There are two pairs of small parathyroid glands located on the posterior surface of the thyroid gland, each weighing around 40 mg. The glands contain chief cells that secrete parathyroid hormone (PTH). PTH functions to increase blood calcium, magnesium, and phosphate levels by stimulating bone resorption and renal calcium reabsorption and calcitriol production. The levels of PTH and calcitonin are regulated inversely in response to calcium levels in the blood to maintain normal calcium homeostasis.

1. PARATHYROID GLAND
Ms.Anu Sebastian: B.Pharm; M.Pharm
Assistant Professor,
Dept. Of Pharmacology
Nirmala College Of Pharmacy
Muvattupuzha,Ernakulam,Kerala

3.  Two pairs of parathyroid glands are present in the body
,each pair on the posterior surface of the lateral lobes of
thyroid gland.
 On each lobe of thyroid gland , on the posterior surface; a
pair of parathyroid glands are present. i.e one superiorly
and other inferiorly.
 Parathyroid glands are small, round masses of tissues with
a weight of 40 mg.

4.  The parathyroid gland contains two types of epithelial
cells:
 Chief /principal cells: which secretes
Parathormone/Parathyroid hormone
Oxyphil cells: Function is not known

5. FUNCTIONS OF PARATHYROID HORMONE
 Increases blood calcium, magnesium & phosphate ions : by
increasing the number & activity of osteoclasts.
 Increases the rate of loss of phosphate ions from blood to urine
& slows the rate of loss of magnesium & calcium into
urine.thereby increases bloos ca & mg & decreases phosphate.
 This hormone stimulate kidney to increas the rate of formation
of calcitriol(active form of Vit.D)

6. REGULATION OF PARATHYROID HORMONE & CALCITONIN
Increase blood calcium level than normal
stimulate
Thyroid gland to release calcitonin
Calcitonin inhibits action of osteoclasts
Inhibits bone resorption /destruction
Decrease calcium release
Decrease blood calcium level

7. Decrease blood calcium level than normal
stimulate
Parathyroid gland to release Parathormone
Parathormone stimulate osteoclasts
bone resorption /destruction
Increase release of calcium into blood
Increase blood calcium level

8. THANK YOU