Medications
The primary medications used for GERD are proton-pump inhibitors, H2 receptor blockers and antacids with or without alginic acid. The use of acid suppression therapy is a common response to GERD symptoms and many people get more of this kind of treatment than their case merits. The overuse of acid suppression is a problem because of the side effects and costs. Proton-pump inhibitors
Proton-pump inhibitors (PPIs), such as omeprazole, are the most effective, followed by H2 receptor blockers, such as ranitidine. If a once-daily PPI is only partially effective they may be used twice a day. They should be taken one half to one hour before a meal. There is no significant difference between PPIs. When these medications are used long term, the lowest effective dose should be taken. They may also be taken only when symptoms occur in those with frequent problems. H2 receptor blockers lead to roughly a 40% improvement. Antacids
The evidence for antacids is weaker with a benefit of about 10% (NNT=13) while a combination of an antacid and alginic acid (such as Gaviscon) may improve symptoms by 60% (NNT=4). Metoclopramide (a prokinetic) is not recommended either alone or in combination with other treatments due to concerns around adverse effects. The benefit of the prokinetic mosapride is modest. Other agents
Sucralfate has similar effectiveness to H2 receptor blockers; however, sucralfate needs to be taken multiple times a day, thus limiting its use.
PTH up-regulates 25-hydroxyvitamin D3 1-alpha-hydroxylase, the enzyme responsible for 1-alpha hydroxylation of 25-hydroxy vitamin D, converting vitamin D to its active form (1,25-dihydroxy vitamin D). This activated form of vitamin D increases the absorption of calcium (as Ca2+ ions) by the intestine via calbindin. PTH was one of the first hormones to be shown to use the G-protein adenylyl cyclase second messenger system. Regulation of serum phosphate
PTH reduces the reabsorption of phosphate from the proximal tubule of the kidney, which means more phosphate is excreted through the urine. However, PTH enhances the uptake of phosphate from the intestine and bones into the blood. In the bone, slightly more calcium than phosphate is released from the breakdown of bone. In the intestines, absorption of both calcium and phosphate is mediated by an increase in activated vitamin D. The absorption of phosphate is not as dependent on vitamin D as is that of calcium. The end result of PTH release is a small net drop in the serum concentration of phosphate. Vitamin D synthesis
PTH upregulates the activity of 1-α-hydroxylase enzyme, which converts 25-hydroxycholecalciferol, the major circulating form of inactive vitamin D, into 1,25-dihydroxycholecalciferol, the active form of vitamin D, in the kidney. Interactive pathway map
Regulation of PTH secretion
Secretion of parathyroid hormone is determined chiefly by serum ionized calcium concentration through negative feedback. Parathyroid cells express calcium-sensing receptors on the cell surface. PTH is secreted when [Ca2+] is decreased (calcitonin is secreted when serum calcium levels are elevated).