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High blood pressure caused by an underlying condition is called secondary hypertension. Unlike regular high blood pressure, this is due to a specific medical condition – the most common are chronic kidney disease, sleep apnea, narrowed renal arteries or hormonal disorders such as primary aldosteronism.
An underlying cause should be suspected especially if blood pressure occurs early in life, rises suddenly or is difficult to control despite several medications. Through testing and investigation, the underlying cause can be identified and treated, which often provides significantly better control of blood pressure and reduces the risk of future complications.
High blood pressure is often discovered by chance. Perhaps during a health check at work, before an operation or when you seek care for something completely different. For many, it is primary hypertension, where several lifestyle and hereditary factors interact. But sometimes there is another explanation at the root: diseases that cause high blood pressure.
Diseases that cause high blood pressure - here are the most common ones to keep an eye on
When healthcare professionals talk about diseases that cause high blood pressure, they usually mean secondary hypertension. This means that blood pressure rises as a result of another medical cause, such as kidney disease, hormonal disorders or sleep apnea. Secondary hypertension is less common than primary hypertension, but it is important to find because treatment can sometimes be directed at the root cause itself.
The suspicion becomes stronger if blood pressure rises early in life, suddenly worsens, is unusually difficult to treat or if there are typical symptoms that do not quite fit into a common blood pressure disease. Resistant blood pressure values, i.e. when blood pressure remains high despite several medications, should especially make healthcare providers consider whether there is an underlying disease.
Kidney disease is one of the most common causes
The kidneys regulate the body's salt balance, fluid intake and several hormone systems that affect blood pressure. When kidney tissue is damaged, for example in chronic kidney disease, this regulation is impaired. It then becomes easier for the body to retain salt and fluid, and blood pressure rises.
This is a common situation in the clinic. A person with diabetes, previous kidney stone, recurrent urinary tract problems or hereditary kidney disease may develop high blood pressure as the first clear sign that the kidneys are under strain. Sometimes nothing is noticed at all until blood and urine tests show abnormal kidney values or albumin in the urine.
Typical findings that may indicate kidney-related high blood pressure are:
elevated creatinine or decreased kidney function
protein or albumin in the urine
swelling, especially in the legs or around the eyes
simultaneous diabetes or known kidney disease
This is where testing becomes central. Blood tests for kidney function and urine tests for albumin often provide more information than symptoms do, since kidney disease can be silent for a long time.
Hormonal disorders can drive up blood pressure
Among hormonal diseases, primary aldosteronism is particularly important to know. In this case, the adrenal glands produce too much aldosterone, a hormone that causes the body to save sodium and lose potassium. The result is often high blood pressure, sometimes together with low potassium, but many people have normal potassium and can still have the disease. Primary aldosteronism is now considered one of the main causes of secondary high blood pressure. Therefore, screening is recommended for several risk groups, especially in treatment-resistant hypertension.
This is a good example of why "ordinary" high blood pressure sometimes needs to be investigated more carefully. A patient who needs three or four medications to get reasonable blood pressure values, or who experiences muscle fatigue and low potassium, may have a treatable hormonal cause. Primary aldosteronism can sometimes be treated with targeted medications and in some cases surgery.
Other hormonal causes are less common but classic to recognize. Cushing syndrome involves too high cortisol levels and can cause weight gain over the abdomen, muscle weakness, thin skin and purple stretch marks. Thyroid disorders, both over- and under-function, can also affect blood pressure. Pheochromocytoma, which is a rare catecholamine-producing tumor, can cause attacks of headache, palpitations and sweating along with severe increases in blood pressure.
Sleep apnea is an often overlooked explanation
Obstructive sleep apnea means that the upper airway collapses during sleep so that breathing is repeatedly disrupted. The body reacts with stress, oxygen deprivation in short episodes and increased activation of the nervous system and hormonal system that raises blood pressure. Therefore, sleep apnea is a well-known cause of secondary hypertension and is particularly common in treatment-resistant blood pressure disease.
Many people seek treatment not for sleep but for fatigue. They describe falling asleep on the couch, waking up with morning headaches or feeling inexplicably sluggish even though they think they have slept all night. A partner may report loud snoring, pauses in breathing, or gasping for air in their sleep.
Narrowing of the renal arteries can cause sudden or difficult-to-treat high blood pressure
Sometimes high blood pressure is not due to damaged kidney tissue, but to reduced blood flow to the kidney. This is called renovascular hypertension and is often caused by narrowing of the renal arteries. In younger people, it may be due to fibromuscular dysplasia, while in older people it is more often due to atherosclerosis.
When the kidney senses that blood flow is too low, the renin-angiotensin-aldosterone system is activated, which raises blood pressure to "save" the circulation. This can cause blood pressure to rise quickly, worsen unexpectedly, or become difficult to control. Healthcare professionals may especially suspect this if kidney function deteriorates after taking certain blood pressure medications, if the patient has recurrent unexplained heart failure or sudden episodes of pulmonary edema, or if there is other clear vascular disease.
It is not a cause for which everyone with high blood pressure is screened widely. But in the right situation, it is important to consider it, since continued investigation with imaging diagnostics and targeted treatment may be relevant.
When should one suspect that high blood pressure has an underlying disease?
It is easy to wonder whether high blood pressure is an isolated condition or a sign of an underlying cause. The answer is rarely about a single symptom, but about the pattern in the medical history, test results and how the pressure develops over time. Suspicion of secondary hypertension is raised above all in the event of early onset, sudden deterioration, very high blood pressure levels or when the pressure is difficult to lower despite several medications.
The following situations should attract extra attention:
blood pressure is high despite three medications, or requires four to be controlled
blood pressure rises suddenly after previously being stable
you have low potassium, abnormal kidney values or protein in the urine
you snore heavily, have shortness of breath or pronounced daytime fatigue
you get attacks with headaches, sweating and palpitations
you have clear signs of hormonal disorders, such as central weight gain, muscle weakness or skin changes
The investigation often starts quite simply. Blood pressure needs to be measured correctly and preferably confirmed with repeated measurements, sometimes even at home or with 24-hour measurements. The doctor can then choose blood tests, urine tests and in some cases hormone tests or imaging diagnostics depending on what is suspected.
There is also a practical point here: high blood pressure often causes few or no clear symptoms. This is why health checks are valuable, both for private individuals and in the workplace. An elevated blood pressure can be the first signal that the body is already showing signs of kidney damage, sleep disorders or hormonal imbalance before you yourself have time to react.
A blood pressure value is therefore not just a number. In the best case, it is a chance to detect something in time, while measures can still make a big difference for the heart, brain, kidneys and work capacity.
