PARATHYROID GLAND ::
There are four parathyroid glands which are normally found on the posterior surface of the thyroid gland Each gland consists of a closely packed mass of two types of cells One of these types of cells secrete the hormone parathormone
Parathormone is a polypeptide hormone concerned with control of calcium ion concentration in the blood It is secreted in response to a fall in calcium ion concentration and it tends to raise it
Parathormone Produces its effect by ::
1.Mobilisation of calcium ions from the bones by stimulating the bone cells
2.Prevention of loss of calcium ions in the urine by promoting reabsorption of calcium ions from the tubules back into the blood
3. Increasing the absorption of calcium from the gut It is however much less important than vitamin D in this respect Parathyroid hormone (parathormone) calcitonin and vit D are the chief hormones regulating the calcium ion concentration of blood calcitonin and Vit D work synergistically to increase the deposition of calcium in the bone and decrease the calcium level in blood Parathormone has opposite or antagonistic effect to calcitonin and Vit D It produces increase in calcium level in blood by mobilizing calcium from the bones
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