Generally speaking, there is a physiological decline in renal function in the elderly, which is characterized by a decrease in the production of 1, 25-(OH2) D3 and a decrease in blood calcium, thus stimulating the secretion of parathyroid hormone. Therefore, most scholars report that the concentration of parathyroid hormone in blood often increases with age, and the increase range can reach 30% or even higher. The research results of parathyroid function in postmenopausal women with osteoporosis show that both normal and hyperfunction are generally considered as the elderly.
The research shows that the blood calcitonin level of women in all age groups is lower than that of men, and the blood calcitonin level of menopausal women is lower than that of menopausal women. Therefore, it is considered that the decrease of serum calcitonin level may be one of the reasons why women are prone to osteoporosis. According to the endocrinology department of Peking Union Medical College Hospital, the increase of serum calcitonin in women after intravenous calcium supplementation was significantly lower than that in men, and the basic value and increase of serum calcitonin were negatively correlated with age. After intravenous infusion of calcitonin in healthy volunteers before and after menopause, there is no significant difference in calcitonin reserve function, but the decrease in bone mass and calcitonin reserve function in osteoporosis patients is more obvious, suggesting that the decrease in calcitonin reserve function may be involved in the occurrence of osteoporosis. Most reports about the decrease of serum calcitonin level in postmenopausal women with osteoporosis, but there are also reports of normal and slight increase.
The activity of 1-α- hydroxylase in the kidney of osteoblast function is impaired with age, and the related concentration of 1, 25-(OH2) D3 is decreased, which is also involved in the formation of osteoporosis and other endocrine disorders, such as Cushing's syndrome, which produces too many endogenous corticosteroids or chronic thyrotoxicosis, leading to increased bone absorption or excretion, which are related to osteoporosis.
2. Genetic factors Osteoporosis is common in whites, especially in northern Europe, followed by Asians, but rare in blacks.
Bone mineral density is an important index to diagnose osteoporosis. BMD value is mainly determined by genetic factors, followed by environmental factors. It is reported that the BMD difference between young twins is four times that between identical twins, while that between adult twins is 19 times that of identical twins. Bone mineral density is closely related to the polymorphism of vitamin D receptor genotype. Morrison et al reported that the genotype of vitamin D receptor can predict the difference of bone mineral density, accounting for 75% of the whole genetic influence. After adjusting various environmental factors, the bone mineral density of bb genotype can be about 15% higher than that of BB genotype. In the incidence of spinal fracture, bb genotype is about 10 years later than bb genotype, while in the incidence of hip fracture, BB genotype walker is only 1/4 of BB genotype. The preliminary results of this study show that there are great differences between races and countries, and the final results still need further study. Other studies on the relationship between collagen gene and estrogen receptor gene and osteoporosis have also been reported, but there is no clear conclusion yet.
3. The study of nutritional factors found that the intake of calcium in adolescence is directly related to the bone mass in adulthood, and the lack of calcium leads to the increase of PTH secretion and bone absorption. People who eat a low-calcium diet are prone to osteoporosis, and vitamin D deficiency leads to bone matrix mineralization damage, which can lead to osteomalacia and backward new bone formation. If calcium is deficient at the same time, vitamin C is essential for the synthesis of hydroxyproline in bone matrix, which can maintain the normal growth of bone matrix and maintain sufficient alkaline phosphatase production by bone cells. If vitamin c is lacking, it can be used.
4. disuse factor: muscle exerts mechanical force on bone tissue. Musculoskeletal strength and high bone density.
Due to the decrease of activity, muscle strength, mechanical stimulation and bone mass of the elderly are weakened. At the same time, the weakening of muscle strength and coordination disorders make the elderly more likely to fall, and when accompanied by decreased bone mass, fractures are prone to occur. Old people who have been bedridden for a long time after suffering from stroke and other diseases are prone to osteoporosis due to bone loss caused by disuse factors.
5. Drugs and disease anticonvulsants, such as phenytoin sodium, phenobarbital and carbamazepine, can lead to treatment-related vitamin D deficiency and intestinal calcium absorption disorder, as well as secondary hyperparathyroidism. Excessive use of antacids, including aluminum preparations, will inhibit the absorption of phosphate and lead to the decomposition of bone minerals. Glucocorticoid can directly inhibit bone formation, reduce intestinal calcium absorption, increase renal calcium excretion, secondary parathyroid dysfunction, and the production of sex hormones.
Cytokines produced by tumor cells, especially multiple myeloma, can activate osteoclasts and leukemia and lymphoma in children or adolescents. Osteoporosis in the latter is usually a localized gastrointestinal disease, such as inflammatory bowel disease that leads to malabsorption and eating disorders. Anorexia nervosa leads to rapid weight loss and malnutrition, which is related to amenorrhea. Hemoglobin anemia is caused by excessive proliferation of bone marrow and thinning of trabecular junction, and such patients may have secondary hypogonadism.
6. Other factors Alcoholism has a direct toxic effect on bones. Smoking will increase the metabolism of estrogen in the liver and have a direct impact on bones. In addition, it can also lead to weight loss and lead to early menopause. Long-term strenuous exercise can lead to idiopathic osteoporosis.