Final answer:
Lithium can cause hypothyroidism, manifesting as fatigue, weight gain, and cold sensitivity, as well as potentially increasing the risk of goiter development in patients.
Step-by-step explanation:
In patients on lithium, thyroid dysfunction can typically manifest as hypothyroidism. Lithium treatment is known to potentially affect thyroid function, leading to an underproduction of thyroid hormones. This can cause symptoms such as fatigue, weight gain, sensitivity to cold, and reduced mental activity. Long-term lithium use may also increase the risk of developing a goiter, which is an enlargement of the thyroid gland. Understanding the influence of lithium on thyroid function is essential for managing the health and treatment strategies for patients using this medication.