evaluate bonemineral density (BMD)and bonemetabolismin hypertensive postmenopausal

women, and to differentiate the effect of thiazides from that of other antihypertensive agents.

Subjects and methods: A community-based population of 636 postmenopausal women, 293 with hyper-

tension (160 receiving thiazides, and 133 receiving other antihypertensive treatments), and 343 control

women, were evaluated.Serum levels of aminoterminalpropeptide of type I collagen (P1NP), C-terminal

telopeptide of type I collagen (-CTX), 25-hydroxivitamin D, and intact parathyroid hormone were mea-sured by electrochemiluminiscence. BMD was determined by DXA, and heel quantitative ultrasound

measurements (QUS) with a gel-coupled device.

Results: BMD expressed as Z-score was higher in both groups of hypertensive women at all locations.

Expressed as g/cm2, it was also higher in patients on thiazides at femoral neck and lumbar spine. Only

in the latter site, differences remained significant after adjusting for potential confounding variables,

including BMI. Bone turnover markers were lower in both groups of hypertensive women, although

the difference was greater in those on thiazides. After adjusting for potential confounders, differences

remained significant only in the thiazide group.

Conclusions: Our results add evidence to the idea that thiazides are beneficial to prevent bone loss.

2010 Elsevier Ireland Ltd. All rights reserved.

1. Introduction

Osteoporosis is a disease characterized by an increase in bone

fragility, resulting in fractures induced by low-energy trauma or

even of a spontaneous nature. It is estimated that more than one-

third of all Caucasian women over the age of 50 will suffer a

fracture of the spine, hip or wrist in their life-time [1,2]. Dual X-

ray absorptiometry (DXA) is recognized as the reference method

for measuring bone mineral density (BMD), and for each standard

deviation decrease in BMD, fracture risk approximately doubles

[2]. In recent years, quantitative ultrasound (QUS) measurements

Abbreviations: BMD, bone mineral density; BMI, body mass index; BMT, bone

turnover markers; BUA, broadband ultrasound attenuation; -CTX, C-terminal

telopeptide of type I collagen; cCa, albumin-corrected serum total calcium; CV,

coefficients of variation; DXA, dual X-ray absorptiometry; eBMD, estimated bone

mineral density; FN, femoral neck; iPTH, intact parathyroid hormone; LS, lumbar

spine; NHANES III, Third National Health and Nutrition Examination Survey; P1NP,

aminoterminal propeptide of type I collagen; QUI, quantitative ultrasound index;

QUS, quantitative ultrasound measurements; SD, standard deviation; SOS, speed of

sound; TCa, serum total calcium; TH, total hip; 25OHD, 25-hydroxivitamin D. Corresponding author. Tel.: +34 942202513; fax: +34 942201695.

E-mail address: [email protected] (J.M. Olmos).

have been proposed as an alternative method for the non-invasive

assessment of skeletal status, as they reflect not only the BMD but

also qualitative aspects of bone such as elasticity, structure and

geometry [3].

On the other hand, hypertension is a chronic disease charac-

terized by progressive damage to target organs, such as the heart,

kidney and brain. Its prevalence increases with age, as osteoporo-

sis does [4]. However, the relationship between both disorders has

not been clearly established. Thus, in several studies, hyperten-

sion has been shown to be inversely correlated with bone mineral

content [5], whereas a direct relation [6] or no significant associ-

ation [7] with BMD has also been described in others. Moreover,information about the long-term effects of antihypertensive treat-

ment on BMD is scarce, except in the case of thiazides. It has been

suggested that thiazide diuretics, which are commonly used to

treat hypertension, may be of benefit in the prevention of osteo-

porosis. As a matter of fact, large epidemiologic studies, either

prospective or case-control designs, have consistently shown that

thiazides are associated with a risk reduction in osteoporotic frac-

tures [812]. In addition, in most, but not all, studies, the use

of thiazides has been associated with higher BMD in both sexes

[1317]. Moreover, a decrease in bone turnover markers has also

beenreported[13,14,1618]. However, no significant changeshave

0378-5122/$ see front matter 2010 Elsevier Ireland Ltd. All rights reserved.

doi:10.1016/j.maturitas.2010.01.007
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J.M. Olmos et al. / Maturitas 65 (2010) 396402 397

been described in QUS parameters in postmenopausal women

treated with thiazides [19].

