Thyroid hormone treatment aiming at reduced, but not suppressed, serum thyroid-stimulating hormone levels in nontoxic goitre: effects on bone metabolism amongst premenopausal women

Do bone turnover markers reflect changes in bone microarchitecture during treatment of patients with thyroid dysfunction?

PURPOSE

This study aimed to compare changes in the bone turnover markers (BTMs)-C-terminal telopeptide of type I collagen (CTX-I) and procollagen I N-terminal peptide (PINP)-with changes in the bone microarchitecture, assessed by high-resolution peripheral quantitative computed tomography (HR-pQCT), during treatment of patients with thyroid dysfunction.

METHODS

In women with newly diagnosed hypo- or hyperthyroidism, HR-pQCT variables, obtained from the tibia and the radius, were compared with BTMs. Data were collected at diagnosis and after at least 12 months of euthyroidism.

RESULTS

73 women completed the study (hypothyroidism, n = 27; hyperthyroidism, n = 46). Among hyperthyroid patients, correlations were found between changes in BTMs and HR-pQCT variables, primarily for cortical variables in the tibia, i.e. cortical thickness (CTX-I, p < 0.001; PINP, p < 0.001), and volumetric bone mass density (vBMD) (CTX-I, p < 0.001; PINP, p < 0.001). Moreover, correlations between BTMs and estimated bone strength were found. In the hypothyroid subgroup, no significant findings existed after adjustment. Following treatment, less decrease in tibial vBMD was seen among patients with increasing CTX-I compared to those with a decreasing CTX-I level (p = 0.009). Opposite findings applied to PINP, as patients with decreasing PINP showed an increase in tibial vBMD, in contrast to a decline in this parameter among patients with increasing PINP (p < 0.001).

CONCLUSION

Changes in CTX-I and PINP correlated with HR-pQCT variables during the treatment of women with thyroid dysfunction. To some extent, these BTMs reflected the restoration of bone microarchitecture. CTX-I seems to be the most sensitive BTM in treatment-naïve thyroid diseases, while PINP is more useful for monitoring during treatment.

TRIAL REGISTRATION NUMBER

NCT02005250. Date: December 9, 2013.

Peripheral markers of thyroid function: the effect of T4 monotherapy vs T4/T3 combination therapy in hypothyroid subjects in a randomized crossover study

BACKGROUND

A recent randomized controlled trial suggests that hypothyroid subjects may find levothyroxine (l-T4) and levotriiodothyronine combination therapy to be superior to l-T4 monotherapy in terms of quality of life, suggesting that the brain registered increased T3 availability during the combination therapy.

HYPOTHESIS

Peripheral tissue might also be stimulated during T4/T3 combination therapy compared with T4 monotherapy.

METHODS

Serum levels of sex hormone-binding globulin (SHBG), pro-collagen-1-N-terminal peptide (PINP), and N-terminal pro-brain natriuretic peptide (NT-proBNP) (representing hepatocyte, osteoblast, and cardiomyocyte stimulation respectively) were measured in 26 hypothyroid subjects in a double-blind, randomized, crossover trial, which compared the replacement therapy with T4/T3 in combination (50 μg T4 was substituted with 20 μg T3) to T4 alone (once daily regimens). This was performed to obtain unaltered serum TSH levels during the trial and between the two treatment groups. Blood sampling was performed 24 h after the last intake of thyroid hormone medication.

RESULTS

TSH remained unaltered between the groups ((median) 0.83 vs 1.18 mU/l in T4/T3 combination and T4 monotherapy respectively; P=0.534). SHBG increased from (median) 75 nmol/l at baseline to 83 nmol/l in the T4/T3 group (P=0.015) but remained unaltered in the T4 group (67 nmol/l); thus, it was higher in the T4/T3 vs T4 group (P=0.041). PINP levels were higher in the T4/T3 therapy (48 vs 40 μg/l (P<0.001)). NT-proBNP did not differ between the groups.

CONCLUSIONS

T4/T3 combination therapy in hypothyroidism seems to have more metabolic effects than the T4 monotherapy.

