Negative correlation between the change in bone mineral density and serum osteocalcin in patients with hyperthyroidism

Bone mineral metabolism and thyroid replacement therapy in congenital hypothyroid infants and young children

Impairment of calcium metabolism and low bone density have been found in hypothyroid adults. We investigated the effect of thyroid replacement therapy on calcium metabolism and bone mineralization in congenital hypothyroid (CH) infants and children. One hundred and 16 Caucasian CH consecutive patients were studied and were grouped according to their age: 23 patients at diagnosis, 20 at 3 mo, 24 at 6 mo, 25 at 12 mo and 24 at 36 mo. Thyroid replacement therapy was started at an initial dose of 6-8 micrograms/kg/day of L-thyroxine, and then decreased progressively. Calcium, phosphorus, magnesium, alkaline phosphatase (AP), parathyroid hormone (PTH) and osteocalcin (BGP) were measured as calcium metabolism indices. Bone mineral content (BMC) was measured at the mid-portion of the right radius AP, PTH and BGP concentrations were significantly higher in subjects at 3 mo of age (p < 0.05). This rise coincided with the end of the period of maximum dosage of L-thyroxine. Mild asymptomatic hypercalcemia was observed in 20 patients. All the other indices did not differ between age groups. BMC values and BMC annual increment were not different from those calculated for age-matched controls. We found that L-thyroxine replacement therapy does not alter bone mineralization of CH infants and children. Only a transitory increase of osteoblastic function was observed after the first few months of therapy.

Hip fractures and the thyroid: a case-control study

OBJECTIVE

To investigate the prevalence of thyroid illness - especially hyperthyroidism - and exposure to thyroid hormones in patients with hip fracture.

DESIGN

A case-control study.

SETTING

Two surgical/orthopaedic hospital units and 22 facilities for the aged in a moderately iodine-deficient region of Germany.

SUBJECTS

A total of 116 postmenopausal females with hip fracture and 402 postmenopausal female controls.

MAIN OUTCOME MEASURES

Hip fracture; thyroid disease confirmed by measurement of serum thyrotropin, total and free thyroxine and triiodothyronine; history of thyroid disease and thyroid medication obtained by a questionnaire.

RESULTS

Of the hip fracture patients 4.3% had overt untreated hyperthyroidism, and 6.9% gave a history of past hyperthyroidism (total, 11.2%). The corresponding figures for the controls were 2.0 and 2.7%, respectively (total, 4.7%). 7.8% of the cases had been exposed to levo-thyroxine for 3-29 years, compared to 11.2% of the controls. The odds ratio for hyperthyroidism (present and past) was 2.5 (1.2-5.3, 95% confidence interval), and the odds ratio for levo-thyroxine exposure was 0.67 (0.32-1.41) in the hip fracture patients.

CONCLUSIONS

Hyperthyroidism is found 2.5-fold more often in hip fracture patients than in controls. Hence, hyperthyroidism appears to be a significant risk factor for hip fracture and should be investigated by clinical and, when necessary, laboratory means in hip fracture patients. In contrast, no increased risk for hip fracture could be detected after exposure to levothyroxine.

Influence of clinical characteristics and parameters associated with thyroid hormone therapy on the bone mineral density of women treated with thyroid hormone

