What is it?

An Advanced Thyroid Function Profile builds on the basic thyroid check by adding antibody markers and total thyroxine. It typically includes TSH, Free T4, Free T3, Thyroid Peroxidase Antibodies, Thyroglobulin Antibodies, and Total T4. This broader panel helps investigate whether thyroid dysfunction has an autoimmune cause.

Why is it measured?

It is used when a more detailed picture of thyroid health is needed — for example, if basic results are borderline, if there is a family history of autoimmune thyroid disease, or if symptoms persist despite normal initial tests.

What can high results mean?

Positive antibody results suggest the immune system may be targeting the thyroid gland, even if hormone levels are currently normal. Raised hormone levels point towards an overactive thyroid.

What can low results mean?

Low thyroid hormones with raised TSH confirm underactive function. Negative antibody results make an autoimmune cause less likely.

What can affect the result?

• Thyroid medication timing

• Biotin supplements

• Pregnancy and postnatal period

• Recent illness or significant stress

What is follicle stimulating hormone (FSH)

FSH is made by the pituitary gland in the brain. It stimulates the ovaries to grow follicles, which contain eggs, and helps regulate the menstrual cycle.

What a high result might mean

High FSH can mean the ovaries are not responding well, which happens naturally after menopause or earlier in conditions such as premature ovarian insufficiency. It can also rise after some medical treatments affecting the ovaries.

What a low result might mean

Low FSH can occur if the brain is not sending enough signals to the ovaries, often due to stress, significant weight loss, or excessive exercise. Hormonal contraception also lowers FSH levels while in use.

What is the Free Androgen Index (FAI)?

The Free Androgen Index (FAI) is a calculation that estimates how much testosterone in your blood is active. It is worked out by comparing your total testosterone level with the amount bound to a protein called SHBG. This gives an indication of how much hormone is available for your body to use.

What a high result might mean

A high FAI can mean that your body is producing or taking in too much testosterone. It may be linked to anabolic steroid use or, rarely, to hormone-producing growths in the testicles or adrenal glands. In some cases, a low SHBG level can make the FAI appear higher than it really is.

What a low result might mean

A low FAI suggests that the amount of active testosterone may be reduced. This can occur if the testicles are not making enough hormone, or if SHBG levels are high due to age, liver or thyroid problems, or some medicines. Your doctor may repeat the test or calculate your free testosterone for a more accurate picture.

What is luteinising hormone (LH)

LH is made by the pituitary gland in the brain. It helps control the menstrual cycle and triggers ovulation — the release of an egg from the ovary.

What a high result might mean

High LH levels are normal around ovulation or after menopause. In younger women, they can suggest polycystic ovary syndrome or, if both LH and FSH are high, reduced ovarian function.

What a low result might mean

Low LH may mean the brain is not sending enough signals to the ovaries, often due to stress, weight loss, or excessive exercise. Some medicines and hormone treatments can also lower LH levels.

What is oestradiol

Oestradiol is the main form of oestrogen in the body. It is made mainly by the ovaries before menopause and helps control the menstrual cycle, fertility, and bone and heart health.

What a high result might mean

Levels naturally rise around ovulation and in pregnancy. Some medicines or hormone treatments can increase it. Ovarian cysts or, rarely, hormone-producing growths can also raise oestradiol.

What a low result might mean

Low levels are normal after menopause. In younger women, they can happen if the ovaries are not releasing eggs, after major stress, weight loss, or excessive exercise. They can also fall if the pituitary gland is not sending the right signals to the ovaries.

What is prolactin?

Prolactin is a hormone made by the pituitary gland. It helps control breast milk production and affects periods, fertility and sexual function. Levels can rise with stress, sleep and during pregnancy.

What a high result might mean

A raised result is common and often caused by medicines or thyroid or kidney problems. Sometimes it is due to a small growth on the pituitary gland called a prolactinoma. Your doctor will repeat the test, review any medicines, and may arrange a scan if it stays high or if there are symptoms such as headaches or changes in vision.

What a low result might mean

A low level is usually related to treatment with medicines that lower prolactin or to reduced pituitary function. On its own it rarely needs treatment, but your clinician will check other pituitary hormones if needed.

What is sex hormone binding globulin (SHBG)

SHBG is a protein made by the liver that carries hormones such as testosterone and oestrogen through the blood. It controls how much of each hormone is free and active in the body.

What a high result might mean

High SHBG is common during pregnancy, with the pill, or HRT, and in thyroid overactivity. It may also rise with liver conditions or in people who are naturally thin.

What a low result might mean

Low SHBG can be linked with being overweight, insulin resistance, or polycystic ovary syndrome. It means more active hormone is available in the body, which can cause symptoms like acne or unwanted hair growth.

Testosterone

Testosterone is a hormone that helps regulate sex drive, maintain bone strength, control fat distribution, support muscle growth, and stimulate the production of red blood cells and sperm.

In men, most testosterone is produced in the testicles. In women, smaller amounts are made in the ovaries and adrenal glands.

Men’s testosterone levels naturally decline after about age 30, but low levels can occur at any age and may cause symptoms such as reduced libido, erectile dysfunction, tiredness, loss of muscle mass, and low energy.

Although women have much lower testosterone levels than men, testosterone still supports libido, muscle tone, and red blood cell production.

Laboratory reference ranges vary. Guidance from the British Society for Sexual Medicine notes that testosterone may be considered low if it falls below the normal range, or around 12 nmol/L in men who have symptoms suggestive of testosterone deficiency.