Many people worry about having too much cortisol, since elevated levels of cortisol can lead to weight gain, fatigue, and more serious symptoms. But having too little cortisol can be just as harmful to your health. If your adrenal glands are damaged or if you have adrenal fatigue syndrome, your body might not be producing a sufficient amount of cortisol to properly regulate your blood pressure and immune system. Here are common symptoms of cortisol deficiency:  Weight loss and low appetite Low blood pressure Fainting Fatigue Low levels of energy even when rested Vomiting, nausea and gastrointestinal pain Salt cravings   Hyperpigmentation (dark spots on the skin) Muscle weakness or pain Irritability and depression Heart palpitations Lack of enthusiasm For women, body hair loss and decreased libido If you suspect your cortisol levels are low, make an appointment with your doctor to schedule a cortisol test. A cortisol test involves having your blood drawn and sent to a lab to check cortisol levels. Cortisol levels are usually highest in the morning and lower in the afternoon and evening, and in some cases your doctor might decide to test you twice in the same day to compare morning and afternoon levels. Your doctor will be able to determine whether you have low cortisol or Addison's disease by comparing your levels to normal cortisol levels.   There are several ways of testing cortisol including saliva, blood, and urine tests. Additionally, your doctor may test for other hormones like TSH, free T3, T4, total thyroxine, DHEA, and 17-HP, which can be precursors to cortisol.  The "normal" range varies from lab to lab, but in general, the average morning level for an adult or child is 5–23 micrograms per deciliter (mcg/dL), or 138–635 nanomoles per liter (nmol/L). The average afternoon level for an adult or child is 3–16 mcg/dL or 83–441 nmol/L.  Be sure to get your cortisol levels tested by a physician, rather than using an at-home method. Saliva testing kits advertised online are not as reliable as blood tests...

How would you rephrase that briefly using Vietnamese?
Chú ý xem bạn có các triệu chứng thiếu hụt cortisol không. Xét nghiệm nồng độ cortisol. Xác định nguyên nhân dẫn đến mức cotisol thấp.