A number of mechanisms have been proposed to explain the

positive effects of thiazides on osteoporosis. These diuretics reduce

renal calcium excretion and may cause a positive calcium balance,

decreasing plasma levels of parathyroid hormone (PTH) and thus,

reducing bone turnover [13,14,16,20]. Nevertheless, experimental

data do not fully support this hypothesis, since conflicting results

have been reported on the effect of thiazides on calciotropic hor-

mones. Both 1,25(OH)2D and PTH levels have been reported as

being decreased, unchanged, and evenincreasedin response to thi-

azide treatment [17,18,2126], suggesting that these agents might

have a direct action on bone [17,26].

The aim of the present study was to evaluate bone turnover

markers and BMD, estimated by DXA and QUS, in a population-

basedstudy of hypertensivepostmenopausal women on treatment,

andto determine the effectof thiazides andotherantihypertensive

drugs on calcium homeostasis and bone mass.

2. Subjects and methods

2.1. Study design and participants

The study population was set up with postmenopausal women

included in the Camargo Cohort Study. The Camargo Cohort is a

community-based study established to evaluate the prevalence of

metabolic bone diseases as well as the prevalence of risk factors

for osteoporosis and fragility fractures in postmenopausal women

and men older than 50 in our region. Blood analysis, including

parameters related to bone metabolism (PTH, 25OHD, and bone

turnovermarkers), DXAand QUS measurements, as wellas thoracic

and lumbar spine radiographs, were performed in each participant.

A questionnaire including diseases, treatments and risk factors

related to bone and mineral metabolism (see below) was filled out

foreveryone of them. Additionally, advantage wastakenof the fact

that the cohort was also being set up to analyze aspects related to

vascular diseases, and information on this subject (e.g., history ofdyslipidemia or hypertension, or treatment for bothdisorders) was

also collected. Participants were recruited at a Primary Care Centre

in Northern Spain, while attending for medical reasons or for their

regular health examination, whichever happened first. Because of

this routine check up, all postmenopausal women are expected to

attend the centre annually.

In the current study we have included the first 794 consecu-

tive postmenopausal women attending the clinic. Because of the

goal of the study, women whose baseline assessment revealed

the presence of diseases or treatments (other than antihyperten-

sive drugs) known to affect bone metabolism, such as primary

hyperparathyroidism, hyperthyroidism, osteoporosis, serum crea-

tinine> 151mol/l, or treatment withbisphosphonates, oestrogen,

raloxifene, strontium ranelate, teriparatide, l-thyroxinor glucocor-ticoids, were excluded. All participants were white, as more than

95%of people in our region(Cantabria). Thestudywas approved by

the local Ethics Committee, and all subjects gave written informed

consent.

At the baseline visit, women were interviewed by investiga-

tors and all participants provided data regarding the risk factors

for osteoporosis and fractures using a structured questionnaire

which included age, race, weight, height, body mass index (BMI),

age of menarcheand menopause, personal antecedents of fractures

in adulthood (>40 years), history of osteoporotic fractures among

first-degree relatives, tobacco use, dairy calcium intake, alcohol

consumption, physical exercise, number of falls in the previous

year, presence of chronic diseases (hypertension, dyslipidemia,

diabetes mellitus, urolithiasis, hyperthyroidism, hyperparathy-

roidism, etc.); and present or past use of medications, including

diuretics and antihypertensive agents. BMI was defined as weight

(kg)dividedby squared height (m2). Tobaccosmokingwas assessed

as current smoker, former smoker or never smoker. Dairy calcium

consumption was assessed by a food frequency questionnaire [3].

