Calcium (Serum): 8.5 - 10.5 mg/dL (2.12 - 2.57 mmol/L )
Calcium (Ionized) Serum: 4.5 - 5.6 mg/dL (1.1-1.4 mmol/L)
Vitamin D and calcium requirements (RDA)
Body Calcium
99% in bone.
1% in ECF:
[50% in its free ionized form]
[40% complexed with albumin]
[10% complexed with anions such as phosphate.]
Less than 1% of the body's calcium is contained within the ECF, yetthis concentration is regulated carefully by the parathyroid hormoneand calcitonin. Parathyroid hormone is released by theparathyroid gland in response to a low serum calcium level. Itincreases resorption of bone (movement of Ca++ and PO4 out of thebone); activates vitamin D, which increases the absorption of calciumfrom the GIT; and simultaneously stimulates the kidneys to conservecalcium and excrete phosphorus. Calcitonin is produced by thethyroid gland when serum calcium levels are elevated (inhibits boneresorption).
The ECF gains Ca++ from intestinal absorption and resorption from bones. It is lost from the ECF via secretioninto the GIT, urinary excretion, and deposition into bone.
Calcium is present in 3 different forms in the plasma: ionized, boundand complexed. Only the ionized calcium is physiologically important.The percentage of calcium that is ionized is affected by pH,phosphorus, and albumin levels. The relationship betweenionized calcium and plasma pH is reciprocal (increase in pH decreasespercent of Ca++ ionized). Patients with alkalosis for example mayshow signs of hypocalcemia despite a normal total calcium level.Changes in albumin will affect total serum calcium without changingthe level of free calcium. (decreased albumin
decreasedtotal Ca++ constant free Ca++)
Signs and symptoms:Numbness with tingling offingers, extremities and circumoral regionhyperactive reflexes,muscle cramps,carpopedalspasm, stridor,tetany,seizures.Positive Trousseau's sign (carpalspasm with BP cuff) and positive Chvostek's sign (contraction offacial and eyelid muscles when facial nerve tapped). Cardiaceffects include decreased myocardial contractility and heart failure.
History and risk factors:
1) Decreased ionized calcium: alkalosis;administration of large quantities of citrated blood (may bindcalcium); hemodilution (volume replacement etc.)
2) Increased calcium loss in body fluids:certain diuretics.
3)Decreased intestinal absorption:decreased intake; impaired vitamin D metabolism (renal failure);chronic diarrhea, post-gastrectomy.
4) Hypoparathyroidism:congenital or acquired.
5) Hyperphosphatemia:e.g. renal failure. When hypocalcemia persists, it is best to delaycalcium supplementation until the serum phosphate level is below 6mg/dL to reduce the risk of metastatic calcification.
6) Hypomagnesemia(decreased PTH action and release). Chronic alcoholism; acutepancreatitis. Hypocalcemia is difficult to correct withoutfirst normalizing the serum magnesium concentration.
Diagnostic tests:
-Total serum calcium may be less than8.5 mg/dl. Serum calcium levels should be evaluated withserum albumin. For every 1.0 mg/dL drop in serum albumin, thereis a 0.8 - 1.0 mg/dL drop in the total calcium level.
-Ionized calcium will be less than 4.2mg/dL. Symptoms of hypocalcemia usually occur when ionized levelsfall to <2.5 mg/dL.
-Parathyroid hormone: decreased levelsoccur in hypoparathyroidism.
-Magnesium and phosphorus levels:may be checked to indentify potential causes of hypocalcemia.
Treatment should be based on:
(1) Symptoms present: Paresthesias, tetany, carpopedal spasm,seizures
(2) Signs: Chvosek's or Trousseau's signs, impaired cardiaccontractility, prolongation of the QT interval, bradycardia).
(3) Absolute level of calcium
(4) Rate of decrease (e.g. acute versus chronic decrease).
The therapeutic approach and management of hypocalcemia dependslargely on the severity of symptoms and the underlying cause.In patients with asymptomatic hypocalcemia, it is important to verifywith repeat measurement (ionized or total calcium corrected for serumalbumin).
