Question

A 55-year-old woman went to the doctor with complaints of muscle weakness, fatigue, night cramps, and pain in the lumbar region. Radioscopy showed a decrease in bone density, a violation of the structure of bones. The patient was diagnosed with osteoporosis (porous bones). Osteoporosis is a common cause of bone fractures. The doctor prescribed treatment with calcitriol and calcium preparations. Calcitriol receptors exist in two allelic variants - B and b. Studies have shown that dominant BB homozygotes are more prone to smallpox, and this patient has only such a genotype. What are other causes of osteoporosis and what is the mechanism of the therapeutic effect of calcitriol? For an answer
1. Indicate the target organs of calcitriol and the mechanism of action on target cells;
2. Write a scheme for the synthesis of calcitriol;
3. What are the main causes of osteoporosis;
4. Explain why the use of calcitriol and calcium preparations improves the condition of patients with osteoporosis.

Answer 1

1.Calcitriol and parathyroid hormone regulate the levels of circulating calcium and phosphate by the action on target organs which include (bones, intestine and kidney.

2.Aging, alcohol intake, prevalence of breast cancer, corticosteroid treatment, anorexia nervosa, bulimia, hyperthyroidism, hypopituitarism, rheumatoid arthritis and menopause are some causes of osteoarthritis.

3. Biosynthesis of calcitriol

4. Use of calcium and calcitriol increase the calcium uptake from bones via calcium absorption by intestinal absorption. There is prevention of bone loss