Suppressive levothyroxine therapy has no significant influence on bone degradation in women with thyroid carcinoma: a comparison with other disorders affecting bone metabolism

Endocrine Regulation on Bone by Thyroid

BACKGROUND

As an endocrine organ, the thyroid acts on the entire body by secreting a series of hormones, and bone is one of the main target organs of the thyroid.

SUMMARY

This review highlights the roles of thyroid hormones and thyroid diseases in bone homeostasis.

CONCLUSION

Thyroid hormones play significant roles in the growth and development of bone, and imbalance of thyroid hormones can impair bone homeostasis.

Risk of osteoporosis in thyroid cancer patients using levothyroxine: a population-based study

BACKGROUND

The outcomes of thyroid cancer patients using levothyroxine are largely undetermined.

METHODS

The study population consisted of 9398 patients newly diagnosed with thyroid cancer; their data was retrieved from a subset of the National Health Insurance Research Database of Taiwan during the period of 1999-2011. In this nationwide retrospective cohort study, we compared the risk of osteoporosis among thyroid cancer patients with levothyroxine use, those without levothyroxine use, and propensity-score-matched non-thyroid controls. We also investigated the duration-response and dose-response relationships between levothyroxine use and the risk of osteoporosis. The competing risk was also analyzed.

RESULTS

The mean duration of follow-up was 6.63 years for patients without thyroid cancer, 5.45 years for thyroid cancer patients without levothyroxine use, and 6.46 years for thyroid cancer patients with levothyroxine use. The incidence of osteoporosis was higher in the thyroid cancer cohort than in the non-thyroid-cancer cohort (8.69 vs. 6.60 per 1000 person-years, respectively), with an adjusted hazard ratio of 1.39 (95% confidence interval [CI] = 1.22-1.58). Thyroid cancer patients with levothyroxine use exhibited a significantly higher risk of osteoporosis than non-thyroid-cancer patients, while thyroid cancer patients not using levothyroxine did not have significant higher risks than non-thyroid-cancer patients. Compared with patients without thyroid cancer, the risk of osteoporosis increased from 1.53 (95% CI = 0.91-2.57) in patients receiving a cumulative dose of ≤265 mg levothyroxine, to 3.62 in those receiving a cumulative dose of >395 mg levothyroxine (95% CI = 2.16-6.06).

CONCLUSION

Our population-based cohort study showed that thyroid cancer patients receiving levothyroxine have a higher risk of osteoporosis.

Long-term treatment-related morbidity in differentiated thyroid cancer: a systematic review of the literature

Background

Differentiated thyroid cancer (DTC) occurs in relatively young patients and is associated with a good prognosis and long survival. The management of this disease involves thyroidectomy, radioiodine therapy, and long-term thyroid-stimulating hormone suppression therapy (THST). The long-term effects of the treatment and the interaction between subclinical hyperthyroidism and long-term hypoparathyroidism are poorly understood. This review sought to examine the available evidence.

Methods

A PubMed search was carried out using the search terms “Thyroid Neoplasms” AND (“Thyroxine” OR “Hypocalcemia” OR “Thyrotropin”). Original English language articles published in the last 30 years studying the morbidity from thyroid-stimulating hormone (TSH) suppression and hypoparathyroidism following a surgery for DTC were retrieved and reviewed by 2 authors.

Results

Of the 3,000 results, 66 papers including 4,517 patients were selected for the present study. Studies reported on a range of skeletal (included in 34 studies, 1,647 patients), cardiovascular (17 studies, 957 patients), psychological (10 studies, 663 patients), and other outcomes (10 studies, 1,348 patients). Nine of 26 studies on patients who underwent THST showed a reduction in bone density, and 13 of 23 studies showed an increase in bone turnover markers. Skeletal effects were more marked in postmenopausal women. There was no evidence of increased fracture risk, and only little data were available on hypoparathyroidism. Four of five studies showed an increased left ventricular mass index on echocardiography, and one study showed a higher prevalence of atrial fibrillation (AF). There was little difference in basic physiological parameters and limited literature regarding symptoms or significant events. Six studies showed associations between long-term TSH suppression and impaired quality of life. Impaired glucose metabolism and prothrombotic states were also found in DTC patients.

