Calcium composes 1.5% of body weight, i.e. it weighs around 1,160 gr. Ninety-nine percent (99%) of body calcium is found in bone in the form of calcium phosphate and 1% in teeth, skin and blood plasma. Sixty percent (60%) of plasma calcium is in the ionized form, Ca++, in which case it is biologically active, and 40% is bound to albumin.
The functions of calcium as a nutrient
- It has a structural role, contributing along with phosphorus to bone building
- It has a role in blood clotting (coagulation); its presence is essential for the conversion of prothrombin to thrombin
- Muscle contractility
- Reduction of neuromuscular excitability
- Conservation of heart muscle contractility
- Essential for hormone production
- Essential for hormone activity and secretion
- Essential for the conservation of cell membrane functionality
- Activates various enzymes of the human organism
Daily body needs in calcium
- Infants: 360 – 540 mg
- Children: 1200 mg
- Adults: 1000 – 1200 mg
- Pregnant / nursing mothers: 1400 –1600 mg
- Athletes: 1600 – 2000 mg
Calcium absorption by the body
Factors inhibiting calcium absorption of calcium are:
- Vitamin D deficiency or resistance
- Magnesium deficiency
- Renal failure
- Increasing age
- Taking corticosteroids
- Reduced levels of oestrogen as in menopause
Problems caused by calcium deficiency
- Delayed growth among children
- Weak or deformed bones, tooth decay
- Skeletal dysplasia manifesting as e.g. rickets (in children), osteomalacia, osteoporosis
- In chronic hypocalcaemia, cataracts and calcification of the basic ganglia have been observed
Symptoms due to low blood calcium levels – hypocalcaemia
- muscle spasms
- paraesthesias, i.e. tingling or ‘pins and needles’ sensation around the mouth
- tetany and numbness in the limbs
- hyperactive tendon reflexes
- life-threatening complications
- cardiac arrhythmias / dysrrhythmias
- muscle weakness
- seizures / spasms
- electrocardiographic (EDG) changes
Treatment for low blood calcium levels – hypocalcaemia
Treatment is with tablets (one tablet or a combination of more than one) taken orally in accordance with the severity of symptoms; thereafter, the calcium levels in the blood are monitored. Occasionally the treatment may be long-term, this depending upon the cause. Since the alterations in blood calcium levels may reverse quickly, close collaboration between the patient and the endocrinologist is a must. In emergencies, the patient needs to be hospitalized for intravenous medication.
Symptoms due to elevated blood calcium levels – hypercalcaemia
- Neurological disorders
- Weakness, fatigue
- Bone and muscle problems
- Loss of appetite
- Nausea, vomiting, constipation
- Thirst, increased urinary frequency
- Disturbance of consciousness
- Kidney stones
Hyperparathyroidism is hyperactivity of the parathyroid glands (four glands behind and near the thyroid gland), resulting in excessive production of parathyroid hormone (PTH).
Parathyroid hormone regulates the levels of calcium and phosphorus in the body and contributes to their maintenance. Excessive secretion of parathyroid hormone may be due to problems in the glands, and in this case it is called “primary hyperparathyroidism”, which leads to hypercalcaemia (i.e. elevated calcium levels).
It may also appear as a response to low levels of calcium, this being encountered in such conditions as vitamin D deficiency or chronic renal failure. This is referred to as “secondary hyperparathyroidism”. In each and every case, the increased levels of parathyroid hormone are detrimental to bone health and treatment is often necessary.
Recent data have revealed that deficiency of vitamin D plays a role in the development of hyperparathyroidism.
Categories of hyperparathyroidism:
– Primary hyperparathyroidism
This refers to the hyperactivity of the parathyroid glands, which brings about excessive secretion of parathyroid hormone (increased values), the result being the increase of calcium levels in the blood. Common causes are adenomas, hyperplasia or, more rarely, carcinoma of one or more parathyroid glands.
– Secondary hyperparathyroidism
This is the reaction of the parathyroid glands to hypercalcaemia (low blood calcium levels) that arises from other causes (non-parathyroid), e.g. chronic renal failure.
– Tertiary hyperparathyroidism
This is hyperparathyroidism from hyperplasia of the parathyroid glands due to non-response of the calcium levels. It is a disorder that occurs more frequently in patients with chronic renal failure.
Treatment of increased calcium due to hyperparathyroidism
The endocrinologist decides whether or not he will recommend medication since there exist mild cases without any clinical sequelae for the patient: in these instances, no medication is required and the patient will merely need monitoring.
The type of treatment is applied in accordance with the cause, and, in many cases, is dependent upon the patient’s age, any other illnesses s/he may have and their general physical condition.
Treatment for hyperparathyroidism, based on the abovementioned factors, may be surgical or with tablets. Not all people meet the criteria for surgery. Moreover, very thorough radiological investigation and localization is needed as regards the hyperactivity of the parathyroid glands. Mostly the experienced surgeon will find the hyperactive gland(s) himself during surgery, even though it is advisable for him to know beforehand where the incision will be made. During the intervention, the surgeon is also able to determine with accuracy the result of the operation on the patient’s blood calcium levels.
Medication is not always a panacea and does not invariably provide a permanent resolution of the problem. Nevertheless, it offers relief to certain groups of patients, this based on the above criteria.
As mentioned on the relevant information page, osteoporosis is regarded as a disease because of the disruption of calcium metabolism in the bones, which causes a steady reduction over time in bone density. Normal blood calcium values are not markers for determining the health of the bones.