Keywords
osteoporosis - hormones - estradiol - calcitonin - parathyroid hormone
Introduction
Osteoporosis results from an imbalance in normal bone metabolism between osteoblasts and osteoclasts.[1] Osteoclasts seem more active than osteoblasts in bone resorption processes.[2]
[3] Studies indicate that hormones may play an important role in imbalanced bone formation,[4] since parathyroid hormone apparently induces osteocytes differentiation into osteoclasts.[5] Likewise, hormones such as estradiol and testosterone are supposedly important,[6]
[7]
[8] and testosterone acts by inhibiting osteoblast apoptosis.[9] On the other hand, estrogen seems critical to bone remodeling both in males and females, since it apparently stimulates calcitonin release and activates intestinal vitamin D receptors, resulting in endocrine and immune functions during bone metabolism.[10]
[11] Calcitonin and vitamin D help to maintain adequate serum concentrations of calcium to allow normal bone mineralization. In addition, vitamin D is required for bone growth and remodeling by osteoblasts and osteoclasts.[12]
The increase in life expectancy resulted in a considerable increase in diseases associated with hormonal changes, including osteoporosis, warranting the focus on studies to clarify these interactions.
The present study aims to evaluate the influence of hormonal serum levels of vitamin D, calcitonin, testosterone, estradiol, and parathyroid hormone in patients with fractures attributed to osteoporosis in comparison with young patients with fractures resulting from high-impact accidents.
Materials and Methods
The present project was approved by the Ethics Committee under protocol number 51827515.4.0000.5145.
Study Group
Blood samples were collected from 30 elderly patients with fractures attributed to osteoporosis (T-score ≤ -2.5) (osteoporotic group), and from 30 young patients with fractures resulting from high-impact accidents (control group). Patients with other bone conditions, nonosteoporotic fractures, immunosuppression, malignant neoplasms, or liver disorders were excluded from the study, along with those who did not agree to participate in it. Serum collected from these patients was used for hormone measurement.
Blood Collection
Venous blood collection was always performed in the morning, 1 day after the bone reconstruction surgery indicated by the orthopedist. A blood sample was obtained by venipuncture, using three vacuum collection tubes containing a clot activator and separating gel. Thirty minutes after collection, the samples were centrifuged at 5,000 rotations per minute (rpm) for 10 minutes to obtain serum.
Hormonal Analysis
Serum obtained after blood samples centrifuging was sent for hormonal analysis. Measurement of 1,25-hydroxyvitamin D (Kit Diasorin, Saluggia, Italy), calcitonin (Kit Siemens, Tarrytown, NY, USA), testosterone, estradiol, and parathyroid hormone (Kit Beckman Couter, Indianapolis, IN, United States) was performed using a chemiluminescence technique, a chemical reaction that generates luminous energy. Chemiluminescence reagents are transformed into electrically excited intermediate states and release the absorbed energy as light when becoming less excited.
Statistical Analysis
Data were inserted into a Microsoft Excel (Microsoft Corp., Redmond, WA, USA) spreadsheet and analyzed using Statview statistical software. Results showing non-normal distribution were analyzed with nonparametric methods. The Mann-Whitney test was applied for group comparison, and a Spearman test correlated hormonal levels. Statistical significance was set at p < 0.05.
Results
The present study measured hormones in 30 patients with osteoporosis and in 30 control subjects, totaling 60 people.
The mean age of the patients was 58.8 ± 22.61 years old, and all analyzes compared gender and subjects with or without osteoporosis. [Table 1] shows the number of patients and the mean age from each group.