Reports of reduced bone mineral density (BMD) in patients receiving long-term replacement and suppression therapy with L-thyroxine have generated considerable interest and controversy. A substantial literature has evolved, with interpretation of conflicting results obscured by a variety of confounding factors. We examined the BMD measurements of 202 white women who were taking thyroid hormone to determine the contribution to BMD of a number of clinical characteristics and parameters associated with thyroid hormone therapy. Measurements of BMD (N = 335 over 2.6 +/- 1.6 years) of the spine (L2-L4) were performed in 195 subjects. The BMD of three sites of the hip was measured (N = 247 over 1.8 +/- 1.1 years) in 157 subjects. The BMD of the proximal radius was also measured (N = 172 over 1.8 +/- 1.2 years) in 124 subjects. Increasing age and a history of previous thyrotoxicosis had a deleterious effect on spine BMD. Body mass index (BMI) was positively correlated with spine BMD. Dose of thyroid hormone, duration of therapy, type of underlying thyroid disease, history of thyroidectomy, or serum-free thyroxine index did not influence either the initial BMD or the change in spine BMD over time. In the hip, age correlated with a decrease, and BMI with an increase in BMD. A history of previous thyrotoxicosis was associated with a decrease in hip BMD at all three sites (0.05 < p < 0.10). No other clinical parameters significantly influenced either the initial BMD or the change in hip BMD over time. Increasing age and dose of thyroid hormone, and a prior history of thyrotoxicosis had a deleterious effect on the BMD at the proximal radius. In summary, thyroid hormone therapy was not associated with a significant effect on BMD of the spine or hip, but a decreased BMD of the proximal radius was related to both previous thyrotoxicosis and to dose of thyroid hormone.

Hyperthyroidism, thyroid hormone therapy, and bone

Clinically symptomatic osteoporosis and fractures from thyrotoxicosis have been rare since the availability of antithyroid drugs and radioiodine for the treatment of hyperthyroidism. However, the widespread use of bone density measurements and sensitive TSH assays in the past decade has demonstrated that women taking levothyroxine with subclinical hyperthyroidism have reduced bone density. Cortical bone is affected more than trabecular bone, and postmenopausal women are at a greater risk than premenopausal women. However, it is uncertain whether subclinical hyperthyroidism is associated with an increased risk of fracture. Hypothyroidism is associated with an increase in cortical bone width. The initiation of levothyroxine treatment in hypothyroid women results in a reduction in cortical bone width to levels seen in euthyroid controls after 6-12 months. There is no reduction in bone density when women with subclinical hypothyroidism are treated with levothyroxine for a year. A single study showing reduced bone density in patients receiving chronic levothyroxine replacement therapy requires confirmation and raises an important question: Does levothyroxine replacement therapy, which results in higher serum thyroxine concentrations than those seen in euthyroid controls, accurately mimic physiology?

Change in bone mineral density in patients with hyperthyroidism after attainment of euthyroidism by dual energy X-ray absorptiometry

Because of the previous controversial findings in studies of bone mineral density in patients with hyperthyroidism with older methodologies, we assessed bone mineral density in 15 Japanese patients with Graves' disease (8 males and 7 females) before and after treatment using dual energy X-ray absorptiometry (DEXA). Bone mineral density of the lumbar vertebrae and the femur, and thyroid function, and several metabolic parameters were measured before treatment and again after patients achieved a euthyroid state following treatment with methimazole for 4 to 20 months (mean 10.6 months). The bone mineral density of patients was calculated as the percentage of the mean value (%BMD) in an age- and sex-matched control group, and correlations between the changes in bone mineral density and metabolic parameters before and after treatment were investigated. The %BMD of vertebrae in patients with Graves' disease before treatment was 89.7% of that found in the normal population. When patients became euthyroid after treatment, %BMD increased significantly to 94.9%, although it still remained below the control level. TSH receptor antibody, osteocalcin, and alkaline phosphatase were elevated before treatment, but decreased significantly after treatment. The change between pre- and posttreatment TSH receptor antibody was negatively correlated with the change in bone mineral density. In conclusion, these findings suggest that bone mineral density is decreased in patients with Graves' disease and that successful treatment of hyperthyroidism results in a significant increase in bone mineral density within a short period of time. Furthermore, TSH receptor antibody is a useful marker of changes in bone metabolism in this group of patients.

Bone mineral density in patients with endogenous subclinical hyperthyroidism: is this thyroid status a risk factor for osteoporosis?

OBJECTIVE

The aim of the present study was to elucidate whether endogenous subclinical hyperthyroidism due to a solitary autonomously functioning thyroid nodule affects bone metabolism and is a risk factor for osteoporosis.

