Urinary excretion of pyridinoline and deoxypyridinoline measured by immunoassay in hypothyroidism

Thyroid Hormones, Glucocorticoids, Insulin, and Bone

Several endocrine systems have important effects on bone tissue. Thyroid hormones are essential for normal growth and development. Excess of these hormones will result in clinically significant changes that may require intervention. Glucocorticoids also have a marked effect on bone metabolism by several pathways. Their endogenous or exogenous excess will induce pathological processes that might elevate the risk of fractures. Insulin and the carbohydrate metabolism elicit a physiological effect on bone; however, the lack of insulin (type 1 diabetes) or insulin resistance (type 2 diabetes) have deleterious influence on bone tissue.

[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.

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.

Bone formation and resorption biological markers in cosmonauts during and after a 180-day space flight (Euromir 95)

Long-term spaceflights induce bone loss as a result of profound modifications of bone remodeling, the modalities of which remain unknown in humans. We measured intact parathyroid hormone (PTH) and serum calcium; for bone formation, serum concentrations of bone alkaline phosphatase (BAP), intact osteocalcin (iBGP), and type 1 procollagen propeptide (PICP); for resorption, urinary concentrations (normalized by creatinine) of procollagen C-telopeptide (CTX), free and bound deoxypyridinoline (F and B D-Pyr), and Pyr in a 36-year-old cosmonaut (RTO), before (days −180, −60, and −15), during (from days 10 to 178, n = 12), and after (days +7, +15, +25, and +90) a 180-day spaceflight, in another cosmonaut (ASW) before and after the flight. Flight PTH tended to decrease by 48% and postflight PTH increased by 98%. During the flight, BAP, iBGP, and PICP decreased by 27%, 38%, and 28% respectively in CM1, and increased by 54%, 35%, and 78% after the flight. F D-Pyr and CTX increased by 54% and 78% during the flight and decreased by 29% and 40% after the flight, respectively. We showed for the first time in humans that microgravity induced an uncoupling of bone remodeling between formation and resorption that could account for bone loss.