Regarding alcohol consumption, participants were asked for how

much they had consumed during the past 30 days and how many

times they had consumed three or more drinks per day during this

period. Habitual physical activity was classified as high (moving,

walking and working energetically and participating in vigorous

exercise), moderate (walks reasonable distances, does light house-

work shopping or equivalent, normal activities of day-to-day living

but no appreciable exercise), and sedentary (little walking outside

home, or sits in a chair or lies in bed most of the time). Hyperten-

sion was defined according to the Joint National Committee (JNC

VII) criteria. The presence of subclinical thyroid dysfunction was

excluded by determination of serum T4 and TSH levels.

2.2. Biochemical tests

Blood samples were obtained in a fasting state between 09:00

and 10:30h. Serum was divided into 0.5-ml aliquots and stored at

40 C. Serum total calcium (TCa), phosphate, glucose, creatinine,

total cholesterol, HDL-cholesterol, LDL-cholesterol, triglycerides,albumin, and total alkaline phosphatase measurements were

determined by standard automated methods in a Technicon Dax

autoanalyser (Technicon Instruments, CO, USA). TCa measure-

ments were corrected for albumin concentration (cCa) following

a previously published formula [27]. Serum concentrations of

aminoterminal propeptide of type I collagen (P1NP), C-terminal

telopeptide of type I collagen (-CTX), 25-hydroxyvitamin D3(25OHD), and intact parathyroid hormone (iPTH) were determined

by a fully automated electrochemiluminiscence system (Elecsys

2010, Roche Diagnostics, GmbH, Mannheim, Germany). The P1NP

limit of detection was 5 ng/ml (reference range between 20 and

76 ng/ml), with an intraassay and interassay coefficients of vari-

ation (CV) of 3.1% and 3.5%, respectively [28]. Intraassay and

interassay CV for-CTX were 4.2% and 4.7%, andits reference rangeof 0.1081.033ng/ml, respectively [29]. The detection limit of

serum25 OHDwas4 ng/ml, itsintraassayCV was5%,andits interas-

say CV was 8.5%. Regarding iPTH, the detection limit was 6 pg/ml,

with a normal range of 1565 pg/ml. Intraassay and interassay CV

were 5.4% and 5.9%, respectively.

2.3. DXA measurements

BMD was measured by DXA (Hologic QDR 4500, Bedford, MA,

USA) at the lumbar spine (L2L4), and proximal right femur

(femoral neck [FN], and total hip [TH]). BMD (g/cm2) for each sub-

ject was calculated by dividing the amount of bone mineral content

by the projected area of the region of interest. In vivo precision

was 0.41.5% at the different measurement sites. Results were alsoexpressed as T-score (defined as the number of standard devia-

tions [SDs] below the mean value of young women) and as Z-score

(defined as the number of SDs below the mean for women of the

same age). Only one measurement was obtained from each par-

ticipant. Quality control was performed according to the usual

standards [30].

2.4. Quantitative ultrasound measurements

Calcaneal QUS measurements were performed using the Sahara

ClinicalSonometer (Hologic,Walthman,MA, USA), which measures

bothbroadband ultrasoundattenuation (BUA) (dB/MHz) and speed

of sound (SOS) (m/s) at a fixed region of interest in the right mid-

calcaneus. The BUA and SOS results are combined to provide the


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398 J.M. Olmos et al. / Maturitas 65 (2010) 396402

Table 1

Baseline characteristics of the study population (mean SD).