DESIGN

In a cross-sectional study measurements of bone mineral density were performed in premenopausal and post-menopausal women. Patients were categorized into non-toxic nodular goitre (n = 32), subclinical hyperthyroid (n = 37) and toxic solitary autonomous thyroid nodule (n = 22) subgroups and the results were compared with those of sex and age-matched control reference population (n = 68).

MEASUREMENTS

Lumbar spine and femoral neck bone mineral densities were measured by dual energy X-ray absorptiometry. Single-photon absorptiometry was applied to the measurement of bone mineral content in the midshaft of the radius.

RESULTS

In the non-toxic nodular goitre group, bone densities for all the scanned sites did not differ from the sex and age-matched reference population. At the L2-4 scanning site a significant decrease in the bone mineral density could be observed only in the toxic nodular goitre group and this decrease was more marked in the postmenopausal (P < 0.001) than in the premenopausal females (P < 0.05). At the femoral neck and midshaft radius the mean densitometric values were slightly, but significantly, lower only in the post-menopausal subclinical hyperthyroid group compared with the reference population (P < 0.01). The bone mineral density of the femoral neck, as well as the bone mineral content of the midshaft radius, was significantly decreased in both the premenopausal and post-menopausal patients with a toxic solitary nodule.

CONCLUSION

This study indicates that the bone mineral density of the lumbar spine, femoral neck and the midshaft of the radius are not significantly decreased in premenopausal patients with endogenous subclinical hyperthyroidism resulting from a solitary autonomously functioning thyroid nodule. Conversely, findings hint at the possibility that long-lasting endogenous subclinical hyperthyroidism may be a contributing factor to the development of osteoporosis in some post-menopausal women, mostly at sites where cortical bone preponderates.

Bone mineral density in patients with hyperthyroidism measured by dual energy X-ray absorptiometry

OBJECTIVE

We assessed the changes of bone mass in patients with hyperthyroidism by measuring bone mineral density using a new method, dual energy X-ray absorptiometry.

DESIGN

The values of bone mineral density in patients with hyperthyroidism were compared with data obtained from the controls, and we assessed the correlation analysis between bone mineral density and several metabolic parameters.

PATIENTS

We studied 52 Japanese patients with hyperthyroidism (20 males, 32 females). Healthy normal subjects served to establish the mean bone mineral density in the healthy Japanese population (Shiraki et al. 1991).

MEASUREMENT

Bone mineral density was assessed by the measurement of lumbar vertebrae and femur by dual energy X-ray absorptiometry. The bone mineral density of vertebrae for each patient was calculated as the percentage of the mean value (% bone mineral density) obtained from an age and sex-matched control group. Blood was drawn to measure the levels of serum calcium, phosphorus, creatinine, alkaline phosphatase, free T3, free T4, TSH, TSH receptor antibody, parathyroid hormone, and serum osteocalcin.

RESULTS

The percentage bone mineral density of vertebrae in patients was 92.6 as compared with that of normal controls, and was inversely correlated with serum TSH receptor antibody, osteocalcin, and alkaline phosphatase.

CONCLUSIONS

These findings suggest that bone mineral density is decreased in patients with hyperthyroidism and that TSH receptor antibody, osteocalcin, and alkaline phosphatase are sensitive markers of bone metabolism alterations in hyperthyroidism.

Trabecular bone mineral density in primary hyperparathyroidism: relationship to clinical presentation and biomarkers of skeletal turnover

