What is a common side effect of corticosteroid therapy?

Corticosteroid therapy is known to result in specific side effects due to the pharmacological actions these drugs have on the body. Weight gain and fluid retention are common side effects because corticosteroids can increase appetite and alter the way the body retains sodium and excretes potassium. This results in increased body weight due to both increased caloric intake and fluid accumulation in tissues.

In the context of corticosteroid use, the other side effects listed, such as fatigue, nausea, and headache, are not as distinctive or frequently reported as weight gain and fluid retention. While corticosteroids can lead to fatigue in some individuals as a result of other underlying conditions or medication effects, it is not as commonly recognized. Nausea and headache may occur but are less characteristic and can be caused by a multitude of reasons unrelated to corticosteroid therapy. Therefore, the specific combination of weight gain and fluid retention stands out as a hallmark side effect of corticosteroids, making it the most appropriate choice in this context.