Parathyroid Cancer – Tissue and Symptoms

This article describes the basic anatomy and functions of the parathyroid glands.  By having a basic understanding of what the parathyroid glands are, the symptoms of parathyroid cancer will be better understood.

The parathyroid glands are small oval shaped glands that are found in the neck near the thyroid gland.  The thyroid gland is a shield like structure that sits in front of the windpipe.  At each corner of this shield, there is usually a parathyroid gland.  Most people have four parathyroids but it is possible to have less or more.  They usually are found near the thyroid gland but they can form in other places in the neck or even in the chest.  The parathyroid glands are very small and average about 30 grams and a centimeter or less in size.  The parathyroid glands share a common blood supply with the thyroid gland.

Although small, the parathyroid glands play an extremely important role in metabolism, electrolyte regulation, bone and kidney function.  The main role of the parathyroid glands is to regulate bodily calcium.  The parathyroid glands make a hormone that was ingeniously termed parathyroid hormone.  Parathyroid hormone is sometimes abbreviated as PTH.  Parathyroid hormone has actions on the intestines, bones and kidneys to regulate calcium in the body.

Calcium plays many key roles in the body.  Small amounts of calcium are found in the blood.  Some is free and dissolved in the blood and most of the calcium in the blood is bound to transport proteins.  Calcium is a key component of bone.  Calcium is one of the electrolytes that help muscle contraction.  Muscles contract with the movement of ions that forms an electrical signal causing muscle proteins to shorten and thus muscle contracts.  Calcium also plays a key role in transmission of nerve signals.  Calcium is also a signal that occurs in cells to assist the action of many hormones.

Considering the vast influence of parathyroid glands, it is easy to understand how disease of the parathyroid glands can affect the entire body.  Before parathyroids were discovered, some doctors tried to remove tumors of the adjacent thyroid gland and unknowingly removed the parathyroids as well.  Without these essential glands death from severe calcium disorder is possible.

The parathyroid glands have sensors that detect the level of calcium in the blood like a thermostat regulates the function of a heating unit.  When the temperature drops, the thermostat turns the heating unit on and when the temperature meets its goal the unit is turned off.  There are many similar feedback loops in the body and the parathyroid gland functions on a similar feedback loop.  When the calcium level gets too high, the parathyroid glands will decrease the production of parathyroid hormone until the level falls back into the normal range.  If this sensing mechanism breaks, the calcium level could either drop dangerously or rise to fatal levels depending on the type of dysfunction with the sensing mechanism.

The most common cause of very high blood calcium levels is a parathyroid gland that produces hormone (PTH) without feedback regulation.   The parathyroid hormone regulates calcium by 1) controlling absorption of calcium from the intestine, 2) regulating calcium in the bone and 3) regulating calcium clearance by the kidney.  When calcium is low, PTH will be secreted in higher amounts.  The parathyroid hormone will cause the kidneys to retain calcium as the blood is filtered through.  The bones will also undergo some breakdown by osteoclasts under the direction of parathyroid hormone.  The intestine (the small intestine mostly) is directed to absorb calcium from the diet in larger amounts when PTH levels are higher.  All of these mechanisms act in concert to rapidly adjust the calcium levels.

A famous jingle that most medical students learn to remember the problems that can occur with poor calcium regulation is “stones, bones, groans and moans.”  When calcium levels are high this can cause kidney stones, painful bones, abdominal pain, and changes in the mood.  Overall, overactive parathyroid glands are more common than underactive glands.  Having too little parathyroid function is most commonly related to some type of treatment for the adjacent thyroid gland that either injured them or removed them entirely.  There are four parathyroid glands in most people but one good functioning gland is adequate to maintain normal calcium levels.  This is why one of the treatments for overactive parathyroid glands is to remove either the most active gland or 80-90% of the entire lot.

Low calcium levels are mainly noticed due to their effects on muscles.  Tingling and spontaneous spastic like contractions of muscles can occur with low calcium levels.  Very high calcium levels can cause confusion and fatal heart rhythm disturbances.

Parathyroid cancer generally causes severe over-production of parathyroid hormone.  This usually causes the symptoms to be recognized early in the course of the disease.  The massive elevation in calcium can be fatal if not treated.

REFERENCES:

  1. Townsend Jr, CM; Beauchamp RD; Evers BM; Mattox KL. (2008) Townsend: Sabiston Textbook of Surgery, 18th ed.  Chapter 37.  New York, NY: Saunders.
  2. www.cancer.gov/cancertopics/types/parathyroid
  3. Cameron JL; Cameron AM.  (2010) Cameron: Current Surgical Therapy, 10th ed. Chapter 610. Philadelphia, PA: Elsevier Saunders
    1. Incidence and prognosis of parathyroid gland carcinoma: A population-based study in The Netherlands estimating the preoperative diagnosis.Schaapveld M, Jorna FH, Aben KK, Haak HR, Plukker JT, Links TP.Am J Surg. 2011 Aug 20. PMID: 21861982
    2. This article was originally published on September 3, 2012 and last revision and update was 9/4/2015.