Conclusion

There is limited literature regarding long-term DTC treatment-related morbidity, particularly regarding the effects of long-term hypocalcemia. Most studies have focused on surrogate markers and not on clinical outcomes. A large prospective study on defined clinical outcomes would help characterize the morbidity of treatment and stimulate research on tailoring treatment strategies.

Bone mineral density and bone turnover markers in patients on long-term suppressive levothyroxine therapy for differentiated thyroid cancer

Purpose

Current management for patients with differentiated thyroid cancer includes near total thyroidectomy and radioactive iodine therapy followed by administration of supraphysiological doses of levothyroxine (L-T4). Although hyperthyroidism is a well known risk factor for osteoporosis, the effects of L-T4 treatment on bone mineral density (BMD) in patients with thyroid cancer do not appear to be as significant as with endogenous hyperthyroidism. In this study, we evaluated the impact of long-term suppressive therapy with L-T4 on BMD and bone turn over markers in Korean female patients receiving L-T4 suppressive therapy.

Methods

We enrolled 94 female subjects (mean age, 50.84 ± 11.43 years) receiving L-T4 after total or near total thyroidectomy and radioactive iodine therapy for thyroid cancer (mean follow-up period, 12.17 ± 4.27 years). The subjects were divided into three groups by thyroid stimulating hormone (TSH) level (group 1 with TSH level ≤0.001 µIU/mL, group 2 with TSH level between 0.001 and 0.17 µIU/mL, group 3 with TSH level >0.17 µIU/mL) and four groups by quartile of free T4 level. L-T4 dosage, BMD (examined by dual-energy x-ray absorptiometry), and bone turnover markers were evaluated according to TSH and free T4 levels.

Results

No significant decrease was detected in BMD or bone turnover markers according to TSH level or free T4 level. Also, the prevalence of osteoporosis and osteopenia was not different among groups.

Conclusion

Long-term L-T4 suppressive therapy after thyroid cancer management did not affect bone density or increase the prevalence of osteoporosis even though TSH levels were supraphysiologically suppressed.

Bone demineralization in postmenopausal women: role of anamnestic risk factors

This study evaluated the effects of LT4 administration on the bone mineral density (BMD) in physiological postmenopausal women after two years of continuative treatment. 110 postmenopausal women with nodular goiter aged between 50 and 55 years were examined before and after 2 years of therapy with a fixed dose of LT4 (1.6 mcg/kg/die) for the treatment of nodular thyroid disease. The results showed that the patients on treatment with LT4 have a slight, but significant reduction of the BMD after 2 years of treatment, associated with increased serum levels of alkaline phosphatase and urinary excretion of hydroxyproline, confirming our data conducted on the same group after one year of therapy. Comparison between patients receiving LT4 (group A) or not (group B) showed that group A patients had significantly lower BMD. We demonstrated the statistically significant influence of the following risk factors on BMD: (1) body mass index <19 kg/m(2); (2) the onset of menarche after the age of 15 years; (3) positive history for period of amenorrhoea; (4) nulliparity.

High cathepsin K levels in men with differentiated thyroid cancer on suppressive L-thyroxine therapy

BACKGROUND

Thyroid hormone administration is associated with low bone density in some studies. The aim of the present study was to evaluate the influence L-thyroxine, in doses used to treat patients with a history of thyroid carcinoma, on serum cathepsin K and other markers of bone metabolism. Cathepsin K is thought to have a role in osteoclast mediated bone resorption.

METHODS

A group of male patients with differentiated thyroid cancer (DTC) on suppressive L-thyroxine therapy (DTC-group; n = 51; mean age 57 years; TSH < 0.1 mU/L) was selected as a model for hyperthyroidism. The results were compared to a group of healthy euthyroid men (control-group; n = 50; mean age 58 years; TSH 1.5 +/- 0.9 mU/L).

RESULTS

In the DTC-group the median value of cathepsin K was 6.9 pmol/L, in the control group 4.8 pmol/L (p = 0.0052; highly significant [h.s.]). There was a significant negative correlation of cathepsin K with age (r = -0.279, p = 0.028). The analysis of various bone associated parameters revealed an increase of serum crosslaps in the DTC-group versus euthyroid controls (p = 0.03). A significant correlation could be found for cathepsin K and osteoprotegerin (p = 0.002).

CONCLUSION

Cathepsin K is increased by a suppressive L-thyroxine therapy and decreases with increasing age. The increased cathepsin K levels seen in DTC-patients on suppressive L-thyroxine therapy are likely to contribute to accelerated bone degradation in these patients.

