A 25-year-old female with depression symptoms requires initial evaluation. What diagnostic study is indicated?

The appropriate diagnostic study for the initial evaluation of a 25-year-old female presenting with symptoms of depression is thyroid stimulating hormone (TSH). This is crucial because depression can be a symptom of hypothyroidism, a condition where the thyroid gland does not produce enough hormones. Thyroid function tests, particularly TSH, are recommended in cases of new-onset depression to rule out any underlying endocrine disorders.

Hypothyroidism can mimic or contribute to depressive symptoms, including fatigue, weight gain, and changes in mood. An elevated TSH level, indicating an underactive thyroid, can help identify a treatable cause of depression. This initial screening can guide further management and treatment options, ensuring that any possible thyroid dysfunction is addressed before solely attributing the symptoms to major depressive disorder.

In contrast, prolactin, growth hormone, and cortisol levels may be relevant in specific contexts but are not standard initial screening tests for depression. Prolactin is primarily assessed in cases of suspected hyperprolactinemia, growth hormone testing is rarely indicated, and while cortisol levels might help in certain instances of suspected Cushing's syndrome, they are not routinely evaluated in typical depressive presentations. Thus, measuring TSH is the most appropriate first step in the evaluation of a