- Normal serum 1,25-dihydroxyvitamin D in patients with medullary carcinoma of the thyroid. Lee, S., Morimoto, S., Onishi, T., Tsuji, M., Okada, Y., Seino, Y., Ishida, M., Yamaoka, K., Takai, S., Miyauchi, A., Kumahara, Y. J. Clin. Endocrinol. Metab. (1982)