Parathyroid gland secrete two main hormones, parathyroid hormone and calcitonin. These hormones are instrumental to the system that allows the body to form bone, facilitate vitamin D, which acts like a hormone to the body, and process calcium and phosphate. Calcium and phosphorus metabolism are not directly related to hormones. However, there are also hormonal issues related to these substances that will be discussed below.
The skeleton is made up of many components, one of the most essential of which is calcium. Calcium functions in many different ways and works in areas such as muscle contraction, enzyme activity, blood clotting and hormone release along with many others. In order for health to remain at a high, it is essential that calcium be controlled. Vitamin D, calcitonin, and parathyroid hormone all work together to keep the body’s calcium levels steady throughout intake and excretion. Other hormones may also play a factor in balancing calcium levels.
The parathyroid glands are responsible for creating and storing parathyroid hormone. These glands are located on either side of the neck. The body employes a feedback mechanism that regulates the creation of parathyroid hormone, and that feedback system involves blood calcium levels. Parathyroid hormone functions primarily to control calcium levels by influencing the movement of calcium in and out of the bone, aiding the absorption of calcium from the digestive tract, and helping the kidneys to retain calcium.
The second major hormone involved in calcium regulation and metabolism is vitamin D. This hormone is formed in the skin after it is exposed to ultraviolet light, such as sunlight, and is present in many species, including horses and people. Dogs, on the other hand, are not able to form enough of this hormone on their own and are dependent upon dietary intake to supply it. Parathyroid hormone, conditions that stimulate parathyroid hormone, and reduced phosphate levels all increase the formation of vitamin D.
Calcitonin is another hormone and it is secreted by specific cells of the thyroid gland in all mammals. This hormone is released to prevent hypercalcemia, or abnormally high levels of calcium, when levels of blood calcium increase.
Hypercalcemia In Dogs
Hypercalcemia is a condition that exists when there are abnormally high levels of calcium in the blood. Symptoms of hypercalcemia depend on the duration, rate of escalation, and level of calcium in the blood. Most commonly dogs with hypercalcemia will present with symptoms including seizures, muscle twitching, vomiting, reduced appetite, weakness, constipation, depression, and, the most common symptom, increased urination and thirst.
Hypercalcemia in dogs is most often linked to tumors, kidney disease, or an underactive adrenal gland – Addison’s disease. However, there are less common causes, as well, such as a vitamin D overdose, an overactive parathyroid gland, and granulomatous disease.
Treatment of hypercalcemia changes depending on the underlying condition that is causing the illness. The flip side of that, however, is that the cause is not always readily apparent. More often than not supportive treatment is necessary in order to lower the level of calcium in the blood. Supportive treatments can include glucocorticoids, sodium bicarbonate, diuretics, sometimes called water pills, and an increase in fluids.