On thiazides On other anti-hypertensives Control group

Age (years) 679*** 659*** 608

Weight (kg) 7314*** 7212*** 6711

Height (cm) 1556 1556 1566

BMI (kg/m2) 30.25.2*** 30.34.9*** 27.74.5

Waists circumference (cm) 10012*** 10313*** 9212

Age of menarche (years) 132 132 132

Age of menopause (years) 49

5 49

4 49

5History of falls (last year) (%) 32* 26 22

Any fracture >40 years (%) 20 18 15

Family history of fractures (%) 12 18 16

Physical activity

Sedentary (%) 6 3 3

Moderate (%) 41 48 42

High (%) 53 49 55

Current smoking (%) 11* 8* 17

Current alcohol consumption [> 2 units/day] (%) 8 10 9

Dairy calcium consumption (mg/day) 684400 663327 665314

Calcium supplements (%) 10 11 11

Vitamin D supplements (%) 8 12 9

Dyslipidemia (%) 36** 44*** 24

Diabetes mellitus (%) 15*** 20*** 3

Urolithiasis (%) 11 11 10

BMI: body mass index.* p < 0.05 (differences with control group).

** p < 0.01 (differences with control group).

*** p < 0.001 (differences with control group).

quantitative ultrasound index (QUI),and theestimatedbone min-

eral density (eBMD) of the calcaneus in g/cm2. Moreover, eBMD is

also reported based on its T-score. The European reference popu-

lation used for its calculation [31] yields results similar to those

obtained with the application of values from Spanish women, as

has been previously published [32]. Only one measurement was

also performed in each patient. In vivo short-term precision was

4.9% for BUA, 0.4 for SOS, 3.4% for QUI, and 4.1% for eBMD.

Quality controls were performed daily by scanning

manufacturer-provided phantoms.

2.5. Statistical analyses

Results were expressed as meanSD for quantitative variables

and percentages for qualitative variables. Data were analyzed for

normality, and,as appropriate, underwent logarithmic transforma-

tion. Chi-squared test or Fishers exact test was performed in order

to identify differences in categorical variables between groups.

Students t-testor MannWhitneyU-testwas used tocompare non-

categorical variables between the overall group of hypertensive

women and controls. One-way ANOVA with Bonferroni post hoc

test or KruskallWallis test were performed to analyze differences

among the threegroups of subjects included in the study hyperten-

sive women on thiazides, on other antihypertensive agents, andcontrols. Multiple stepwise linear regression models were con-

structed to adjust site-specific BMD and bone markers for age,

BMI, smoking habits, alcohol consumption, physical activity, dairy

calcium intake, history of falls in the previous year, diabetes, dys-

lipidemia, current -blockers and statin use, serum calcium, iPTH,25OHD, PINP and -CTX levels. All p-values 151mol/l), or because they wereon drugs known to affect bone metabolism. Of the remaining

636 women, 160 were receiving thiazide diuretics (hydrochloroth-

iazide: 12.550mg/day) for more than 1 year, due to hypertension,

whether alone (32 women) or in combination with other anti-

hypertensive agents (128 women), and 133 were only on

antihypertensive drugs other than thiazides (-blockers [25.6%],calcium channel blockers [15%], angiotensin converting enzyme

inhibitors or angiotensin receptor antagonists [66.2%], and loop

diuretics [37%]). Normotensive women who were not on thiazideor on other antihypertensive drugs were considered as the control

group(n = 343). The baseline characteristics of the study population

are listed in Table 1.

Hypertensive women on thiazides or on other antihypertensive

treatments were older than controls, and also had greater body

weight, BMI, and waist circumference values. Moreover, hyper-

tensive postmenopausal women had higher prevalence of diabetes

mellitus and dyslipidemia thancontrols. Conversely, current smok-

ing was less frequent in these patients. On the other hand, women

on thiazides reported a greater number of falls during the previ-

ous year, and both groups of hypertensive women showed a slight

non-significant higher number of fractures after 40 years of age

than controls. No differences in other risk factors for osteoporosis

or fractures were observed between either group of hypertensivewomen and controls (Table 1).

As previously indicated, most of hypertensive women treated

with thiazides were not on these agents alone, but received a com-

bination of several drugs. The percentage of patients treated with-blockers or calcium channel blockers, was similar in hyperten-sive women receiving thiazides and in those not receiving these

drugs (16.9%vs. 25.6% [p = 0.08] and 14.4% vs. 15% [p = 0.87], respec-

tively). However, current use of angiotensin converting enzyme

inhibitors or angiotensin receptorantagonistswas lower in patients

treated with thiazides (50.6% vs. 66.2%, p = 0.01).

