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Parathyroid hormone


Parathyroid hormone (parathyroid hormone) is one of the main regulators of calcium in the blood. This hormone is very useful information for: parathyroid disease (primary hyperparathyroidism, secondary hyperparathyroidism, autoimmune hypoparathyroidism), osteoporosis, calcium content disorders (hypercalcaemia, hypocalcaemia).
Parathyroid hormone is a protein that is synthesized in the parathyroid glands. It main function is to regulate calcium metabolism in the body.  When the level of calcium in the blood falls, the parathyroid hormone increases to raise the calcium concentration in the blood by sending signals to the bone to:
1. inhibit collagen synthesis in active osteoblasts; 
2. activate osteolysis by osteocytes; 
3. increase osteolysis by the osteoclasts;
4. increase in the rate of maturation of progenitor cells, differentiating into osteoblasts and osteoclasts.
As a result, the calcium level in the blood rises. However, one of the notable effects of parathyroid hormone is phosphaturia (excretion of phosphorus in the urine), because of a decrease in tubular reabsorption of phosphate. This leads to decalcification of the bone and the release of calcium and phosphorus into the blood. Parathyroid hormone also increases calcium absorption in the intestine. 
Preparation for diagnosis
  • The patient is explained that the analysis is necessary to evaluate the function of parathyroid glands.
  • It is necessary to explain to the patient about the need for fasting, on the evening before the blood is taken, as eating food distorts the result of the analysis.
  • The patient is warned that the analysis requires taking blood from the vein.
  • Warn about possible unpleasant sensations during the application of the tourniquet to the arm and the puncture of the vein and also explain that the procedure for taking blood will take only a few minutes. 
Procedures
  • After venepuncture, blood is collected into a test tube with Ethylenediaminetetraacetic acid (EDTA).
  • Place the venepuncture with a cotton ball until the bleeding stops.
  • In the formation of hematoma at the venepuncture site, prescribe hot compresses.
  • After the blood is taken, the patient can again switch to his normal diet.

Reference Values
Age
Content of ng / l
Children aged 2 to 20 years
9 – 52
Adults
10 - 65
  
Factors influencing the result of the study
  • Factors that distort the result
    • Failure to comply with the requirements for the study (the need to refrain from eating, starting from the evening before taking blood).
    • Haemolysis of the blood sample. 
  • Factors that increase the result
    • Anticonvulsants.
    • Corticosteroids.
    • Isoniazid.
    • Lithium.
    • Phosphates (increase result to 125% in 1 hour after ingestion of 1 g).
    • Rifampin. 
  • Factors that lower the result
    • Cimetidine.
    • Propranolol  
Purpose of the study
  • Differential diagnosis of parathyroid gland diseases.
Deviations from the normal
Elevated levels of parathyroid hormone and calcium in serum indicate primary or secondary hyperparathyroidism. The lowered level of parathyroid hormone indicates hypoparathyroidism, but it can also be observed in some malignant tumors.
Clinical significance of parathyroid hormone disorder:
Pathological condition 
Causes 
Level of parathyroid hormone 
Level of calcium
Ca2+ 
Primary hyperparathyroidism
Adenoma or parathyroid cancer. 
high 
From high to normal 
Secondary Hyperparathyroidism
Chronic kidney disease. Severe insufficiency of vitamin D. Rickets. Malabsorption of calcium. Pregnancy and lactation. 
high
Low 
Tertiary  
Hyperparathyroidism
Prolonged secondary hyperparathyroidism with progressive course. 
high
From high to normal 
hypoparathyroidism
Accidental removal of parathyroid glands. Autoimmune lesion. 
Low 
Low 
Malignant tumors 
Squamous cell carcinoma of the lung. Cancer of the kidney, pancreas or ovary.
From high to normal
low


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