Thyroxine suppression therapy for benign, non-functioning solitary thyroid nodules: a quality-effects meta-analysis

Levothyroxine (LT4) suppressive therapy for solitary thyroid nodules is not popularly advocated presently because its clinical efficacy and safety are currently considered controversial. This meta-analysis aims to address efficacy issues by using rigorous methods to arrive at a pooled estimate. On the basis of the analysis, it is estimated that LT4 therapy is clearly associated with up to a two-fold increase in the chance of nodule reduction. This translates to a number needed to treat (NNT) of 6 or a 50% decrease in the risk of cancer given nodule reduction. Keeping this definition of efficacy in mind and a low incidence of adverse events with low level LT4 suppression, such an intervention might be appropriate in patients selected on the basis of a low risk for adverse effects.

[Bone metabolism during substitution therapy of primary hypothyroidism]

INTRODUCTION

The relation between thyroid hormones and bone metabolism markers in hyperthyroidism is well known. Earlier studies indicate the possibility of bone metabolism acceleration during the excessive replacement therapy with l-thyroxin in hypothyroid patients especially in one with other risk factors for bone metabolism impairment. This study evaluated the effect of physiological l-thyroxine treatment on bone metabolism in patient with primary hypothyroidism.

MATERIAL AND METHODS

In the study group of 30 hypothyroid patients individual thyroxine replacement was performed targeting euthyroid status. Bone and calcium metabolism parameters (osteocalcin-OC, alkaline phosphates-ALP, C-terminal cross-linking telopeptide type l-CL, parathormone-PTH, Ca, ionized Ca, P), thyroid hormone levels (T3, T4, TSH) were measured before treatment and when euthyroid status was achieved.

RESULTS AND DISCUSSION

A significant treatment effect was observed for bone formation and resorption parameters before and during the therapy; OC (p = 0.000024), CL (p = 0.002648). Ionized calcium levels also showed significantly higher values in euthyroid status confirming bone metabolism acceleration during the l-thyroxine therapy (p = 0.020). Thus, calcium metabolism hormone regulators were not significantly different before and after the therapy; PTH (p = 0.27). Thyroid hormone levels showed significant correlation with bone metabolism parameters before the therapy whereas this correlation was not found during therapy because of different individual l-thyroxine doses.

CONCLUSION

It can be concluded that physiological doses of l-thyroxine therapy accelerate bone metabolism in hypothyroid patients. Thus, the argument against bone loss during physiological substitution is highly specific mutual correlation between bone formation and resorption parameters. These assumptions require further investigations in long-term prospective studies in patients on replacement l-thyroxine therapy.

The adaptation of TSH secretion to autonomy in non-toxic goiter may be based-on active regulation of set-point and sensitivity of central TSH-receptors, perhaps by the microRNA (MIR) gene

The hypothalamic-pituitary-thyroid (HPT) feedback system is one of the most complex regulatory systems and it has intrigued researchers for more than 50 years. One of the unsolved problems of this regulation in humans is the hypothalamic and pituitary adaption to autonomous function of the thyroid gland in non-toxic goiter (NTG). A new hypothesis, that TSH secretion is actively regulated in NTG in response to changes in thyroid autonomy in order to keep the patient euthyroid, was discussed in the present study on basis of previous experimental data in NTG patients with different degree of autonomous function. The patients were submaximally suppressed for one month with a fixed daily dose of T3. Group data suggested an inverse correlation between TSH suppression and suppression of thyroid function. Group data also suggested that TSH suppression was significantly correlated to basal TSH. This means that a NTG patient with a low normal TSH in blood before suppression (basal TSH) and a high degree of autonomous function may exhibit a relatively high TSH suppression. This ensures a minimal stimulation of the thyroid gland thereby protecting the gland from developing hyperthyroidism. A patient with a high normal TSH in blood before suppression (basal TSH) and a low degree of autonomous function, may exhibit a relatively low TSH suppression, indicating a high stimulation of the thyroid gland thereby protecting the patient from developing hypothyroidism. It is hypothesized that this adaption of TSH secretion to autonomy in NTG patients may be based on active regulation of both the set- point of the central TSH-receptors and the sensitivity of these receptors as well. Such an active regulation of the HPT axis may be controlled by one of the newly found post-transcriptional genes called MIR (microRNA).

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.

