Vitamin D is essential for regulating calcium and phosphate metabolism, and its deficiency or excess can significantly affect parathyroid function. The deficiency or insufficiency of vitamin D can lead to increased parathyroid hormone (PTH) production, resulting in secondary hyperparathyroidism. Conversely, adequate vitamin D levels suppress PTH synthesis and maintain normal calcium levels. Dysregulation of this delicate balance can contribute to various disorders such as osteoporosis, renal stones, and skeletal abnormalities. Hence, understanding the complex interactions between vitamin D and the parathyroid glands is important for diagnosing and managing disorders such as primary and secondary hyperparathyroidism.