The percentage of current statin users was also similar in both

groups of hypertensive patients (27.7% vs. 34.6%, p = 0.20); how-

ever, it was higher than in controls (13%, p < 0.0001 in both cases).

Serum glucose was higher in both groups of hypertensive women


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Table 2

Biochemical parameters in postmenopausal women on thiazides, on other antihypertensive agents, and in controls (mean SD).

Hypertensive women (N= 293) On t hiazides (N=160) On other anti-hypertensives (N= 133) Con tr ol group (N=343)

Glucose (mmol/l) 5.38 1.49*** 5.44 1.60*** 5.33 1.44** 4.94 0.72

Creatinine (mol/l) 88 14 88 14 88 27 85 20

Total cholesterol (mmol/l) 5.74 1.00* 5.71 1.00* 5.84 0.96 5.92 0.96

HDL-cholesterol (mmol/l) 1.45 0.36** 1.45 0.39* 1.47 0.39 1.53 0.39

LDL-cholesterol (mmol/l) 3.67 0.88** 3.65 0.88* 3.72 0.85 3.85 0.82

Triglycerides (mmol/l) 1.4 2 0.83** 1.39 0.82* 1.44 0.76* 1.21 0.64

Calcium (mmol/l) 2.43

0.10**

2.44

0.10**

2.43

0.10 2.41

0.09Phosphate (mmol/l) 1.16 0.11 1.13 0.11* 1.16 0.13 1.16 0.13

Albumin (g/l) 45 3 45 3 45 2 45 3

cCa (mmol/l) 2.31 0.09** 2.31 0.09** 2.30 0.09 2.28 0.08

Alkaline phosphatase (U/l) 72 20 70 17 75 22 71 19

25OHD (ng/ml) 23 8** 23 8* 23 9* 25 9

iPTH (pg/ml) 54 20* 55 21* 55 32* 51 23

P1NP (ng/ml) 43.0 21.3*** 41.9 20.8*** 44.6 21.3** 50.5 17.9

-CTX (ng/ml) 0.329 0.186*** 0.308 0.188*** 0.361 0.176* 0.411 0.184

cCa: albumin-corrected serum total calcium; 25OHD: 25-hydroxyvitamin D; iPTH intact parathyroid hormone; P1NP: aminoterminal propeptide of type I collagen; -CTX:

C-terminal telopeptide of type I collagen.* p < 0.05 (differences with control group).

** p < 0.01 (differences with control group).*** p < 0.001 (differences with control group).

comparedtothecontrolgroup(p < 0.01). Totalalkaline phosphatase

and creatinine levels were similar in women on thiazides or onother antihypertensive drugs as well as in the control group. Total

and albumin-corrected serum calcium were significantly higher

(p < 0.01) in the thiazide group than in controls. In the non-thiazide

hypertensive group, serum calcium levels were also higher than in

controls, but not significantly so. Serum iPTH was increased and

serum 25OD slightly, but significantly, decreased in both groups of

hypertensive women compared to controls (Table 2).

As expected, iPTH was negatively related with 25OHD levels

in each group (women on thiazides: r=0.215, p < 0.01; on other

antihypertensive drugs: r=0.368, p < 0.001; controls: r=0.314,

p < 0.001).

Regarding biochemical markers of bone remodeling, serum

P1NP and -CTX were significantly lower in hypertensive women

than in controls (Table 2). The decrease was more pronouncedamong thiazide users, in which a 17% and 25% decrease in serum

P1NP and -CTX levels, were observed, respectively (p < 0.001).Women on other antihypertensive drugs also have significantly

lower levels of both markers compared with controls, although in

this case changes were less pronounced (11% and 12%, respec-

tively; p < 0.05).

