AGENTS FOR BONE AND BONE GROWTH : CALCIUM PREPARATIONS

 99% of body calcium is found in the bones as hydroxyapatite.  The remaining calcium is found in the extracellular fluid compartments and is involved in blood clotting mechanism, muscle contraction and nerve function.  Sources of calcium: Milk, milk products, egg, meats, green vegetables, potato, rice.

In plasma calcium remains in three forms:  Ionized calcium : 50%, this is physiologically active and diffusible  Protein bound calcium :41%, in combination with plasma protein  Calcium complexed to anions : 9%, is diffusible but is combined with citrate and phosphate

 Calcium is absorbed from the upper part of the small intestine where the intestinal contents are still acidic.  There it exists as ionized water soluble salts.  As the intestinal contents become neutral to alkaline, calcium is precipitated as dibasic phosphate, carbonate, oxalate, sulfate salts and insoluble calcium soaps.

 Parathyroid hormone and Vitamin D metabolite controls calcium absorption.  Cholecalciferol (Vitamin D3) is hydroxylated at the C-25 position in the liver and at the C-1 position in the kidneys to form 1,25-dihyroxy cholecalciferol.  This causes synthesis of calcium-binding protein that transfers the calcium cation across the intestinal wall.

 1. Parathyroid hormone increases blood Ca²⁺ levels by 3 ways - Resorption of Ca²⁺ from bone : this hormone removes calcium salts from bone and decreases deposition of calcium salt on bone. - Decreases excretion of Ca²⁺ from kidney - Increase absorption of Ca²⁺ from intestine

 2. Calcitonin (hormone secreted by thyroid gland) decreases blood Ca²⁺ levels (by inhibiting bone resorption).  3. in Phosphate levels Ca²⁺ level : Parathyroid hormone inhibits renal tubular reabsorption of phosphorus, thus increasing excretion of phosphorus and Ca²⁺ level.

Causes :  Hyperparathyroidism  Hypervitaminosis D  Bone neoplastic (tumour) diseases Symptoms:  Fatigue  Muscle weakness  Constipation  Anorexia (loss of appetite)  Cardiac irregularities

Causes :  Hypoparathyroidism  Vitamin D deficiency  Osteoblastic metastasis (spreading bone cancer)  Steatorrhea (fatty stool)  Acute pancreatitis  Acute hyperphosphatemia This condition can lead to  Hypocalcemic tetany : decrease in extracellular Ca²⁺ affects the nerve and muscle cells causing excessive spasm of skeletal muscle cells and laryngospasm.  disorders in bone metabolism

 Bone is a dynamic tissue involving constant exchange of calcium and phosphorus ions with the body fluids.  Bone is a storage tissue for calcium ions. Bone disorders:  Osteoporosis : Loss of bone thickness  Osteopenia : mild thinning of bones  Osteonecrosis : death of bone tissue caused by a poor blood supply to the bones (due to autoimmune disorders and steriod use).  Paget’s disease

 Osteoporosis : Reduced volume of bone tissue per unit volume of anatomical bone/ Loss of bone thickness.  Bones become weak. Causes: 1. Decreased calcium absorption due to diet or problem with intestinal absorption 2. Vitamin D deficiency or inability to hydroxylate Vitamin D 3. Increased sensitivity to Parathyroid hormone, particularly in postmenopausal women ( too much PTH causes the bone to release calcium constantly into the blood and so bone loses its density). 4. Decreased physical activity 5. Hormonal changes – lack of estrogen 6. Kidney disease

 Increased calcium and Vitamin D intake  Increased phosphate such as sodium monohydrogen phosphate intake  Administration of sodium fluoride  Administration of calcitonin Paget’s disease: a disease characterized by decalcification and bone softening initially followed by calcium deposition with resultant thickening and deformity. Treatment: phosphate salts / calcitonin

Supplements  Calcium supplements are available without a prescription, but not all calcium supplements are equal. Think about the following when choosing your supplement: Purity  When picking a calcium supplement, look on the label for “purified” or the BP/USP symbol. Dose  When buying calcium supplements, check the label for the elemental calcium content, not the total content. Elemental calcium is the amount of calcium your body actually can use. For example, a tablet containing 500 mg of calcium carbonate provides 200 mg of elemental calcium. Therefore, one tablet provides only 200 mg of calcium, not 500 mg.

 Calcium supplements are available alone or combined with other vitamins, such as vitamin D. Since vitamin D must be changed before it becomes active, you do NOT need to take vitamin D with your calcium in order to absorb the calcium.  Calcium carbonate (Tums or Caltrate) is the most common type of calcium tablets and the least expensive on the market. Calcium carbonate requires extra stomach acid for best absorption, so it should be taken with meals.

 Calcium citrate (Citracal or Solgar): Calcium citrate does not require extra stomach acid for absorption, so you can take it anytime, even on an empty stomach. Calcium citrate, however, usually provides less elemental calcium per pill, so you may need to take more tablets per day depending on your needs. Calcium citrate is also more expensive than some other types of calcium supplements.  Calcium gluconate and calcium lactate :have a low amount of elemental calcium

 Dolomite, bone meal or oyster shell :At this time, these calcium supplements are not tested by any regulatory agency for lead content or other heavy metals. They do not have any advantages over other types of calcium supplements.  Coral calcium :coral calcium is just calcium carbonate and offers no advantage over other brands of calcium carbonate.