Table 1
|
Mean Age (years old)
|
Number of Patients (n)
|
Minimal Age (years old)
|
Maximal Age (years old)
|
|
Female control subjects
|
39.5
|
08
|
18
|
58
|
|
Male control subjects
|
39.6
|
22
|
19
|
58
|
|
Women with osteoporosis
|
80.05
|
18
|
64
|
98
|
|
Men with osteoporosis
|
74.9
|
12
|
60
|
88
|
|
Total
|
58.8
|
60
|
18
|
98
|
In the control group, serum vitamin D levels were significantly higher in females when compared with males (Mann-Whitney test; p = 0.0169). Comparing both groups (osteoporosis and control subjects), serum vitamin D levels were significantly higher in women from the control group than in women with osteoporosis (p = 0.0275). There was no significant difference between males and females from the osteoporosis group ([Figure 1A]).
Fig. 1 Hormonal measurement using chemiluminescence in female and male patients diagnosed with osteoporosis and control subjects. (A) Vitamin D, *p = 0.0169 and **p = 0.0275; (B) Testosterone, *p = 0.0023 and **p = 0.0046; (C) Estradiol, p = 0.047; (D) Parathyroid hormone, p = 0.0065; (E) Calcitonin (Mann-Whitney test).
Significantly higher free testosterone levels were observed in males when compared with females in both the control and osteoporotic groups (Mann-Whitney test; *p = 0.0023 and **p = 0.0046). There was no significant difference in free testosterone levels between males from the control and osteoporotic groups ([Figure 1B]).
Estradiol levels were significantly lower in women with osteoporosis compared with those of the control group (Mann-Whitney test; p = 0.047). There was no significant difference in estradiol levels between men and women from the control group and the osteoporotic group ([Figure 1C]).
Parathyroid hormone levels were significantly higher in men with osteoporosis when compared with the control group (Mann-Whitney test; p = 0.0065). There was no significant difference between women from the control group and women with osteoporosis. No significant difference was observed in parathyroid hormone levels when comparing males and females with or without osteoporosis ([Figure 1D]).
There was no significant difference in calcitonin levels between the control and osteoporotic groups, regardless of gender. In addition, there was no significant difference when comparing men and women from both groups ([Figure 1E]).
Discussion
Osteoporosis results from an imbalance of bone remodeling potentially caused by hormonal factors. In addition, more recent studies show that immunological factors also play a role in the pathophysiology of the disease. The present study evaluated hormonal levels in patients with osteoporosis and compared gender-related differences.
Our study revealed significant differences in vitamin D, estradiol, and parathyroid hormone levels. Osteoporotic women and young men had significantly lower levels of vitamin D compared with young women. Studies show that vitamin D deficiency is associated with muscle weakness, bone loss, falls and fractures.[13] In line with the literature, our data suggest that a decrease in vitamin D in older women may contribute to osteoporosis. The present study also showed that reduced estradiol levels are related to the onset of osteoporosis in women > 60 years old, which is consistent with other works, showing that bone health is inversely related to lower estradiol concentrations.[7]
[8]
[14] Estradiol deficiency was also linked to osteoporosis in men > 64 years old,[15] although this association was not observed here.
Bone remodeling is also stimulated by parathyroid hormone. A study with elderly women showed a significant increase in parathyroid hormone levels in women with osteoporosis.[16] In the present study, significantly higher levels of parathyroid hormone were found in men with osteoporosis, showing that it contributes to the onset of the disease in men > 60 years old; in contrast, women present no differences in parathyroid hormone levels.
Testosterone was not a limiting factor for the onset of osteoporosis in our patients. This hormone seems to be more related to differences between males and females. However, a study showed that testosterone deficiency in men > 64 years old is associated with rapid bone loss, leading to osteoporosis.[15] Even though the literature showed that calcitonin acts by inhibiting bone resorption,[17] we found no significant differences in calcitonin levels between groups and genders.
Conclusion
The present study suggests that women with osteoporosis had significantly lower levels of estradiol and vitamin D compared with young women without the disease, whereas men with osteoporosis had significantly higher levels of parathyroid hormone compared with men without the disease. These findings show the importance of hormones and vitamin D in the development of osteoporosis. Although lower testosterone levels are associated with osteoporosis, our study does not show its impact on the disease, except for a significant gender-related difference, regardless of age and of the presence of osteoporosis.
