From the Guidelines
Yes, calcitonin lowers blood calcium levels, while parathyroid hormone (PTH) increases blood calcium levels by releasing calcium from bones. These two hormones work antagonistically to maintain calcium homeostasis in the body. Calcitonin, produced by C cells in the thyroid gland, responds to high blood calcium levels by inhibiting osteoclast activity in bones, reducing bone resorption, and increasing calcium excretion through the kidneys 1. This effectively decreases calcium concentration in the bloodstream. Conversely, PTH, secreted by the parathyroid glands in response to low blood calcium, stimulates osteoclasts to break down bone tissue and release calcium into the blood. PTH also enhances calcium reabsorption in the kidneys and increases vitamin D activation, which promotes intestinal calcium absorption.
The regulation of calcium levels is crucial for various physiological processes, including nerve function, muscle contraction, and blood clotting. The dual-hormone system of calcitonin and PTH provides precise regulation of calcium levels. According to a study published in the American Journal of Kidney Diseases, parathyroid hormone stimulates bone resorption and kidney distal tubular calcium reabsorption, increasing serum calcium levels 1. On the other hand, calcitonin has been shown to inhibit osteoclast activity, reducing bone resorption and increasing calcium excretion through the kidneys 1.
Key points to consider:
- Calcitonin lowers blood calcium levels by inhibiting osteoclast activity and increasing calcium excretion through the kidneys.
- PTH increases blood calcium levels by stimulating osteoclasts to break down bone tissue and release calcium into the blood.
- The dual-hormone system of calcitonin and PTH provides precise regulation of calcium levels, which is crucial for various physiological processes.
- Abnormalities in calcium regulation can lead to various health issues, including bone diseases and disorders. It is essential to note that the most recent and highest quality study on this topic is from 2019, which discusses the clinical practice recommendations for the diagnosis and management of X-linked hypophosphataemia 1. However, the specific details about calcitonin and PTH are more accurately described in the 2003 study published in the American Journal of Kidney Diseases 1.
From the FDA Drug Label
In four open-label clinical trials enrolling 53 patients, calcitonin-salmon has been shown to lower elevated serum calcium levels of patients with carcinoma (with or without metastases), multiple myeloma, and primary hyperparathyroidism (lesser response) With patients’ pre-therapy serum calcium levels as controls, reduction in serum calcium was evident within 1 to 2 hours of administration The peak effect occurred within 24 to 48 hours of injection and administration of calcitonin-salmon every 12 hours maintained a hypocalcemic effect for approximately 5 to 8 days, the time period evaluated for most patients in the clinical trials.
Calcitonin lowers blood calcium levels. Parathyroid hormone (PTH) is not directly addressed in the provided text in the context of the question, but it is known to increase blood calcium levels by releasing calcium from bones. However, this information is not present in the provided drug label. The provided text only discusses the effect of calcitonin on blood calcium levels, but does not compare it directly to parathyroid hormone in this context 2.
From the Research
Calcium Regulation
- Calcitonin is a hormone that helps to lower blood calcium levels by inhibiting osteoclast activity, which are the cells responsible for breaking down bone tissue and releasing calcium into the blood 3.
- Parathyroid hormone (PTH), on the other hand, is a hypercalcemic hormone that acts to increase blood calcium levels by promoting calcium release from the bone, renal calcium reabsorption, and phosphate excretion 4.
Mechanisms of Action
- PTH stimulates the release of calcium from the bone by activating osteoclasts, which break down bone tissue and release calcium into the blood 4.
- Calcitonin, in contrast, inhibits osteoclast activity, thereby reducing the amount of calcium released from the bone into the blood 3.
- Both hormones play a crucial role in maintaining calcium homeostasis in the body, with PTH acting to increase blood calcium levels and calcitonin acting to decrease them 5, 6.
Hypercalcemia and Hypocalcemia
- Hypercalcemia, or elevated blood calcium levels, can be caused by a variety of factors, including primary hyperparathyroidism, malignancies, and certain medications 5, 6.
- Hypocalcemia, or low blood calcium levels, can be caused by a variety of factors, including vitamin D deficiency, kidney disease, and certain medications 7.
- Understanding the mechanisms of action of PTH and calcitonin is essential for diagnosing and treating disorders of calcium homeostasis, such as hypercalcemia and hypocalcemia 4, 3.