As shown in Table 3, BMD at the lumbar spine and hip

was higher in hypertensive women than in controls. Women

on thiazides had higher BMD at the lumbar spine (+3.8%;

p < 0.05) and at the femoral neck (+3.4%; p < 0.05) than con-

trols (Table 3). No significant differences were observed at the

total hip (+2.4%). However, when BMD was expressed as Z-score,

implying an age-adjustment, its values were higher at all levels

(Table 3). Women on antihypertensive agents other than thiazides

tended to show higher BMD values (expressed as g/cm2) at the

three sites, although differences did not reach statistical signif-

icance. When results were expressed as Z-score, BMD was also

higher at all bone locations (Table 3). Regarding QUS parame-

ters, no differences were found between patients on thiazides

(BUA: 64.818.9dB/mHz; SOS: 154032 m/sg; QUI: 87.919.7;

eBMD: 0.4790.125 g/cm2), other anti-hypertensives (BUA:

63.721.1 dB/mHz; SOS: 153934m/sg; QUI: 86.522.1; eBMD:

0.4720.140 g/cm2), and controls (BUA: 64.119.4dB/mHz; SOS:

154331m/sg; QUI: 87.419.9; eBMD: 0.4760.126 g/cm2).

Nevertheless, QUS and DXA measurements were significantly

related at any paired combination. The higher r values were

seen when total hip was one of the elements of the pair

(Table 4).

A stepwise multiple regression analysis was performed with

lumbar spine, femoral neck BMD and bone turnover markers asdependent variables, and age, BMI, smoking habits, alcohol con-

sumption, physical activity, dairy calcium intake, history of falls in

the previous year, diabetes, dyslipidemia, current -blockers andstatin use, serum calcium, iPTH, 25OHD, PINP and -CTX as inde-pendent variables, as previously stated. After adjustment, lumbar

spine BMDwas related with age, BMI, and thiazide use, butnot with

antihypertensive agents other than thiazides (Table 5). Thiazides

explainedabout 1%of the variabilityin lumbarspine BMD. Noinflu-

ence of thiazide use was noted regarding femoral neck or total hip

BMD. On the other hand, bone turnover markers were lower in

hypertensive women on treatment, although the difference was

greater in those on thiazides. After adjusting for confounders, dif-

ferences remained significant only in the thiazide group (data not

shown).

4. Discussion

In thepresent study we have compared BMDand bone turnover

markers in women with essential hypertension with those of

a control group, in the setting of a cohort of postmenopausal

women established to assess the prevalence of bone and calcium

metabolism disorders. Treated hypertensive women were divided

into two groups according to whether they were (or were not) on

thiazide treatment, irrespective of whether theywere also on other

antihypertensive drugs. The percentage of women on angiotensin

converting enzyme inhibitors or angiotensin receptor antagonists

was somewhat lower in women on thiazides than in those without

(50.6% vs. 66.2%), but no significant differences were found relatingto -blockers or calcium channel blockers. As expected, hyperten-sive womenwere older,had greater BMIandsuffered from diabetes

or dyslipidemia more frequently than those without hypertension.

BMD expressed as Z-score (which implies an adjustment for age)

was higher in both groups of hypertensive women at the three

measured levels (lumbar spine, femoral neck and total hip). BMD

expressed in absolute terms (g/cm2) was also higher in patients

on thiazides at the femoral neck and lumbar spine. Only the latter

difference remained significant after adjusting for potential con-

founding variables, including BMI. Bone turnover markers (both

P1NP and -CTX) were lower in the two groups of hypertensivewomen, although the difference was greater in those on thiazides.

Afteradjusting for potentialconfounders,differences remainedsig-

nificantonly in thethiazide group. Other differences found between


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Table 3

Comparisons of the BMD measured by DXA in the two study groups (mean SD).

