Parathyroid hormone regulates blood calcium levels through a negative feedback regulatory pathway. Dysfunction in hormone levels, therefore, produces abnormal calcium levels. The accompanying clinical syndromes range from bone density problems to neurological conditions.
The Importance of Calcium
As the most abundant mineral in your body, calcium plays a critical role in many physiological processes. All muscle types, including cardiac and skeletal, require calcium to perform contractions. The microscopic filaments that convert chemical energy into mechanical motion would not function without plenty of calcium entering the cells. The function of your entire nervous system is similarly dependent on the presence of the correct level of calcium ions, according to the National Institutes of Health. The process of neurotransmitter release, or the secretion of chemical signals between nerve cells, relies on the entry of calcium into these cells. Without proper calcium levels, synaptic vessel fusion and neurotransmitter release become dysfunctional, producing various neurological symptoms.
Parathyroid Hormone and Calcium
Also known as PTH, parathyroid hormone is known as the master regulator of blood calcium and phosphorous levels. Synthesized and released from the parathyroid glands, PTH acts on bone cells to increase calcium release into the circulation. PTH also acts on the kidneys to boost blood calcium by increasing reabsorption from the urinary filtrate. The gut also contains receptors for PTH and will respond to its release by increasing calcium absorption from intestinal contents. Normally, the levels of PTH in the blood are regulated by blood calcium levels. Specifically, PTH concentration increases as blood calcium levels decrease. This creates a well-balanced, negative feedback loop in which PTH levels recognize and respond to changes in calcium. Disease often results following a disruption of this balancing, homeostatic mechanism.
Hyperparathyroidism
When parathyroid hormone is secreted in excess, calcium levels in the blood rise significantly, which can cause a variety of cardiac and neurologic problems. Hyperparathyroidism, or HPT, comes in two forms: primary and secondary. Primary HPT occurs when the parathyroid glands are producing hormone uncontrollably. In these cases, the root defect lies in the gland itself becoming overactive. In secondary HPT, there is a separate cause of low calcium in the body. This situation stimulates the production of PTH in the glands. In this case, the root problem lies in the calcium deficiency, and the PTH glands are responding appropriately. Regardless of the underlying cause, the accompanying symptoms of hyperparathyroidism include osteoporosis, kidney stones, excessive urination, nausea and abdominal pain, according to the Mayo Clinic. Medications are available to treat this condition and should be discussed with your doctor along with other surgical options.
Hypoparathyroidism
The hypo- prefix always indicates low. Hypoparathyroidism is the secretion of an abnormally low amount of PTH. Deficiencies in this hormone result in low blood calcium levels, decreased bone calcium and increased levels of phosphorus. Symptoms of this condition include fatigue, weakness, painful menstruation, anxiety and headaches, says Mayo Clinic. Typically, these conditions are treated with supplements to improve calcium and phosphorous levels on a chronic basis.
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