Thyroid and bone

This article provides a summary of the numerous interactions between the thyroid gland and the skeleton, in the normal state, in disorders of thyroid function and as a result of thyroid malignancy. It recaps the current understanding of bone growth and development in the endochondral growth plate and the normal mechanisms of mature bone remodeling. The actions of thyroid hormones on these processes are described, and the clinical impact of thyroid disorders and their treatments on the bone are summarized. Finally, our current understanding of the physiology of bone metastases from thyroid cancer is covered.

Receptor activator of nuclear factor kappaB ligand and osteoprotegerin in men with thyroid cancer

BACKGROUND

Suppressive thyroid hormone therapy is generally a lifelong treatment for patients with differentiated thyroid cancer (DTC). However, long-standing thyrotropin (TSH) suppression is a risk factor for osteoporosis. Osteoprotegerin (OPG) and receptor activator of nuclear factor kappaB ligand (RANKL) are central regulators of bone turnover. The aim was to analyze the effects of a suppressive thyroid hormone therapy in males with DTC on the OPG/RANKL system and on bone metabolism.

PATIENTS AND METHODS

The OPG and soluble RANKL (sRANKL) were determined in 40 men (mean age, 53.2 years) with DTC on suppressive thyroid hormone therapy (TSH; 0.053 +/- 0.037 mU L(-1), duration 5.7 +/- 4.4 years) and 120 healthy controls matched for age. The markers of bone metabolism were C-terminal telopeptide of type I collagen in serum (sCTx) and osteocalcin (OC).

RESULTS

The control group had OPG values (mean +/- SD) of 1.9 +/- 1.0 pmol L(-1) and sRANKL values of 0.40 +/- 0.62 pmol L(-1). In patients with DTC, results for OPG were 3.03 +/- 1.04 pmol L(-1) (P < 0.05) and for sRANKL were 0.13 +/- 0.16 pmol L(-1) (P < 0.05). The control group presented values for sCTx of 2669 +/- 1132 pmol L(-1) and for OC of 17.89 +/- 6.5 ng mL(-1). Patients with DTC on suppressive thyroid hormone therapy had increased sCTx values of 3810 +/- 2020 pmol L(-1) (P = 0.03) but comparable OC values of 19.21 +/- 7.67 ng mL(-1) (NS).

CONCLUSIONS

Suppressive thyroid hormone therapy in men with DTC increased bone degradation and induced significant changes in the OPG/RANKL system. These changes include, besides the risk of osteoporosis, possible negative effects on the vascular function and an increased risk of cardiovascular disease.

Changes of bone mineral density in pre-menopausal women with differentiated thyroid cancer receiving L-thyroxine suppressive therapy

OBJECTIVE

We studied the effect of levothyroxine (L-T(4)) suppressive therapy on bone mineral density (BMD) in pre-menopausal women with total thyroidectomy and radioactive iodine ((131)I) ablation therapy post-operatively for differentiated thyroid cancer (DTC).

PATIENTS AND METHODS

We prospectively studied 26 athyroid pre-menopausal women (median age 39 years, range 28-48 years) receiving suppressive L-T(4) therapy postoperatively for 48 months. BMD was measured by dual energy X-ray absorptiometry (DEXA) at the femoral neck, femoral trochanter and Ward's triangle, before (basal) and during (12th and 48th month) the follow-up period. None of the women gave a medical history that could possibly affect bone metabolism. Patients were free of thyroid cancer in clinical and laboratory examinations at the time of the study. Paired t-test was used for comparisons among BMD measurements during the suppressive therapy.

RESULTS

There were statistically significant decreases of BMD at all measured regions during (12th and 48th month) L-T(4) suppressive therapy. The overall decreases in BMD at the femoral neck, femoral trochanter and Ward's triangle were 7.5%, 10.9% and 3.4%, respectively, at the end of the follow-up period. The coefficient of variation (CV) of all BMD measurements was around 10%, showing a rather homogenous group of patients. Our patients had a statistically significant decrease in their body mass index (BMI) and weight at the end of the follow-up period. However, there was no significant correlation between the decrease in BMI and BMD. Patients did not experience significant adverse effects from L-T(4) suppressive therapy during the study.

CONCLUSION

L-T(4) suppressive therapy for at least 1 year in pre-menopausal women with DTC causes a reduction in BMD of the femoral neck, femoral trochanter and Ward's triangle.

