What is the most appropriate next step for a 67-year-old woman with a palpable thyroid nodule?

The most appropriate next step for a 67-year-old woman with a palpable thyroid nodule is to obtain a TSH measurement and a thyroid ultrasound. This approach is essential because it helps assess the function of the thyroid and provides detailed imaging of the nodule's characteristics.

Measuring thyroid-stimulating hormone (TSH) levels is crucial in determining whether the nodule is functioning normally or if there are any abnormalities that may suggest hyperthyroidism or hypothyroidism. This information is critical in guiding further management.

Following the TSH measurement, a thyroid ultrasound is necessary to evaluate the nodule's size, shape, composition, and vascularity. These ultrasound features can help differentiate between benign and malignant nodules and inform decisions about possible fine needle aspiration (FNA) biopsy for cytological evaluation.

In comparison to the other options, scheduling follow-up in three months lacks immediate diagnostic information that could be critical in managing the potential risks associated with thyroid nodules, especially in an older patient, where the risk of malignancy is higher. MRI imaging of the head and neck is not typically indicated unless there is suspicion of local invasion or metastasis after further evaluation. Referring to an oncologist is premature without initial hormonal evaluation and imaging to determine the