Major hormones related to fertility

Emobileclinic Trending Topic: ESTROGEN, PROGESTERONE AND PROLACTIN IN FERTILITY AND INFERTILITY

Understanding the physiology of reproductive hormones, and understanding the pathology can go a long way in your struggle with infertility or maintaining your fertility. Ovaries produce and release two groups of sex hormones—

progesterone and estrogen, while prolactin is released from the pituitary gland. These substances work together to promote the healthy development of female sex characteristics during puberty and to ensure fertility. Estrogen (estradiol, specifically) is instrumental in breast development, fat distribution in the hips, legs, and breasts, and the development of reproductive organs.

Progesterone and Estrogen

Progesterone and estrogen are necessary to prepare the uterus for menstruation, and their release is triggered by the hypothalamus.

These hormones are essential to normal reproductive function—including regulation of the menstrual cycle. As the egg migrates down the fallopian tube after ovulation, progesterone is released. It is secreted by a temporary gland formed within the ovary after ovulation called the corpus luteum. Progesterone prepares the body for pregnancy by causing the uterine lining to thicken. If a woman is not pregnant, the corpus luteum disappears, otherwise, the pregnancy will trigger high levels of estrogen and progesterone, which prevent further eggs from maturing. Progesterone is secreted to prevent uterine contractions that may disturb the growing embryo. The hormone also prepares the breasts for lactation.

Increased estrogen levels near the end of pregnancy alert the pituitary gland to release oxytocin, which causes uterine contractions. Before delivery, the ovaries release relaxin, which as the name suggests, loosens the pelvic ligaments in preparation for labor.

More hormones are released during pregnancy than at any other time of a woman’s life, but during menopause—which marks the end of fertility—estrogen levels fall fast. This can lead to a range of complications. 

There are no indications, other than fertility investigation in females (in some circumstances), which requires progesterone measurement.

Prolactin

In females, prolactin stimulates the breasts to produce milk, after oestrogen priming. During pregnancy, prolactin concentrations begin to increase at approximately six weeks gestation, peaking during late pregnancy.

In males and non-pregnant females, the secretion of prolactin from the pituitary gland is inhibited by the hypothalamic release of dopamine. Tumours or masses that result in compression of the pituitary stalk or drugs that block dopamine receptors, e.g. psychotropics, opiates and dopamine agonists, can cause hyperprolactinemia by reducing dopamine delivery to the pituitary. Hypothyroidism can also be associated with hyperprolactinaemia if levels of thyrotropin-releasing hormone (TRH) are raised, which stimulates prolactin production.

Increased prolactin levels are usually associated with decreased oestrogen or testosterone levels.

Diseases and Disorders Associated With These Hormones 

Hyperprolactinaemia is the most common endocrine disorder of the hypothalamic-pituitary axis and causes infertility in both sexes. Prolactin-secreting tumours (prolactinomas) are the most common type of pituitary tumour. These are usually small tumours (microprolactinomas) and are characterised by anovulation or other menstrual disturbances, galactorrhoea (milk secretion from the breast) and sexual dysfunction. Rarely, tumours may be large (macroprolactinomas) and present with symptoms such as headaches and bitemporal hemianopia (missing vision in the outer halves of the visual field).

N.B. Galactorrhoea can occur in males, but is a much less common symptom of high prolactin in males.

Osteoporosis: Osteoporosis is commonly associated with menopause, just like mood swings and hot flashes. Menopause is marked by the rapid loss of estrogen. The role estrogen play in bone loss can best be described in terms of a battle between osteoclasts (bone absorbing cells) and osteoblasts (bone producing cells). Estrogen is on the side of the osteoblasts, but as the estrogens diminish, the osteoblasts are discouraged from producing more bone. As such, the osteoclasts win by absorbing more bone than is being produced by the osteoblasts.

Estrogen replacement therapy during menopause protects bone mass and helps protect against the risk of osteoporotic fractures.

Polycystic Ovary Syndrome: Polycystic means “many cysts.” The  key characteristics include signs of hyperandrogenism (or elevated androgens) and oligo/amenorrhea, infertility, irregular menstruation, acne, and increased hair growth on the face and body.

PCOS is essentially caused by a hormone imbalance—many of the symptoms are caused by increased production of androgens. These patients usually have high free testosterone levels.

It’s not uncommon for those diagnosed with PCOS to be overweight, insulin resistant, and have type 2 diabetes. Many of the symptoms of PCOS fade with weight loss.

The ovaries have an immensely important role not only in the female reproductive system but in the endocrine system as a whole. The hormones they secrete ensure the proper development of the female body and promote healthy fertility.

When should reproductive hormones be investigated?

There are multiple indications for measuring reproductive hormone levels, however, in a general practice setting, the most common reasons are for investigating primary or secondary amenorrhoea or oligomenorrhoea in females, and some aspects of investigating fertility. Measuring hormone levels in women with typical symptoms of menopause is usually not necessary. 

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