1. The Parathyroid Gland By Jonah Carleton, & Elise Voorhis

2. Overview Thyroid Gland Parathyroid Gland Location
Four rice grain sized glands located on/behind the thyroid gland
Located in the center of the neck, at the back
Behind the thyroid gland
Top two are superior and bottom two are inferior
Hormones Released
Parathyroid Hormone (PTH)
Function
Stabilizes calcium and phosphorus levels
PTH raises the level of calcium in the blood
Breaks down bone, causing the release of calcium
Not good for bones, but beneficial for other cells
Makes it easier for body to absorb calcium from food
Limits kidneys from excreting too much calcium
Calcium not lost in urine
Begins to produce calcitriol
PTH decreases the level of phosphorus in the blood
Calcitriol
Helps the body absorb as much calcium as possible
Regulated by Calcium Sensing Receptor (CaSR)
The CaSR senses changes in blood calcium levels and releases PTH accordingly
Thyroid Gland
Parathyroid Gland

3. The Parathyroid Gland Operates in a Negative Feedback Loop
Feedback loop for calcitonin and parathyroid hormone
Calcitonin decreases blood calcium levels when they become too high
Calcitonin is produced in the thyroid gland, but it is involved in a loop with PTH
Parathyroid releases PTH when the blood calcium levels are too low
Signaled by the Calcium Sensing Receptor (CaSR)
Causes levels of calcium to increase
Calcium taken out of the bones
Increased PTH activates the vitamin D system (calcitriol system)
Calcitriol is “active vitamin D”
Vitamin D is converted into calcediol in the liver
This calcediol is then turned into calcitriol in the kidneys
This final transformation is regulated by PTH
Parathyroid stops releasing PTH when the blood calcium levels are normal or too high
Calcium signals to CaSR which conveys message to the Parathyroid

4. Hyperthyroidism
Disease where a parathyroid is overactive and produces too much PTH
Causes unusually high levels of calcium in the blood
Due to overactive parathyroid
Primary and Secondary forms
Both usually cannot be prevented
Vitamin D deficiency can lead to secondary hyperparathyroidism
Too much calcium gets taken out of bones
Weakens bones
Can be either 1, 2, 3, or all 4 of the glands being hyperactive
Very uncommon for 3 or 4 to by hyperactive (15-10%)
Is more common as people get older
Women are twice as likely to develop hyperparathyroidism as men
Can be caused by overexposure of radiation
Most cases sporadic
5% are inherited
Is treated by surgery
Enlargement of parathyroid gland called adenoma

5. Citations
Campbell, Neil A., et al. Campbell Biology in Focus. Pearson Education Limited, 2017.
“Parathyroid Glands: Function.” Function of the Parathyroid Glands, endocrinediseases.org/parathyroid/parathyroid_background.shtml.
“Parathyroid Disorders.” Medlineplus, U.S. National Library of Medicine, medlineplus.gov/parathyroiddisorders.html.
Kleerekoper, Michael. “About the Parathyroid Glands.” Empoweryourhealth, conditions/parathyroid.
“Parathyroid Gland Introduction.” Parathyroid.com and Hyperparathyroidism,
Parathroid Gland -
Enlarged Gland -
Feedback Loop-