Calcium Conversions: | ||
| Calcium Chloride | 1 gram (10ml) = 273 mg elemental calcium = 13.6 mEq = 6.8 mmol. | 20mg of elemental calcium per mEq. 0.5 mmol of elemental calcium = 1.0 mEq. |
| Calcium Gluconate | 1 gram (10ml) = 93 mg elemental calcium = 4.65 mEq = 2.325 mmol. | 20mg of elemental calcium per mEq. 0.5 mmol of elemental calcium = 1.0 mEq. |
| Example conversion: | 0.075 mmol elemental calcium/kg/hr = 0.15 mEq/kg/hr= 3 mg/kg/hr. | |
Vitamin D: Reference Intakes /RDA
Source:https://ods.od.nih.gov/factsheets/vitamind/
Intake reference values for vitamin D and othernutrients are provided in the Dietary Reference Intakes(DRIs) developed by the Food and Nutrition Board (FNB)at the Institute of Medicine of The National Academies(formerly National Academy of Sciences). DRI is thegeneral term for a set of reference values used to planand assess nutrient intakes of healthy people. Thesevalues, which vary by age and gender, include:
- Recommended Dietary Allowance (RDA): averagedaily level of intake sufficient to meet thenutrient requirements of nearly all (97%–98%)healthy people.
- Adequate Intake (AI): established whenevidence is insufficient to develop an RDA andis set at a level assumed to ensure nutritionaladequacy.
- Tolerable Upper Intake Level (UL): maximumdaily intake unlikely to cause adverse healtheffects.
The FNB established an RDA for vitamin Drepresenting a daily intake that is sufficient tomaintain bone health and normal calcium metabolismin healthy people. RDAs for vitamin D are listed inboth International Units (IUs) and micrograms (mcg);the biological activity of 40 IU is equal to 1 mcg(Table 2). Even though sunlight may be a majorsource of vitamin D for some, the vitamin D RDAs areset on the basis of minimal sun exposure.
| Age | Male | Female | Pregnancy | Lactation |
|---|---|---|---|---|
| 0–12 months* | 400 IU (10 mcg) | 400 IU (10 mcg) | ||
| 1–13 years | 600 IU (15 mcg) | 600 IU (15 mcg) | ||
| 14–18 years | 600 IU (15 mcg) | 600 IU (15 mcg) | 600 IU (15 mcg) | 600 IU (15 mcg) |
| 19–50 years | 600 IU (15 mcg) | 600 IU (15 mcg) | 600 IU (15 mcg) | 600 IU (15 mcg) |
| 51–70 years | 600 IU (15 mcg) | 600 IU (15 mcg) | ||
| >70 years | 800 IU (20 mcg) | 800 IU (20 mcg) |
Calcium Supplementation Based on Age
Source:https://ods.od.nih.gov/factsheets/Calcium-QuickFacts/The amount of calcium you need each day depends onyour age. Average daily recommended amounts are listedbelow in milligrams (mg):
| Birth to 6 months | 200 mg |
| Infants 7–12 months | 260 mg |
| Children 1–3 years | 700 mg |
| Children 4-8 years | 1,000 mg |
| Children 9–13 years | 1,300 mg |
| Teens 14–18 years | 1,300 mg |
| Adults 19–50 years | 1,000 mg |
| Adult men 51–70 years | 1,000 mg |
| Adult women 51–70 years | 1,200 mg |
| Adults 71 years and older | 1,200 mg |
| Pregnant and breastfeeding teens | 1,300 mg |
| Pregnant and breastfeedingadults | 1,000 mg |
Upper limits - calcium:
Source:https://ods.od.nih.gov/factsheets/Calcium-QuickFacts/
The safe upperlimits for calcium are listed below. Most people do not get amountsabove the upper limits from food alone; excess intakes usually comefrom the use of calcium supplements. Surveys show that some olderwomen in the United States probably get amounts somewhat above theupper limit since the use of calcium supplements is common amongthese women.
| Birth to 6 months | 1,000 mg |
| Infants 7-12 months | 1,500 mg |
| Children 1-8 years | 2,500 mg |
| Children 9-18 years | 3,000 mg |
| Adults 19-50 years | 2,500 mg |
| Adults 51 years and older | 2,000 mg |
| Pregnant and breastfeeding teens | 3,000 mg |
| Pregnant and breastfeedingadults | 2,500 mg |