This study was carried out in order to investigate the entity of trabecular bone involvement in 62 patients with primary hyperparathyroidism (PHPT). Bone mineral density (BMD) was measured in all patients at the ultradistal radius (UDR) of the non-dominant arm by a dual photon densitometer and also at the lumbar spine (L) in 40 of the patients by means of quantitative dual energy radiography. Mean Z score values of UDR-BMD (-2.4 +/- 0.4) and L-BMD (-3.5 +/- 0.2) in patients with the skeletal variety of the disease (n = 6) were significantly reduced in respect to values of both asymptomatic (n = 31) and kidney stone patients (n = 25). As far as the comparison between the two sites of trabecular bone mass measurement in each hyperparathyroid subgroup of patients was concerned, a significant difference (P < 0.05) was found in patients with skeletal manifestations of the disease. Either serum total alkaline phosphatase activity, or osteocalcin and the 24-h hydroxyproline/creatinine ratio were significantly inversely related to the entity of bone mass evaluated at these two sites. Z score changes following surgery in 14 patients showed a positive trend in 13 of them at L compared to 7 out of 14 at UDR (P < 0.036 by chi square analysis). There was a very good inverse correlation between basal Z score values and the changes following surgery at the L (r = -0.851; P < 0.001) but not at the UDR. Our results demonstrate firstly that, in PHPT skeletal sites with almost similar composition of trabecular bone are differently involved in patients with more severe skeletal damage and that different skeletal sites may be divergently affected by the cessation of parathyroid gland hyperfunction.

Excessive L-thyroxine therapy decreases femoral bone mineral densities in the male rat: effect of hypogonadism and calcitonin

Excess thyroid hormone decreases bone mineral density (BMD), a potential problem in managing patients with differentiated thyroid carcinoma and nontoxic goiter who require lifelong TSH-suppressive doses of thyroid hormone. We studied the effect of thyroid hormone excess on vertebral and femoral BMD and the role of hypogonadism in modulating this effect in a rat model. The potential role of calcitonin (CT) in preventing thyroid hormone-associated bone loss was also investigated. A total of 40 male Sprague-Dawley rats were divided into four groups. Groups 1 and 2 were orchidectomized (ORX); groups 3 and 4 were sham operated (SO). Groups 1 and 3 received 20 micrograms intraperitoneal L-thyroxine (L-T4) per 100 g body weight daily for 3 weeks; groups 2 and 4 received vehicle IP. Another 40 rats were divided into four groups. Groups 1 and 2 received L-T4, and groups 1 and 3 received CT, 2.5 U per 100 g body weight, subcutaneously (SC) daily for 3 weeks. BMD of the L4 and 5 and the right femur were measured by dual-energy x-ray absorptiometry at baseline and at the end of the study. Orchidectomy decreased femoral (P < 0.05) but not lumbar BMD. The administration of excess L-T4 decreased femoral (cortical) BMD in both SO (P < 0.05) and ORX rats (P < 0.05) without affecting lumbar (trabecular) BMD. CT increased lumbar BMD in both vehicle (P < 0.001) and L-T4-treated rats (P < 0.001). However, CT did not affect femoral BMD in vehicle-treated rats and did not prevent the L-T4-induced femoral bone loss.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of oophorectomy on biochemical and bone variables in the rat

The metabolic effects of oophorectomy (Oophx) were studied in 6-month-old rats maintained on a normal chow diet. Nine weeks following operation, Oophx animals had a significantly lower femoral trabecular bone volume (BV/TV) than sham-operated animals; mean (SD) Oophx 8.5 (3.8)%; Sham 13.4 (2.5)%; P = 0.013). They also had a higher urine hydroxyproline (P less than 0.001), serum alkaline phosphatase activity (P less than 0.001), serum phosphate (P less than 0.001) and lower serum albumin (P less than 0.001) than the controls. Serum osteocalcin was inversely related to the BV/TV in the Oophx animals at 9 weeks post operation (r = -0.85, P = 0.007, n = 8). A fall in serum ionized calcium from 3 to 9 weeks post operation correlated with a fall in urinary hydroxyproline in the Oophx animals (r = 0.57, P = 0.002, n = 27). The data are consistent with a model of ovarian hormones acting directly to modulate bone cell activity as well as exerting an effect on the renal handling of phosphate.

