## **Core Concept**
Corticosteroids are steroid hormones produced in the adrenal cortex that play a crucial role in regulating various physiological processes, including metabolism, immune response, and stress response. They are widely used in medicine for their potent anti-inflammatory and immunosuppressive properties. The effects of corticosteroids are diverse, impacting multiple systems in the body.

## **Why the Correct Answer is Right**
Corticosteroids are known to cause a range of effects including hyperglycemia (due to gluconeogenesis and insulin resistance), hypertension (due to mineralocorticoid effects and increased vascular tone), osteoporosis (due to effects on calcium metabolism and bone turnover), and immunosuppression (by affecting various immune cells). However, one effect that corticosteroids do not cause is a decrease in blood urea nitrogen (BUN); actually, they can cause an increase in BUN due to their effects on protein metabolism and renal function.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Corticosteroids can cause hyperglycemia. This is a well-documented side effect due to their role in promoting gluconeogenesis and causing insulin resistance.
- **Option B:** Corticosteroids can cause hypertension. This effect is partly due to their mineralocorticoid activity (leading to sodium retention and water retention) and direct effects on blood vessels.
- **Option C:** Corticosteroids can cause osteoporosis. Long-term use of corticosteroids leads to an imbalance in bone remodeling, resulting in decreased bone formation and increased bone resorption.
- **Option D:** This option is correct in the context of the question as it asks for "all except." The effects listed in A, B, and C are known side effects of corticosteroids.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that corticosteroids can cause a wide range of side effects, and their use should be carefully managed to minimize adverse effects. One classic side effect to remember is the potential for **osteoporosis** with long-term use, making bone protection strategies (like vitamin D and calcium supplementation) crucial.

## **Correct Answer:** D.