Calcitonin

| Home | | Pharmacology |

Chapter: Essential pharmacology : Drugs Affecting Calcium Balance

Calcitonin is the hypocalcaemic hormone discovered by Copp in 1962. It is a 32 amino acid single chain polypeptide (MW 3600) produced by parafollicular ‘C’ cells of thyroid. Parathyroids, thymus and cells of medullary carcinoma of thyroid also contain calcitonin.


CALCITONIN

 

Calcitonin is the hypocalcaemic hormone discovered by Copp in 1962. It is a 32 amino acid single chain polypeptide (MW 3600) produced by parafollicular ‘C’ cells of thyroid. Parathyroids, thymus and cells of medullary carcinoma of thyroid also contain calcitonin.

 

Synthesis and secretion of calcitonin is regulated by plasma Ca2+ concentration itself: rise in plasma Ca2+ increases, while fall in plasma Ca2+ decreases calcitonin release. However, the physiological role of calcitonin in regulating plasma Ca2+ appears to be minor. The plasma t½ of calcitonin is 10 min, but its action lasts for several hours.

 

Actions

 

The actions of calcitonin are generally opposite to that of PTH. It inhibits bone resorption by direct action on osteoclasts—decreasing their ruffled surface which forms contact with the resorptive pit. Whether it also promotes calcium deposition by osteoblasts is not certain. The hypocalcaemic action of calcitonin lasts ~8 hours.

 

Calcitonin inhibits proximal tubular calcium and phosphate reabsorption by direct action on kidney. However, hypocalcaemia overrides the direct action by decreasing the total calcium filtered at the glomerulus—urinary Ca2+ is actually reduced.

 

The actions of calcitonin are mediated through a Gprotein coupled receptor and increase in cAMP formation, but its target cells are different from that of PTH.

 

Preparation And Unitage

 

Synthetic salmon calcitonin is used clinically, because it is more potent due to slower metabolism. Human calcitonin has also been produced. 1 IU = 4 μg of standard preparation.

 

CALSYNAR, ZYCALCIT: Synthetic salmon calcitonin 100 IU/ml amp. for i.m. or s.c. injection.

Adverse effects experienced are nausea, flushing, tingling of fingers, bad taste and allergic reaction. By lowering plasma Ca2+ calcitonin may interfere with the action of digoxin.

 

Uses

 

1. Hypercalcaemic states Hyperparathyroidism, hypervitaminosis D, osteolytic bony metastasis and hypercalcaemia of malignancy; 4–8 IU/kg i.m. 6–12 hourly only for 2 days. It acts rapidly within 4 hours, the response peaks at 48 hours and then refractoriness develops. Calcitonin is a relatively weak hypocalcaemic drug. Therefore, used only to supplement BPNs initially, because they take 24–48 hours to act.

 

2. Postmenopausal osteoporosis: 100 IU s.c. or i.m. daily along with calcium and vit D supplements.

 

A nasal spray formulation delivering 200 IU per actuation has become available (MIACALCIN NASAL SPRAY 2200 IU in 2 ml). One spray in one nostril daily has been shown to increase bone mineral density in menopausal women. It is less effective than HRT/BPNs. Calcitonin is indicated only when other drugs cannot be given and in women who are menopausal for at least 5 years with definite evidence of osteoporosis. Rhinitis, epistaxis, nasal ulceration and headache are the side effects.

 

3. Paget’s disease 100 U daily or on alternate days produces improvement for few months. Later, resistance usually develops due to production of antibodies. Bisphosphonates are preferred; calcitonin may be used as adjuvant or 2nd line drug.

 

Contact Us, Privacy Policy, Terms and Compliant, DMCA Policy and Compliant

TH 2019 - 2022 pharmacy180.com; Developed by Therithal info.