Serum concentrations of osteocalcin in patients with hyperthyroidism, hypothyroidism and subacute thyroiditis

Serum concentration of osteocalcin (OC) was measured in sera from untreated patients with Graves' disease, hypothyroidism due to Hashimoto's thyroiditis, and subacute thyroiditis. Serum concentration of OC in Graves' disease and hypothyroidism were 14.1 +/- 5.6 micrograms/L and 3.8 +/- 2.7 micrograms/L, respectively which were significantly different from that of healthy subjects (Graves' disease, p less than 0.001, hypothyroidism, p less than 0.01). Serum concentration of OC in patients with subacute thyroiditis was 8.0 +/- 3.5 micrograms/L which was not statistically different from age-matched normal controls. Serial measurement of serum OC for 24 mo in 15 patients with Graves' disease after initiation of antithyroid drugs disclosed that the decline of serum OC was obtained only 24 mo after antithyroid drug therapy. On the other hand, in hypothyroid patients, increased serum OC was observed after 1-2 months treatment of L-T4. Correlation coefficients between serum concentrations of OC and T3, T4, FT3 or FT4 in all the patients with thyroid disorders were 0.66, 0.51, 0.50 and 0.54, respectively, which were statistically significant (all, p less than 0.001). These results suggest that osteoblastic activity is enhanced in hyperthyroidism and suppressed in hypothyroidism. In hyperthyroid patients, despite of normalization of FT4 concentration in relatively short period (within 3-4 mo), it took 24 mo after initiation of antithyroid drugs for OC to normalize, suggesting not only thyroid hormone per se but also some unknown factor(s) participates in serum OC secretion. In contrast to thyrotoxic patients, rapid increase in serum OC after initiation of supplemental L-T4 treatment in hypothyroidism was observed, suggesting a direct effect of thyroid hormone on the osteoblasts in patients with hypothyroidism.

Peripheral bone density in women with untreated multinodular goitre

OBJECTIVES

We wished to determine whether women with multinodular goitre and spontaneous subclinical hyperthyroidism have decreased bone density.

DESIGN AND SUBJECTS

Bone density was measured at the distal and proximal forearm. Data were expressed as Z-scores relative to the mean values out of 125 control subjects matched for age and menopause. The Z-scores of 23 women with subclinical hyperthyroid goitre (TSH < 0.1 mU/l and normal values for FT4 and total T3) and of 54 women with euthyroid goitre were compared.

MEASUREMENTS

Bone density was measured by single photon absorptiometry. TSH was measured by IRMA, FT4 by RIA.

RESULTS

Relative to the euthyroid goitre subjects the mean +/- SEM Z-scores of both the distal and proximal forearm density were lower (-0.69 +/- 0.17 vs -0.1 +/- 0.18, P < 0.05 and -0.5 +/- 0.18 vs 0.07 +/- 0.18, P < 0.05, respectively). Median (range) FT4 in the subclinical hyperthyroid goitre subjects was significantly higher than euthyroid goitre subjects (15.6 (11-23.2) pmol/l vs 11.9 (8.3-18.3) pmol/l, P < 0.001) although still within the normal range. FT4 correlated inversely with Z-scores of both distal and proximal forearm bone density in the subjects with subclinical hyperthyroidism (r = -0.42, P < 0.05 and r = -0.43, P < 0.05, respectively), but not in the euthyroid goitre subjects.

CONCLUSION

These findings indicate that women with untreated multinodular goitre and subclinical hyperthyroidism have reduced bone density in the forearm.

Determination of bone mineral density by quantitative computed tomography and single photon absorptiometry in subclinical hyperthyroidism: a risk of early osteopaenia in post-menopausal women

OBJECTIVE

There is evidence that treatment with L-thyroxine increases the risk of early osteopaenia. The aim of our study was to investigate the effect of subclinical hyperthyroidism in patients on TSH-suppressive L-thyroxine in view of the increased risk of decalcification.

DESIGN

Measurements of bone mineral density were performed in patients with subclinical hyperthyroidism at different scanning sites of varying trabecular portion. Bone mineral values as well as biochemical data were compared to those of normal controls.

PATIENTS

Fifty patients (nine men, 25 premenopausal and 16 post-menopausal women) on TSH-suppressive doses of L-thyroxine were investigated after removal of thyroid cancer.

