This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: FMGE 2018, Subject name: Physiology
[{'content': 'Which of the following hormones regulates blood levels of 1,25-OH-cholecalciferol positively: \nSelect and explain. \nA. Thyroxine, B. Parathormone, C. Insulin, D. Calcitonin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: PTH - PTH acts in a positive feed forward manner in regulating vitamin D in response to | S. Ca At Ca2+ concentration below 9-10 mg /100 ml PTH promotes conversion of 25 -OH-cholecalciferol to 1,25 di OH cholecalciferol in the kidneys CALCITONIN - Peptide hormone secreted by thyroid gland - parafollicular cells / C. cells - Tends to decrease serum Ca level that is effect opposite to PTH INSULIN - Causes intracellular movement of plasma glucose | S. glucose', 'role': 'assistant'}]