Assessment and Recommendations on Factors Contributing to Preanalytical Variability of Urinary Pyridinoline and Deoxypyridinoline

Background: Pyridinoline (PYD) and deoxypyridinoline (DPD) are two of the most extensively characterized biochemical bone markers, but the interpretation of results is hampered by biologic and other preanalytical variability. We reviewed factors contributing to preanalytical variation of pyridinium cross-links in urine.

Methods: We searched four databases for English-language reports on PYD and/or DPD in urine. Searches were restricted to humans, except for studies of stability, when the search was expanded to other species. The 599 identified articles were supplemented with references from those articles and with articles known to the authors.

Results: The mean reported within-day variability was 71% for PYD (range, 57–78%) and 67% for DPD (range, 53–75%). The mean interday variability was 16% for both DPD and PYD (range for PYD, 12–21%; range for DPD, 5–24%). The mean intersubject variabilities across studies were 26% for PYD (range, 12–63%) and 34% for DPD (range, 8–98%) for healthy premenopausal women and 36% (range, 22–61%) and 40%, (range, 27–54%) for postmenopausal women, respectively. Specimen instability and errors in creatinine measurements were additional sources of variability.

Conclusions: Intra- and intersubject variability can be reduced by collecting specimens at a specific time of the day and by maintaining similar patient status at each specimen collection regarding factors such as medications and dietary supplements.

Early changes in parameters of bone and mineral metabolism during therapy for hyper- and hypothyroidism

The effects of thyroid hormones on various organs and metabolic systems have been the focus of intensive research. In this study we investigated the mechanisms of the changes in some parameters of bone and mineral metabolism before and during treatment of hyper- and hypothyroidism. Our study groups were as follows; 1) Untreated hyperthyroid patients (n= 38), 2) Hyperthyroid patients treated for three months (n=21), 3) Untreated hypothyroid patients (n=27), 4) Hypothyroid patients treated for three months (n= 20), and 5) Euthyroid control subjects (age, weight, sex and menopausal status matched) (n = 47). As expected, the mean serum calcium (Ca), phosphorus (P), alkaline phosphatase (ALP), and urinary Ca/creatinine and deoxypyridinoline (D-Pyr)/creatinine levels were higher in group-1 than in the control group. Serum PTH level was lower in group-1 than in group-5. However, after treatment for three months (group-2) we found that the serum and urinary levels of these parameters (except ALP) were not different than in the control group. Group-3 and group-4 did not show any differences in these parameters compared with group-5. Covariance analysis showed that urinary D-Pyr excretion had a positive, independent relationship to the serum free T3 level and age (P < 0.001 and P = 0.02, respectively). These results suggest that both bone formation and resorption markers increase in hyperthyroid patients, and with the treatment, particularly, in the period of first three months the bone resorption markers decrease rapidly. If the treatment is maintained the decrease slows, becoming more gradual. However, bone formation markers like ALP remain high in hyperthyroid patients during the treatment. In the light of this data, it is possible to conclude that osteoblastic activity lasts longer in hyperthyroidism. On the other hand, we demonstrated that these bone formation and resorption markers do not seem to be different in hypothyroid patients, even during the treatment, compared to the euthyroid controls.

Effect of endogenous subclinical hyperthyroidism on bone metabolism and bone mineral density in premenopausal women

In this cross-sectional study, we evaluated 15 premenopausal women to elucidate whether bone turnover is increased and bone mineral density is reduced due to endogenous subclinical hyperthyroidism. Each patient had normal free thyroxine (FT4) and free triiodothyronine (FT3) levels associated with a stable suppression (<0.1 mU/L) of serum thyrotropin (TSH) levels during a period ranging between 6 and 11 months. Metabolic parameters of bone turnover (serum osteocalcin, bone specific alkaline phosphatase, procollagen I C-terminal peptide reflecting bone formation; urinary deoxypyridinoline and calcium excretion reflecting bone resorption) were assessed. Bone mineral density was measured at lumbar 1-4 vertebrae, femoral neck, and the forearm (midshaft radius and distal radius) by dual energy x-ray absorptiometry. All measurements were compared with 15 healthy age-, height-, and weight-matched premenopausal women who served as control group. Our findings suggest that endogenous subclinical hyperthyroidism is not associated with increased bone turnover, and bone mineral density is not reduced in premenopausal women, at least in the short term.