Final answer:
Secondary hypertension results from an identifiable underlying condition, unlike primary hypertension with no clear known cause. 'No clear known cause' is the correct answer as all other options listed are known causes of secondary hypertension.
Step-by-step explanation:
The correct option is 2:
Secondary hypertension (HTN) may result from any of the following, EXCEPT:' is option 2) no clear known cause. Secondary hypertension is the term used when high blood pressure is the result of another condition. Most cases of hypertension (about 90%) are primary, also known as essential hypertension, where the exact cause is generally unknown and attributed to a mix of genetic and lifestyle factors. Pregnancy, on the other hand, can cause gestational hypertension, which is a form of high blood pressure that occurs during pregnancy but usually resolves after giving birth.
In contrast, the remaining cases are classified as secondary hypertension, which is due to identifiable causes such as chronic kidney disease, endocrine disorders, or conditions related to pregnancy. These specific conditions are known to cause elevations in blood pressure, distinguishing secondary hypertension from primary hypertension where no clear cause can be identified.