Hypertensive women On thiazides On other anti-hypertensives Control group

LS (g/cm2) 0.926 0.132* 0.934 0.142* 0.922 0.123 0.898 0.132

T-score 1.38 1.20* 1.32 1.30* 1.43 1.12 1.62 1.20

Z-score 0.49 1.26*** 0.62 1.33** 0.38 1.17** 0.11 1.23

FN (g/cm2) 0.730 0.105 0.738 0.111* 0.727 0.109 0.713 0.115

T-score 1.65 1.05 1.57 1.10 1.68 1.09 1.80 1.16

Z-score 0.37 1.03*** 0.49 1.07** 0.30 1.04** 0.13 1.12

TH (g/cm2

) 0.874

0.114 0.871

0.122 0.874

0.112 0.850

0.126T-score 0.85 0.94* 0.87 1.01 0.85 0.93 1.04 1.05

Z-score 0.61 0.96*** 0.64 0.97** 0.57 0.97** 0.11 1.04

BMD: bone mineral density; LS: bone mineral density at the lumbar spine; FN: bone mineral density at the femoral neck; TH: bone mineral density at the total hip.* p < 0.05 (differences with control group).

** p < 0.01 (differences with control group).*** p < 0.001 (differences with control group).

Table 4

Relationship between QUS and BMD parameters in the whole population.

LS (g/cm2) FN (g/cm2) TH (g/cm2)

BUA (dB/mHz) 0.310* 0.287* 0.349*

SOS (m/sg) 0.312* 0.293* 0.353*

QUI 0.329* 0.316* 0.376*

eBMD (g/cm2) 0.331* 0.317* 0.375*

QUS:quantitative ultrasound; BMD:bone mineral density;LS: bonemineraldensityat the lumbar spine; FN: bone mineral density at the femoral neck, TH: bone min-

eral density at the total hip; BUA: broadband ultrasound attenuation. SOS: speed of

sound; QUI: quantitative ultrasound index; eBMD: estimated bone mineral density

of the calcaneus.* p < 0.0001.

patients on thiazides and controls were higher serum levels of cal-

cium and iPTH, and lower levels of 25OHD. Hypertensive women

on non-thiazide treatment also showed lower concentrations of

25OHD; serum levels of calcium and iPTH were higher than in

controls, but not significantly so.

Differences in bone and calcium metabolism between the non-

thiazide group and the control group are cancelled out after

adjusting for factors associated with both BMD and hypertension,

such as age or BMI. However, the differences between the thiazide

andcontrolgroup, besides beingmore pronounced than inthe non-

thiazide group, remain after adjustment, indicating that the drug

itself plays a role in this case. The possibility could also be enter-

tained that patients selected for treatment with the diuretic were

somehow different in nature from other hypertensive women, but

such a possibility seems very unlikely, since no important differ-

ences between them were observed regarding age, weight, glucose

and creatinine levels, statin treatment, etc. (see Tables 1 and 2).

The relationship between hypertension and bonemass has been

widely studied, although data have been inconclusive. In a cross-

sectional study, Hanley et al. [6] found that hypertension was

associated with higherBMD in womenand men, particularly at the

lumbar spine. However, Tsuda et al.[5] found that high blood pres-

sure was associated with reduced BMD in women, and Cappuccio

Table 5

Multivariate linear regression analysis (lumbar spine BMD [g/cm2] as a dependent

variable).a .

-Coefficient p

On thiazides 0.142 0.001

On other antihypertensive agent 0.062 0.15

BMI (kg/m2) 0.229


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decrease in bone turnover markers, in spite of higher serum PTH

levels, supporting the idea of a direct effect of thiazides on bone

[42,43].

No statistical significant changes were found in QUS measure-

ments in hypertensive women. To our knowledge, the relationship

between hypertension and QUS has not been previously studied.

Nevertheless, in a population-based study, van Daele et al. [19] did

not observe that treatment with thiazides affects ultrasound mea-

surements, an observation which is in agreement with our results.

