BB5CSP Cell Signalling and Physiology Case study 1.If this condition, is left untreated then it can lead to mortality. If the person is suffering from kidney disease then his serum calcium and parathyroid levels (PTH) are checked. Serum calcium level test is that test in which the amount of calcium in the blood is estimated and this serum calcium test is mainly used to screen the bone diseases or the disorders that are regulated by calcium which includes kidney diseases or renal failure. The normal serum calcium level is 8.6-10.2 mg/dl (Sofronescu, 2019) but in the 65-year old person, the serum calcium level can be less than the normal range because he is suffering from kidney disease and due to this kidney failure the production of the vitamin D also gets reduced which helps to absorb the calcium from the food and thus results in low levels of the calcium in the body of the 65-year old patient. Furthermore, due to kidney failure, the kidney is unable to remove the extra phosphorus from the blood which results in low levels of serum calcium in the body (Sofronescu, 2019). The normal parathyroid level is 10-65 pg/ml (Khatri, 2021). In a 65-year old person, the levels of parathyroid level are high than the normal range because the kidney failure leads to the increased level of parathyroid level due to the excess of the phosphorus in the body of the person and the low amount of calcium mainly due to the no production of the vitamin D which is used to absorb the calcium (Yuen, 2016). 2.The endocrine system largely controls or regulates the secretion of each hormone, further the secretion of the hormone depends upon the amount of the hormones that are already present in the blood or on the amount of the other substances in the blood like calcium. Parathyroid hormone is also known as the parathormone, four parathyroid glands, which are tiny glands in the neck behind the thyroid gland, secrete parathyroid hormone. Furthermore, the amount of calcium in the body affects or controls the levels of the parathyroid hormone in the blood. If the low amount of calcium is present in the body then this low amount further stimulates the excess of the secretion of the parathyroid hormone in the blood whereas the high amount of calcium levels in the blood prevents the secretion of the parathyroid hormone level in the blood (Yuen, 2016). And in the case of kidney disease, the serum calcium levels are low in the blood which elevates the secretion of the parathyroid hormone in the body (Kumar and Thompson, 2010). Two types of cells are found in the parathyroid gland, one is the chief cell and another is the oxyphil cell. The number of oxyphil cells increases in the number when the person is suffering from chronic kidney disease. The cells which play a significant role in the secretion of the parathyroid hormone are the parathyroid chief cells, these cells. The chief cells contain