What is Hypoparathyroidism?

Hypoparathyroidism (HPTH)
is a rare disorder that is characterized by the lack of (or in a few cases the inadequate effect of) parathyroid hormone.
The function of the hormone is very complicated and involved in many difficult biochemical processes.

Physiology:
The parathyroid glands are four tiny, nearly white glands with a weight of approximately 30 mg each. It is well documented that all humans have at least four of theses glands, while just about 4% have more than four.
Usually there are two on each side of the throat, behind the upper and lower part of the thyroid. The location of specially the two lower may vary. They are separate endocrine glands in our body and are NOT related to the thyroid (except they are neighbors in the neck).
The parathyroid hormone (PTH) is made in these glands. The PTH hormone is essential to life and consists of 84 amino acids. The hormone acts on receptors on the cell-surface and the PTH receptors are G-linked like Insulin. The amounts of receptors are not constant but vary in the opposite proportion to the amount of PTH in the blood. The PTH hormone stimulates the activity of certain genes and ways of transcription. It is important for normal cellular differentiation and growth.
The receptors are found in the kidneys, bones, lungs, intestines, brain, heart and many other tissues.
A lot of researches are still being made on the function of the hormone.

The regulation of calcium in the blood:
The PTH hormone is the most important "minute to minute" fine regulator of blood calcium in the body. ½ % of the calcium in the body is ionized calcium in the blood, which is essential to life. It is both an electrolyte and a hormone itself. The ionized calcium is essential to the life within and between our cells, this is why it is the only electrolyte in the body that is hormone regulated (PTH). The blood calcium is therefore regulated within a very tiny narrow range to ensure the optimal function of body cells.

The PTH hormone regulates ionized active calcium by:

1. Directly reabsorbing ionized calcium from the kidneys.
2. Activating the vitamin D hormone, that absorbs calcium from the intestines.
3. Promotes the formation of cells which constructs and dissolve bone tissue.
4. Mobilizes ionized calcium from the bones to the blood, when our cells need more calcium.

A normal amount of calcium in the blood is important to many essential processes in the body:

1. Providing the electrical energy for muscle contractions.
2. Providing the electrical energy for all our nerves.
3. Neuromuscular contractions.
4. The contractions of the heart.
5. Blood coagulation.
6. Hormone and neurotransmitter release.
7. Building of bones.

The normal range of calcium in the blood is the normal range of a healthy population (98%) It is important to notice that a healthy person has specific value within this normal range and that the individual variations not vary more than 2% from this "set point".
The cells in the parathyroid glands have sensors that all the time monitors the calcium level in the blood. The PTH hormone is produced all the time. If the blood calcium level goes down, more PTH is produced. If blood calcium goes up, less PTH is produced.
Approximately 40% of the total calcium in the blood is in the form of active ionized calcium.

Calcium-ions ( electrolyte) and homeostasis:

Few people are aware of the fluctuations of ions (electrolytes) that are in our blood stream. Every minute of the day and night these tiny electrical particles smoothly fluctuate in response to exercise, perspiration, infections and what we eat. The most important ions are calcium, potassium and salt.

As all animals the human beings survive these small fluctuations. The ion levels in our blood stream and inside our cells are kept steady through an intricate and balanced system.

If not for this system, known as homeostasis, the ion levels would bring our body into chaos and death.

The calcium ions are mainly regulated by the Parathyroid hormone (PTH). The lack of PTH brings our body out of balance (homeostasis). The calcium in our blood and within our cells becomes unstable and low.

Absorption of Magnesium from the intestines becomes reduced when we lack PTH.

Excretion of Phosphate from the kidneys is lowered when we lack PTH.