Testosterone and its effect on Male and female fertility

Testosterone is an androgenic sex hormone produced primarily in the testes, however the adrenal glands also secrete small amounts.

It’s considered the most important androgen hormone in men, as it influences spermatogenesis, development of secondary traits and sexual differentiation in the foetal period. However, testosterone is also present in women and has specific functions.

What’s the testosterone?

Testosterone is a sex steroid hormone derived from cholesterol and classified in the group of androgens. It is the main hormone in the testes and is mainly synthesized by Leydig cells although it is also secreted by the adrenal glands.

In women, it is produced in the theca cells of the follicles in small quantities. It’s then converted into estradiol by the action of certain enzymes in granulosa cells, the main female sex hormone.

Testosterone production is regulated by LH (luteinizing hormone), which is secreted by the pituitary when there’re low levels of testosterone.

What is the testosterone function in men?

Testosterone is the most important sex hormone in men. During the first weeks of embryonic development, testosterone, together with the inhibitory substance of the Müllerian ducts, are responsible for male sexual differentiation. The testosterone metabolite, dihydrotestosterone, induces the formation of male external genitalia and the development of secondary sexual characteristics.

Testosterone production increases once puberty is reached and its functions are:

• Growth of external genitals
• Growth of the internal genitals: seminal vesicles, prostate and bulbourethral glands.
• Phenotypic changes: the voice deepens, pubic hair growth with a male pattern and beard appears.
• Increase in muscle and bone mass.
• Mental changes: more aggressive attitude, sexual desire, increased libido …
• Stimulates Sertoli cells for sperm production.
• Influences sperm maturation (spermiogenesis).

What is the testosterone function in women?

In women, testosterone is also important as it is the precursor for the synthesis of estradiol (the main female sex hormone). Testosterone is synthesized in the ovary and adrenal glands and, together with other androgens, play an important role in bone metabolism, sexual desire, and cognitive function.

Adequate follicular development is also regulated by androgens. Elevated levels are observed in patients with polycystic ovary syndrome (PCOS), obtaining abnormal and dysfunctional growth of the antral follicles.

Different studies, androgens have been shown to stimulate the synthesis of FSH receptors, a key hormone in follicular development and selection.

What are the testosterone normal values?

Testosterone levels may vary throughout the day, being higher at night. Measurement of these levels is done through a blood test.

Most of the testosterone (98%) is bound to proteins. These proteins are albumin and sex hormone binding globulin (SHBG). The other fraction called free testosterone, as its name suggests, is not bound to proteins.

It should be noted that a normal range can vary between laboratories and that is why this data must always be interpreted by a professional expert in the field.

The normal plasma concentration of total testosterone is between 300-1000ng / dL in men. And in women, as mentioned above, the levels are lower, the appropriate range being between 30-70ng / dL.

Why testosterone levels may decrease?

Testosterone levels can drop over the years. However, low levels in men can be caused by different causes:

• Trauma, surgery, or infection to the testicles.
• Treatment for testicular cancer with chemotherapy or radiation therapy.
• Pituitary or hypothalamus insufficiency.
• Chronic pathologies: obesity, kidney diseases, liver diseases, HIV.
• Adverse reactions to certain medications such as opiates.
• Genetic diseases: Kallman syndrome, Klinelfelter syndrome, myotonic dystrophy, or Prader-Willi.
• Consumption of anabolics.

In women, testosterone levels may be decreased by:

• Menopause
• Oophorectomy
• Administration of medications: contraceptives or corticosteroids.
• Endocrine diseases
• Hyperprolactinemia
• Pituitary gland disorder: Addison’s disease.

What are the tstosterone low levels consequences?

Symptoms caused by low testosterone levels in men can be:

• low sperm count which leads to fertility problems,
• decreased livid,
• erection problems,
• breast enlargement,
• emotional changes,
• loss of muscle mass and
• hair loss among others.

On the other hand, very low androgen levels in women are associated with

• low ovarian response,
• osteoporosis,
• changes in breast tissue or
• low sexual desire.

Can we artificially administer testosterone?  

After confirmation by clinical data and biochemical tests of the testosterone deficiency, the specialist will suggest the treatment only in cases where it’s necessary and safe.

The exogenous administration of testosterone can be carried out through different presentations:

• Gel: the guidelines on how to proceed with the administration should be followed. Apply to a clean and dry area of ​​intact skin. Once finished it is necessary to wash your hands with soap and water.
• Injections: these must be administered very slowly into the muscle, and the process must be carried out by a doctor or nurse.
• Patches: should be placed on the skin, generally at night and left to act for 24 hours. Follow the instructions on the leaflet.
• Implants: the implant is placed through a small incision in the skin. These slowly release testosterone over a period of 3 to 5 months.

Like any drug, is possible that it generates certain adverse reactions, so it’s important to carry out a medical follow-up.

What do we use testosterone for during in vitro fertilization (IVF) treatment?

Different studies have proposed that androgens have an effect on the initial development of follicles. A high concentration could increase the expression of the FSH receptor and thus improve the follicular response.

The mechanism by which testosterone and dehydroepiandrostene increase androgens is different. Although there are studies in this regard, there’s not much evidence. More recent research has suggested administrating transdermal testosterone prior to ovarian stimulation in patients with low ovarian reserve.Paragraph

The correct use of this treatment could mean a greater number of oocytes after follicular puncture, a lower rate of cancellation and a higher rate of clinical pregnancy. These data remain controversial and further studies are needed to confirm them. