HUMAN CHORIONIC GONADOTROPHIN

Human chorionic gonadotrophin (HCG) is synthesised early in pregnancy by the newly formed trophoblasts and is secreted into the maternal circulation. It can be detected as early as the eighth day after conception (this property help in quick detection of pregnancy) and its levels in the maternal blood continue to rise rapidly, reaching peak levels at about 10-12 weeks of gestation. HCG measurements have long been used to confirm pregnancy and many "home-test" kits are widely available. Pregnancy kits detecting urine HCG are not as sensitive as those measuring plasma or serum HCG levels the glycoprotein is rapidly metabolised by the liver and kidneys and only a small fraction is excreted unchanged in the maternal urine. HCG has luteotrophic activity and is responsible for maintaining the viability of the corpus luteum into early pregnancy. It may also be responsible for inducing testosterone secretion by the fetal testes before the fetal pituitary is ready to secrete luteinising hormone. Serum HCG titres are also used in the investigation of a probable ectopic pregnancy high titres suggest it as the cause of acute abdominal pain, which is usually the presenting symptom. HCG is also produced by tumours of the trophoblast and thus can occur in males (e.g., testicular teratocarcinoma) and non-pregnant females (e.g., hydatidiform mole and choriocarcinoma).

INSIGHT ON WILEON'S DISEASE

Wilson's disease is an inborn error of copper metabolism characterised by deposition of copper in, and damage to, the liver (cirrhosis), brain basal ganglia, proximal renal tubule (Fanconi syndrome), and the cornea of the eye (Kayser-Fleischer rings). The plasma caeruloplasmin level is usually low and the urinary copper level high, reflecting the high level of plasma free copper. The definitive diagnosis depends on demonstration of excess copper in the liver.

FOLATES

Folates are a naturally occurring group of substances, found in green vegetables and meat, that are structural derivatives of the parent compound folic acid (pteroylglutamic acid).
The different folate compounds are involved in the transfer of one-carbon groups, primarily as methyl or formyl moieties; hence their importance in metabolic pathways involving one-carbon transfers such as the synthesis of methionine, purines, and thymidylate monophosphate (component of DNA).
The characteristic clinical presentation of folates deficiency is megaloblastic anaemia. The causes are manifold including malabsorption, dietary deficiency, and increased requirements (growth, pregnancy, lactation).

PRODUCTION OF GASTRIN

Gastrin is produced by the G-cells of the gastric antrum and to a lesser extent, the duodenum.Two major (and several minor) forms are found in the gastrin-producing tissues and in the circulation, 'big' gastrin (half-life -40 min) and 'little' gastrin (G17, half-life -8 min). Both forms stimulate the secretion of gastric acid and increase gastric antral motility. Excessive amounts are secreted by gastrinomas and are responsible for the Zollinger- Ellison syndrome.

NUTRITIONAL EFFECTS OF FORMULA FEEDING

A variety of formulas are available for feeding infants. The most commonly used formulas are from bovine milk, and nutrient specifi cations for infant formulas are available. Commercially available formulas are recommended when breastfeeding is not chosen. Cow’s milk is not recommended in the fi rst year of life because of its nutritional limitations and inappropriate nutrient concentrations. Cow’s milk has higher concentrations of protein and phosphorus, a lower calcium-to-phosphorus ratio, limited iron, less essential fatty acids, vitamin C, and zinc than human milk. Increased renal solute load due to cow’s milk and increased occult blood loss via the gastrointestinal tract leading to iron defi ciency and anemia in infants fed cow’s milk not supplemented by other nutrients are additional reasons to discourage the feeding of cow’s milk in early infancy.