By Dr. Alison McAllister, ZRT Laboratory
If you are experiencing infertility issues, this article is for you. The purpose is to explain what hormones are tested in a fertility profile and why each one is important. Our Fertility Test (Saliva & Blood Spot) measures all of the key reproductive hormones discussed below from a simple at-home collection.
Pituitary Hormones: LH and FSH
LH and FSH are pituitary hormones whose communication with growing egg follicles in the ovaries is one of the only positive feedback loops in the body. On day three or four of the menstrual cycle (day one is the first day of the period), LH and FSH are at their lowest level. This relationship is normally a 1:1 function, but some women have LH levels that are two or three times greater than their FSH levels on day three or four of their cycle — a sign of polycystic ovarian syndrome (PCOS), occurring in approximately 50% of PCOS women.
Think of FSH and LH as calling out to the ovaries. Lower levels suggest the brain is barely whispering to call for an egg and its estrogen. Higher levels (fourteen and above) suggest the brain is shouting for eggs and estrogen — reflecting that the number of eggs is decreasing. This is one of the most important tests in the fertility profile because high levels suggest that immediate assistance from a fertility specialist should be sought.
Sex Hormones
The fertility profile measures sex hormones at the mid-luteal peak, which occurs seven days after ovulation. For many women, this is generally day 21 of the cycle, but it will fall on a different day in women with shorter or longer cycles.
Estradiol
Estradiol is one of three types of estrogen and the primary estrogen measured in the fertility profile. Estrogens help to develop the uterine lining and are important for breast development. Inadequate estrogen can be a sign of lack of ovulation or low ovarian health and can impede healthy implantation of the developing embryo.
Progesterone
Progesterone is produced from the corpus luteum after ovulation and creates an optimally functioning uterine lining. Lower levels suggest ovulation is not occurring, an inadequate corpus luteum is being produced, or that the corpus luteum is failing before implantation occurs. Estrogen helps to build tissue and progesterone develops the tissue to accept a fertilised egg.
Testosterone
Testosterone is produced from the ovaries and turns into estradiol within the ovaries — a sign of healthy ovulation. When testosterone levels are too high, as seen in women with PCOS, the follicles and egg quality are poor. High testosterone also interferes with ovulation, which can cause cycles to become irregular. High testosterone is partially stimulated by high insulin levels.
Adrenal Hormones
DHEA-S
DHEA-S is one of the primary hormones in the body and serves as a precursor to testosterone and estradiol. Low levels of DHEA-S can lead to lower estrogen levels and changes in the immune system. High levels of DHEA-S are often associated with higher insulin levels, higher testosterone levels and PCOS.
Cortisol
Cortisol is a primary adrenal hormone produced in response to stress — and like all hormones, balance is critical. Low levels of cortisol prevent optimal thyroid function at the cellular receptors, but high levels can inhibit thyroid function and ovulation. The old saying “Relax and you’ll get pregnant” comes from the role that cortisol plays in balancing ovulation. Balanced cortisol levels are important for ovulation and pregnancy.
Thyroid Hormones
Thyroid function is one of the most commonly missed factors in fertility investigations. Our Thyroid & Iodine Test Kit measures TSH, Free T4, Free T3, TPO antibodies and urinary iodine — covering the full thyroid and iodine picture that is so often overlooked in standard fertility workups.
TSH (Thyroid Stimulating Hormone)
TSH is produced in the brain’s pituitary gland and signals to the thyroid gland the need to make thyroid hormone. High TSH means there is low thyroid production; low TSH means there is high thyroid production. For fertility health, a good TSH range is generally accepted as less than 2.5. Levels of TSH greater than 2.5 are associated with poorer pregnancy and ovulation rates.
Free T4 and Free T3
Free T4 and Free T3 are the two hormones made by the thyroid gland. They are called “free” because they are not bound to thyroid binding globulin (TBG). Free T4 and Free T3 levels reveal how effective the thyroid gland is at responding to TSH stimulation.
Thyroid Peroxidase Antibody (TPOab)
TPOab is a cross-reactivity antibody created by an immune reaction that mistakenly targets the thyroid gland. Thyroid autoimmunity is the most common cause of hypothyroidism. TPOab is a sign that other immune reactions are happening — commonly gastrointestinal parasites or food reactions. Coeliac disease is commonly found in women with TPO, and individuals with coeliac disease have a higher percentage of infertility until treated with a gluten-free diet. Thyroid autoimmunity also contributes to a much higher rate of miscarriages in the first trimester.
Vitamin D3
Vitamin D3 is converted in the body to a hormone that is in the same family as estradiol and thyroid. It is very important in opening receptors in the cells. Vitamin D3 deficiency is extremely common, even in sunny climates. Restoration to satisfactory levels has been found to improve fertility rates in PCOS women and women doing IVF treatments. Vitamin D3 is also important in the immune system and in regulating insulin levels.
Our Vitamin D Test (D2, D3 and Total) measures your complete vitamin D status from a simple finger-prick at home — highly recommended for any woman investigating fertility, especially those with PCOS or a history of miscarriage.
Originally by Dr. Alison McAllister, ZRT Laboratory. Reproduced with permission. Last reviewed: May 2026.