The effects of thyrotropin-suppressive therapy on bone metabolism in patients with well-differentiated thyroid carcinoma

Patients with differentiated thyroid carcinoma (DTC) are commonly treated long-term with thyrotropin (TSH)- suppressive thyroxine replacement therapy resolving in a state of subclinical hyperthyroidism. The relationship between subclinical hyperthyroidism and osteoporosis is not clear. In this review, we systematically selected and analyzed 21 studies addressing this issue. Although multiple methodological differences between studies prevented a structured meta-analysis, our data suggest that postmenopausal women with subclinical hyperthyroidism are most at risk, whereas no increased risk was observed in men and premenopausal women. Based on these findings we believe that measurement of bone mineral density is recommended in postmenopausal women with DTC starting TSH suppressive therapy. This should be subsequently regularly measured to enable timely intervention with bone protective agents.

Effects on Bone Mineral Density by Treatment of Benign Nodular Goiter with Mildly Suppressive Doses of L-Thyroxine in a Cohort Women Study

OBJECTIVES

Thyroid diseases and their treatment may influence the osseous system. The influence that prolonged suppressive L-thyroxine (LT4) therapy may have on inducing subclinical hyperthyroidism on bone metabolism is still a matter of debate. The aim of the present study was to assess the effects of chronic LT4 treatment at mildly inhibiting serum thyroid-stimulating hormone (TSH) doses on bone mineral density (BMD) and biochemical bone remodeling markers in a cohort of women with benign nodular goiter, and to verify the efficacy of the treatment on nodule size.

SUBJECTS AND STUDY DESIGN

A total of 200 euthyroid Caucasian women with nodular goiter (age 52.1 +/- 9; 80 pre- and 120 postmenopausal) were enrolled: 96 had been treated with LT4 for at least 3 years and a matched group of 104 had untreated goiter. LT4 therapy was given at a dose sufficient to reduce TSH under the lower limit of the normal range (0.27-4.20 microIU/ml) without suppressing it below the limit of assay sensitivity (0.005 microIU/ml) and maintaining normal serum values of free triiodothyronine (FT3) and free thyroxine (FT4). The adequacy of the dose was evaluated on the basis of serum TSH levels. The osteopenic effect of LT4 treatment was evaluated directly by total body and lumbar spine dual-energy X-ray absorptiometry (DEXA) and indirectly by biochemical parameters (alkaline phosphatase, osteocalcin, calcium, parathyroid hormone) at the baseline and throughout the follow-up. The efficacy of LT4 schedule on thyroid nodule size was assessed on the basis of the ultrasonographic evaluation.

RESULTS

Mineralometric data showed no significant difference between BMD values for treated and untreated patients in both pre- and postmenopausal status. In all patients, serum markers of bone turnover were in the normal range, with no differences in the treated and control groups. The TSH concentrations were significantly lower in treated than in untreated patients (p < 0.0001); FT3 and FT4 were in the normal range for all patients. Evaluation of nodule size during follow-up showed a reduction of > or = 30% in 32 of 96 treated patients (33.3%) versus none in those untreated, whilst nodule size remained unmodified in 60 treated patients (62.5%) versus 35 (33.6%) in those untreated, and an increase in nodule size and/or development of new nodules was found in 4 treated patients (4.2%) versus 69 of the 104 untreated patients (66.3%).

CONCLUSIONS

This study suggests that at slightly suppressing TSH doses, LT4 therapy has no adverse effects on BMD in both pre- and postmenopausal women, while having an efficacy on nodule size comparable with that reported using an LT4 schedule able to maintain TSH near or below the assay sensitivity limit.

Modern Management of Differentiated Thyroid Cancer

The outcome in differentiated thyroid cancer is excellent. Simple prognostic factors, including the age of the patient at diagnosis, the size of the primary cancer, completeness of surgical excision, and the presence of distant metastases, allow the clinician to judge how a patient will do. The preferred treatment is total thyroidectomy and in selected patients radioactive iodine can be used to ablate residual thyroid or functioning metastases in lymph nodes and distant sites. The physician has two excellent methods for following the patient: the whole-body scan with radionuclides of iodine, and measurement of serum thyroglobulin. In patients with elevated thyroglobulin and negative scans with radioactive iodine, there is increasing evidence that positron emission tomography (PET) is helpful in locating the site of thyroglobulin production.

