Excess pressure on the pulmonary arteries leads to the development of pulmonary hypertension. The life expectancy and prognosis for an individual with this condition has improved from what it was years ago, thanks to the availability of newer treatment alternatives and better technology.

There are several causes and risk factors underlying the development of pulmonary hypertension in individuals, and in most cases, it is a combination of factors rather than one isolated cause. As the disease begins to progress this can also change. When the cause for the condition is not known, it is called idiopathic pulmonary hypertension. This article addresses some of the causes and risk factors for pulmonary hypertension.

1. Blood diseases
Diseases affecting the blood flow out of the heart to the body can cause stacking of the blood or its backflow, increasing the pressure on the pulmonary veins. This can result in the development of pulmonary hypertension.

2. Hypoxic pulmonary vasoconstriction
Hypoxic pulmonary vasoconstriction is an integral physiological function that involves the narrowing of the blood vessels in the lungs while trying to divert the flow of the blood from the segments of the lung that are functioning poorly. In cases such as these, the blood flow is diverted from the poorly functioning parts of the lung to the segment where the tissues are working better. But in the case of sustained hypoxia, due to respiratory diseases or altitude, HPV can lead to the vessels on the pulmonary arterial side facing increased pressure, resulting in pulmonary hypertension.

3. Scarring and masses from other diseases
In some diseases, the blood vessels get remodeled and the lumen or the inner lining of the vessel tends to become narrower. This is a result of the inappropriate growth of the tissue around and inside the vessel. The scarring and masses from other diseases can narrow or compress the vessels, leading to the raised resistance of the blood flow, causing an increase in the pressure in them.

4. Parasitic infections
In some common parasitic infections, the blood vessels present in the lungs tend to get blocked due to the parasites, causing pulmonary artery hypertension.

5. Anti-obesity medications
There are rare cases in which the development of pulmonary hypertension has been reported due to the use of anti-obesity medications. This is one of the prime reasons why such medicines have been taken off the market entirely. Illegal, hard drugs like methamphetamines and cocaine can also result in severe forms of pulmonary hypertension.

6. Artery diseases
In addition to these, there are some types of diseases that can increase the pressure in the arteries, that in turn, leads to the development of pulmonary artery hypertension for no accurate reason. Unknown chemicals or toxins can result in the inappropriate or constricted growth of the tissues in or around the vessels. For example, portopulmonary hypertension is a condition that is caused due to the failure of the liver. When people suffering from it undergo a liver transplant, its symptoms disappear, pointing to evidence of the link between the malfunctioning of the liver and pulmonary hypertension. Other similar diseases can also be causes or risk factors for pulmonary hypertension.