Interestingly, a trend to a higher number of falls was seen in

hypertensive women, which reached a significant difference in the

case of women on thiazides. In addition, both groups of hyperten-

sive women showed a slightly higher number of fractures after 40

yearsof age,although thedifference wasnot significant.This coinci-

dence raises the possibility thatboth findingsare related, fallsbeing

a contributory factor for fracture development. There is no clear

reasonfor the increase infallsin hypertensive women,butthereare

a number of possible explanations that may be entertained, such

as episodes of hypotension in the case of drug overdose, or even

transient ischemic attacks. Diabetes is commoner in hypertensive

patients than in controls, and polyneuritis could also be consid-

ered. On the other hand, the greater number of fractures in patients

on thiazides is at contradiction with the supposed beneficial effect

of these drugs on bone mass. In dealing with this contradictionwe should take into account that the difference we have found,

although suggestive, is not significant. But if we accept that such

a difference may indeed be real, we have to consider, along with

the falls previously commented on, the possibility of bone quality

changes. For instance, coming backto the greater prevalence of dia-

betesin hypertensive patients,it has beenpointed out thatcollagen

glycosylation, through the pentosidine cross-links, may result in a

deterioration of bone quality and the corresponding fractures [44].

Our study has several limitations. As an observational study, it

is therefore subject to some possible bias due to confounding fac-

tors. However, adjustment for many potential confounding factors

such as age or weight has been carried out. In addition, obser-

vational studies often lack information on some details that may

be of some interest. In our case, we did not have precise infor-mation on the length of thiazide treatment. It could have been of

interest to relate this length with the effect of the drug on bone

metabolism. However, in real life, patients tend to follow treat-

ments somewhat irregularly, and therefore no precise therapeutic

periods may be defined. Therefore, we decided to ask for a year

of well followed treatment. By the same token, in everyday prac-

tice, some measurements are difficult to carry out, as it is the case

with 24h urine collections. Consequently, we do not have 24h uri-

nary calcium excretion values, which could have been interesting,

as they usually are when bone and mineral metabolism is studied.

Nevertheless, it is well known that thiazides interfere with urinary

calcium excretion. In our study, therefore, this parameter may not

be as important as in others.

In summary, we have found that hypertensive women on treat-ment with thiazides show higher BMD and lower bone turnover

markers than controls. Hypertensive women on treatments other

than thiazides show similar changes, although to a lesser extent.

Adjustingfor possible confounders, such as BMI, cancels out differ-

ences in non-thiazidetreatedpatients, but notin those on thiazides.

This suggests that,in thefirst group, such differences areaccounted

for by factors related to hypertension, of which overweight maybe

an example. However, the findings reported for the second group

seem to indicate that thiazides themselves are responsible for the

changes described in bone and calcium metabolism. Therefore, our

results add evidence to the idea that thiazides are beneficial to pre-

vent bone loss. This may be a factor to take into account when

choosing treatment among the several antihypertensive drugs,

especially in postmenopausal women at risk of osteoporosis.

Conflict of interest

No conflict of interest was declared.

Funding

This study was supported by grants from the Fondo de Inves-

tigacin Sanitaria, Ministerio de Sanidad y Consumo, Spain (FIS:

PI05 0125 and FIS: PI08 0183) and Instituto de Formacin eInvestigacin Marqus de Valdecilla, Santander, Spain (IFIMAV:

API/07/13).

Contributors

Jos M. Olmos: Conception, design, interpretation, and coor-

dination of the work, as well as to write the manuscript. Jos L.

Hernndez, Execution of the statistical analysis and interpreta-

tion of the study. Revision of the manuscript. Josefina Martnez:

Execution of biochemical studies and interpretation of the results.

Jess Castillo: Recruitment of subjects, interpretation of the study.

Carmen Valero: Execution of BMD and ultrasound studies and

interpretation of the results of the study. Isabel Prez Pajares:

Recruitment of subjects, interpretation of the study. Daniel Nan:Participation in recruitment o f subjects, and execution of BMD

studies. JessGonzlez-Macas: Conception, design, interpretation,

and revision of the manuscript.

Ethical approval

The study protocolwas approvedby thelocal EthicalCommittee.

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