Bone metabolism in patients with differentiated thyroid carcinoma receiving suppressive levothyroxine treatment

AIM

Patients with differentiated thyroid carcinoma (DTC) must receive suppressive levothyroxine (LT(4)) therapy for the rest of their lives. The literature, however, presents conflicting results on how this affects bone metabolism. The aim of this study was to assess the influence of the estrogen status and LT(4) therapy, in particular LT(4) dosage in micrograms per kilograms (microg/kg), on bone metabolism in female patients with DTC.

MATERIAL AND METHODS

Three markers of bone metabolism (C-terminal telopeptide of type I collagen in serum [SCTx]; N-terminal telopeptide of type I collagen in urine [U-NTx]; and osteocalcin [OC]) were investigated in four groups: group REF (healthy premenopausal female controls), group DTC-ES (premenopausal women with DTC and normal estrogen levels), group DTC-ED (postmenopausal women with DTC and estrogen deficiency), and group DTC-HRT (postmenopausal women with DTC undergoing hormone replacement therapy [HRT]). All patients with DTC were on a well-adjusted suppressive LT(4) therapy with TSH levels 0.1 mU/L or less.

RESULTS

In group DTC-ES bone turnover was comparable to group REF, whereas in group DTC-ED, all three markers were significantly increased as compared to groups REF and DTC-ES. In group DTC-HRT, the HRT normalized U-NTx and OC. However, in this group S-CTx was not completely normalized by HRT in all patients, although also significantly lowered compared to group DTC-ED. The analysis of LT(4 )dosage per kilogram showed that premenopausal DTC-patients had increased markers of bone metabolism if LT(4) dosage exceeded 2.6 microg/kg. Estrogen-deficient patients with DTC, however, had a much lower critical LT(4) dosage, above which increased markers of bone metabolism were seen.

CONCLUSION

A well-adjusted suppressive LT(4) therapy of less than 2.6 microg/kg and normal estrogen levels do not seem to increase bone metabolism in estrogen-sufficient patients with DTC. The normalization of an estrogen deficiency by HRT or other antiresorptive therapies and minimal suppressive dosages of LT(4) are attempts to optimize the care of patients with DTC. In postmenopausal patients with DTC and patients with DTC who require LT(4) dosages in excess of 2.6 microg/kg, the information provided by markers of bone metabolism may help to prevent bone damage.

Treatment of benign nodular goitre with mildly suppressive doses of L-thyroxine: effects on bone mineral density and on nodule size

OBJECTIVES

To evaluate (i) the demineralizing effect of L-thyroxine (LT4) therapy at doses mildly inhibiting serum thyroid stimulating hormone (TSH) in patients with benign nodular goitre; (ii) the efficacy of treatment on nodule size.

DESIGN

Cross-sectional study comparing euthyroid women with nodular goitre treated with LT4 for > or = 2 years (52 +/- 32 months, range 24-138, median 42) and a matched group with untreated goitre.

SUBJECTS

A total of 89 female outpatients (53.3 +/- 9 years; 36 pre- and 53 postmenopausal), 43 treated and 46 untreated.

MAIN OUTCOME MEASURES

Bone mineralization was measured with total body and regional mineralometry [dual energy X-ray absorptiometry (DEXA)], and indirectly evaluated with biochemical parameters (alkaline phosphatase, osteocalcin). Efficacy of LT4 therapy was assessed by measuring the nodule size during ultrasonography. The adequacy of the treatment was evaluated on the basis of serum TSH levels.

RESULTS

No significant differences were found at DEXA for total body and regional mineralization (P > 0.05 for all comparisons) in treated and untreated patients, both in pre- and postmenopausal states. Evaluation of the nodule size during the ultrasound scan showed a reduction of > or = 30% in 11 of 43 treated patients (26%) versus none of the untreated, an unchanged size in 29 treated patients (67%) versus 18 untreated, an increase of nodules and/or new nodule development in three treated patients (7%) versus 28 untreated (61%).

CONCLUSIONS

L-thyroxine (LT4) treatment at doses slightly suppressing TSH does not significantly affect bone mineralization, nor does it represent a risk factor for osteoporosis, even in postmenopausal patients. The efficacy of this therapeutic schedule on goitre size is comparable with the effects previously reported with suppressive doses.