Transferrin is produced by the liver and is a major protein that regulates the absorption and transportation of iron into and throughout the blood and body respectively. High levels of transferrin saturation are indicative of iron overload whilst low levels may coincide with iron deficiency.

A total iron-binding capacity (TIBC) test measures the blood's ability to attach itself to iron and transport it around the body. Individuals with iron deficiency will have low levels of iron but a raised TIBC. In comparison, those that have possess too much iron, for instance, in patients with iron overload syndrome, iron will be elevated but TIBC will be reduced or normal.

Measuring the amount of iron present in the blood is important in the diagnosis of conditions such as iron deficiency anaemia caused by a lack of iron to haemochromatosis which is caused by an overload of iron. Common symptoms of both elevated and reduced levels of iron include; muscle weakness, difficulty concentrating and fatigue. Other causes of reduced iron besides anaemia can be due to general blood loss. In contrast, a raised result can be indicative of an iron overload syndrome which may be the result of an inherited condition that results in the body storing too much iron, or the excessive consumption of iron supplements.

Ferritin is a protein that stores iron and releases it in a controlled fashion. In humans, it acts as a buffer against iron deficiency and iron overload. Plasma ferritin is also an indirect marker of the total amount of iron stored in the body, hence serum ferritin is used as a diagnostic test for iron-deficiency anaemia. Low levels are indicative of anaemia and may be caused by events such as excessive bleeding or lack of iron within the diet. In contrast, elevated ferritin levels could indicate iron overload syndrome or liver damage.

Interestingly enough, vitamin D is in fact a hormone that is produced by the body and requires exposure to sunlight for activation. In addition. it can be found in certain foods such as egg yolks, fish and fortified dairy and grain products. Vitamin D is an essential component required for maintaining bone strength due to its role in aiding the intestines ability to absorb calcium. Low levels of vitamin D may be associated with secondary low bone mineral density and hyperparathyroidism. Consequently, these patients have a greater risk of suffering fractures and osteoporosis. Other conditions such as rickets and osteocalcin may also develop as a result of continued vitamin D deficiency over a long period of time.

The purpose of this test is to measure the amounts of free thyroxine (T4) that is present within the blood. T4 is a one of two hormones that is secreted by the thyroid gland. Therefore, a high result may be associated with an individual with an overactive thyroid as more T4 is produced then normal. In contrast, a lower than normal result may arise if an individual has an underactive thyroid.

Thyroid Stimulating Hormone (TSH) is produced by the pituitary gland and acts to increase the functioning of the thyroid gland, This stimulation in turn encourages the production of triiodothyronine (T3) and thyroxine (T4) by the thyroid. Elevated TSH may be indicative of an underactive thyroid, In comparison, reduced TSH may be associated with an overactive thyroid.