Follicle-stimulating hormone (FSH) is produced by pituitary gland and plays a key role in the reproductive system of both men and women. In women, FSH regulates the growth of ovarian follicles which secrete progesterone and Estrogen that are required for key events during the menstrual cycle. In men, FSH plays a key role in the development of the testes as well as the production of sperm.

Luteinizing hormone (LH) is produced in the anterior pituitary gland and plays an important role in regulating the function of the reproductive tissues which include the ovaries in females and testes in males.

In women, during the first half of a typical menstrual cycle (roughly weeks one to two), LH is required to stimulate the ovarian follicles that are located in the ovaries to produce the female sex hormone oestradiol. LH naturally rises at around day 14 of a women’s cycle and this surge is vital in stimulating the ovaries to release an egg during ovulation. Given fertilization occurs, LH also stimulates the corpus luteum, which secretes progesterone that is essential for sustaining pregnancy.

For men, LH plays a key role in stimulating the production of the main male sex hormone (testosterone) from Leydig cells present in the testes. Further to this, testosterone is then able to stimulate the production of sperm as well as contribute to the development of a set of characteristic traits which range from increased muscle and bone mass to the degree of bodily hair present.

LH also stimulates the production of testosterone in females. Consistently raised LH in women is often associated with polycystic ovary syndrome in which excessive amounts of testosterone are produced as a result of elevated LH. In contrast, low levels of LH may result in the halt of ovulation.

Low levels of LH may be a cause of infertility in both men and women due to levels being insufficient in stimulating sperm production or the ovulation process.

Testosterone is a male sex hormone that is produced in the testicles of men and to a lesser extent in the ovaries of women. In men, testosterone plays an important role in the development of the male reproductive tissues including the prostate and testes. Testosterone is responsible for a variety of traits which can range from; increasing the mass of bone and muscle to influencing the growth of hair on the body. Therefore, men with lower levels of testosterone may encounter a reduction in these traits, whilst women with raised testosterone may encounter an increase in these traits. Raised testosterone is commonly observed in women with polycystic ovaries syndrome in which increased body hair, acne or a deepened voice may be characteristic.

The Free Androgen Index (FAI) is a ratio used to determine the amount of free androgen hormones within the blood and whether this is within the normal range. Testosterone readily binds to proteins within the blood such as SHBG, though it can also be found in a free, unbound state. The FAI ratio is based on measurements of testosterone present in your blood in comparison to the total amount of testosterone plus SHBG in your body. In women, an elevated value for FAI could indicate polycystic ovary syndrome. In men, a low value could be indicative of a reduced availability of testosterone which may be associated to symptoms including loss of muscle mass, libido and erectile dysfunction.

Oestradiol is an important steroid hormone that can be found in both men and women. In women, oestradiol is mainly produced by the ovaries and plays a key role in the maturation and maintenance of the female reproductive system.

In comparison, men produce considerably lower amounts of oestradiol. This is mainly produced by the testes where some testosterone is converted into oestradiol which is a vital component for the production of sperm. Oestradiol may also be produced to lesser extent by fat tissue in both men and women. Elevated levels of oestradiol may lead to a host of conditions ranging from depression to acne. A raised result has also been found to be associated with an increased risk of breast and uterine cancer. In contrast, low levels may affect the menstrual cycle, fertility, mental health or even lead to osteoporosis. In men, increased oestradiol can lead to infertility, loss of libido or the development of breast tissue. Levels may rise due to the accumulation of excessive fat tissue that secretes oestradiol.

Prolactin is a hormone which is produced in the pituitary gland in both men and women. Prolactin can also influence the levels of other important hormones such as Estrogen and testosterone in both sexes. In women, prolactin stimulates the production of milk following the birth of a child. Consequently, levels are characteristically high in pregnant and breastfeeding women. However, elevated prolactin levels in both men and women that are not pregnant or breastfeeding is a condition known as hyperprolactinemia and may lead to loss of libido, bone density loss and potential infertility. In women in particular, elevated prolactin may also lead to other issues such as vaginal dryness or disruptions to the normal menstrual cycle subsequently leading to irregular periods. In comparison, symptoms specific to men in response to high levels of prolactin may include breast enlargement or erectile dysfunction.

SHBG is a protein that is produced by your liver and is able to bind tightly with three main sex hormones (dihydrotestosterone (DHT), testosterone and Estrogen). These hormones can be found in your blood in an unbound, free form in both women and men. However, when SHBG binds to them they become bound and unavailable to the cells of your body, therefore, SHBG can influence the amount of these free hormones that is available to your tissues. A high value for SHBG can indicate a lack of testosterone or oestrogen available to your tissues whilst a low SHBG value can indicate an excess amount of these hormones available. Causes for changes in the level of SHBG other than sex and age include hyperthyroidism and liver disease.

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.

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.