MEASUREMENTS

Dual energy quantitative computed tomography was used for osteodensitometry in the lumbar spine. Single photon absorptiometry from a 125I source was applied to the calcaneus, midshaft radius and distal as well as proximal scanning sites of the distal radius. Normal bone mineral values for each measurement site were taken from healthy reference populations.

RESULTS

A significant decrease of bone mineral density in the calcaneus was found in 26 of 50 patients. Bone mass assessment yielded a 9.1% decrease of mean bone mineral content in all patients compared to controls (P less than 0.01). The decrease in post-menopausal women was 22% (P less than 0.001). In premenopausal women bone mineral density changes in the calcaneus were not statistically significant. Cortical measurement sites like the midshaft radius and the proximal scanning site of the distal forearm showed a 14.8% (P less than 0.05) and 10.8% (P = NS) decalcification in post-menopausal women but normal values at the distal scanning site. The lumbar spine was not affected by subclinical hyperthyroidism in either pre or post-menopausal women. In hypoparathyroid patients, bone density did not essentially differ from normals. There was no significant correlation between bone mineral values and duration of treatment or osteocalcin values.

CONCLUSIONS

Our data suggest that TSH suppressive L-thyroxine treatment has a detrimental effect on the appendicular skeleton in post-menopausal women. Additional effects of oestrogen deficiency and subclinical hyperthyroidism might lead to accelerated bone loss requiring close supervision to determine the smallest dose needed for suppression of the pituitary-thyroid axis.

Increased rat femur osteocalcin mRNA concentrations following in vivo administration of thyroid hormone

Thyroid hormone has a direct resorptive effect on bone. Thyroid hormone therapy in doses that suppress pituitary TSH production result in a reduction in bone density. Osteocalcin is a bone matrix protein. Serum levels are a sensitive marker for bone turnover and are increased in hyperthyroid patients. In order to establish an animal model to study the effects of thyroid hormone on bone turnover, we measured rat femur osteocalcin mRNA following in vivo administration of thyroid hormone. Young CD rats weighing 60-90 g were given daily ip injections of T3, T4, or saline (control) for 12 days. Blood was obtained for radioimmunoassays, and RNA was extracted from femurs and analyzed by Northern blot using a 60-mer synthetic oligonucleotide probe corresponding to bases 360-420 of rat osteocalcin mRNA, labeled with [32P] ATP by 5'-end-labeling. Serum TSH concentrations were suppressed to subnormal levels by the lowest doses of T3 and T4, and to undetectable levels by the higher doses. Increases in serum T3 and T4 concentrations were proportional to the dose of each administered hormone. T3, 5 and 10 micrograms/100 g body weight, resulted in a 43% and 62% increase in osteocalcin mRNA, respectively. T4, 5, 10, and 20 micrograms/100 g body weight, resulted in a 35%, 47%, and 135% increase in osteocalcin mRNA, respectively. These data demonstrate that in vivo administration of either T4 or T3 to young rats results in a significant dose-dependent increase in femur osteocalcin mRNA concentrations.

Osteocalcin: diagnostic methods and clinical applications

Osteocalcin is a small (Mr 5800), very interesting bone specific protein, synthesized by osteoblasts and measured in plasma as a biochemical indicator of bone formation. Many immunoassays for osteocalcin have been developed, including radio- and enzymoimmunoassays, with the use of monoclonal and polyclonal antibodies. These are used in many different clinical settings, including bone, kidney, and liver diseases. However, there is a wide range of published values for plasma osteocalcin concentrations in control and patient samples and this has hindered a more widespread adoption of osteocalcin measurement by clinicians. This review discusses how various immunoassays for osteocalcin may contribute to the wide variation of published values and suggests approaches for the development of standardized assays. For example, epitope specificity and immunoreactivity with multiple forms of osteocalcin and osteocalcin peptides in plasma are discussed. It also includes a recent update on interesting clinical applications of osteocalcin.