Medical Biology: Oncology and Renal Physiology

Addison's disease causes postural hypotension. Other causes include phaeochromocytoma, Conn's disease and other drugs such as the oral contraceptive pill (OCP) and steroids.

There are characteristic features of iritis, however, including the stuck گdown pupil.

CA 125 is a mucin-type glycoprotein which is usually not expressed by mucinous tumors. The antigen (CA 125) is expressed by fetal amniotic and coelomic epithelium.

Commonly, the dose of a drug is reduced when there is renal impairment to prevent the accumulation of the drug. It is also common to reduce the frequency of the doses.

Patients with hyponatremia commonly have no symptoms, but it is still important to treat the condition because if it is untreated, symptoms and serious problems can arise.

Mutations in the BRCA 1 gene (located on chromosome 17) cause most of the ovarian epithelial cancers seen on a hereditary basis.

Adenocarcinoma is a cancer arising from the mucosa of the rectum. Cancer cells can also spread from the rectum to the lymph nodes on their way to other parts of the body. RET mutation is responsible for adenocarcinoma
RET mutation is responsible for increased risk of medullary thyroid cancer, as well as multiple endocrine neoplasia 2, in which pheochromocytoma and parathyroid adenoma also occur.

Immature teratomas of the ovary are rare germ cell malignancies. These are frequently diagnosed in girls and young women up to their early 20s.
Dysgerminomas, the most frequent germ cell malignancy, are principally solid. Such tumors are most frequent in women with dysgenetic gonads. Pure ovarian dysgerminomas cause an elevated LDH with normal hCG and a-fetoprotein levels..

Amiloride inhibits the reabsorption of sodium in the collecting ducts and so also blocks the potassium secretion at this point in the nephron. The result is that amiloride can reduce overall potassium excretion and potassium depletion does not occur. 

ANP stands for atrial natriuretic peptide. It is made in the atrial cells in the heart and in some cells in the kidney. It can increase sodium excretion by inhibiting collecting duct sodium reabsorption. However, it probably does not play an important role in the normal regulation of sodium excretion.

This renal disorder arises from a mutation of the receptors for ADH (anti diuretic hormone or vasopressin) or the aquaporins which are water channels.
In Barrter's syndrome, there is a mutation which inhibits the activity of the NaK2Cl cotransporter, which is the molecule normally inhibited by frusemide. The clinical effects of Barrter''s syndrome are therefore the same as excess frusemide and include loss of sodium, potassium and water. The body's response to this is to raise aldosterone levels in an attempt to conserve sodium.

In particular, there can be a failure of reabsorption of sodium in the proximal tubule. This results in excess sodium reaching the collecting ducts where some of it is exchanged for potassium, causing excess potassium loss and a low plasma potassium level. Hence, there is a loss of bicarbonate .

Body osmolality is sensed in the hypothalamus by osmoreceptors which influence thirst (water intake) and ADH (anti-diuretic hormone or vasopressin) secretion (which influences water output by the kidneys). 

In psychogenic polydipsia, prolonged excess water intake can lower plasma osmolality by a dilutional effect. Despite the kidneys efforts to produce a dilute urine, the patients intake of water may exceed the kidneys output of water and so dilute urine.

In nephrogenic diabetes insipidus, there is adequate ADH, but the kidney is unable to respond to the ADH. Nephrogenic diabetes insipidus can arise as a side effect of certain drugs, especially lithium which is used to treat manic depression.
Changes in plasma osmolality are poorly tolerated, especially by nerve cells, so plasma osmolality is tightly regulated. If renal water reabsorption is inadequate then there will be excess water loss in the urine and plasma osmolality will rise and vice versa. Central diabetes insipidus is characterised by low plasma osmolality.