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

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.

The "Mechanostat" Principle and the Osteoprotegerin-OPG/RANKL/RANK System PART II. The Role of the Hypothalamic-Pituitary Axis

Recent literature provides us with the indication that the ratio of OPG/RANKL concentrations fluctuate in a non-linear (bell-shaped) mode, according to Frost's "mechanostat" theory, during the application of mechanical strain. A similar cellular signal transduction mechanism to mechanical loading, that may also regulate bone resorptive activities, has nowdays been proposed. Since the skeleton is considered to be an endocrine organ, as such, it may likewise be subject to hypothalamic control. This central regulatory system may continually modulate the adaptation of the bone homeostatic system to external challenges. The hypothalamic-pituitary-gonadal axis may play a role in the regulation of OPG/RANKL secretion. The "mechanostat" principle may well characterize the oscillatory properties of the signal transduction mechanism that controls hard tissue metabolism and includes biochemical apart from mechanical stimuli. J. Cell. Biochem. 118: 962-966, 2017. © 2016 Wiley Periodicals, Inc.

Metabolic and cardiovascular risk in patients with a history of differentiated thyroid carcinoma: A case-controlled cohort study

Hyperthyroidism seems to increase metabolic and cardiovascular risk, while the effects of sub-clinical hyperthyroidism are controversial. We evaluated metabolic and cardiovascular parameters in differentiated thyroid carcinoma (DTC) patients with suppressed thyrotropin (TSH) due to levo-thyroxine (L-T4) therapy. We studied DTC patients and, as a control group, patients with a history of surgery for non-malignant thyroid pathology. Significantly higher insulin and lower HDL-cholesterol levels were recorded in DTC subjects. In both groups, insulin levels were significantly related with body mass index (BMI) but not with age or L-T4 dosage. In DTC patients, a significant negative correlation was seen between HDL-cholesterol and BMI or L-T4 dosage. In both groups, intima-media thickness (IMT) correlated positively with age, BMI, glucose levels and systolic blood pressure. In DTC patients, increased IMT was significantly correlated with glycated hemoglobin (HbA1c), cholesterol and triglycerides. In DTC patients, C-reactive protein correlated positively with insulin, insulin resistance, triglycerides and systolic blood pressure, and negatively with HDL-cholesterol. In both DTC and control subjects, fibrinogen correlated positively with age, BMI, increased IMT, HbA1c and systolic blood pressure. In DTC subjects, plasma fibrinogen concentrations correlated positively with insulin resistance, cholesterol and LDL-cholesterol, and negatively with TSH levels. Our data confirm that the favorable evolution of DTC can be impaired by a high incidence of abnormal metabolic and cardiovascular data that are, at least in part, related to L-T4 therapy. These findings underline the need for adequate L-T4 titration.

The effects of recombinant TSH on bone turnover markers and serum osteoprotegerin and RANKL levels

OBJECTIVE

Recently it was found that thyrotropin (TSH) receptors are present both in osteoclast and osteoblast and that TSH can modulate bone remodeling independent of thyroid hormones. The aim of this study was, firstly, to evaluate the effects of acute administration of TSH on bone remodeling markers both in men and in women and, secondly, to evaluate if these effects are mediated by variations in serum osteoprotegerin (OPG) and receptor activator of nuclear factor-KB ligand (RANKL).

DESIGN

We studied 30 thyroidectomized patients (10 premenopausal and 10 postmenopausal women, 10 men) affected by thyroid carcinoma on l-thyroxine therapy. Eighty age- and sex-matched subjects were used as controls. A blood sample was drawn from each patient at baseline and 3 and 5 days after recombinant human TSH (rhTSH) administration, in preparation for (131)I whole body scan, to assess serum bone markers and serum OPG and RANKL levels.

MAIN OUTCOME

At baseline, postmenopausal women and men had significantly higher values of bone turnover markers and serum OPG compared to control subjects. In all thyroidectomized patients serum RANKL was lower than in controls. After rhTSH administration, serum N-terminal propeptide of type-I procollagen (PINP), a marker of bone formation, increased significantly in postmenopausal women, while serum RANKL significantly increased after 3 days in postmenopausal patients and men returning to baseline values at day 5. Serum OPG levels did not change significantly.

CONCLUSIONS

The low serum TSH observed in thyroidectomized patients on l-thyroxine therapy is associated with an increase of bone turnover in postmenopausal women and men that is associated with an increase of OPG and a decrease of serum RANKL levels. The acute TSH administration results in an increase of PINP, an index of osteoblastic activity, associated with an increase of serum RANKL. The lack of this response in premenopausal women suggests an influence of estrogen status on bone reactivity to TSH.

OPG, RANK and RANK ligand expression in thyroid lesions

Receptor activator of NF-kappaB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG) play essential roles in bone metabolism. RANKL binds to RANK, which is expressed by osteoclasts whereas OPG acts as its decoy receptor blocking the RANK-RANKL interaction. OPG/RANK/RANKL are produced by variety of tissues including epithelial and mesenchymal cells. However, the role of RANKL/OPG in thyroid pathophysiology remains unclear. The aim of this study was to determine the expression pattern of RANK/RANKL/OPG in primary neoplastic thyroid lesions and in lymph node metastases. 27 specimens from total thyroidectomy were studied by immunohistochemistry: 9 papillary carcinomas (PC), 9 medullary carcinomas (MC), 9 macrovesicular adenomas (MA). Immunohistochemical evidence of RANKL was found in 30 % of MC, 22% of PC while RANKL has never been detected in PC. The expression of RANK is closely related to RANKL. OPG was restricted to the cytoplasm of epithelial in 1 MA and 1 MC. In contrast to pathological tissues, any expression of OPG/RANK/RANKL was detected in healthy thyroid tissue. This work reveals for the first time that OPG/RANK/RANKL are expressed in the pathological thyroid gland by follicular cells, by malignant parafollicular cells as well as in metastatic lymph node microenvironment. Thus OPG/RANK/RANKL molecular triad might play a role during pathogenesis of follicular and parafollicular tumors.

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.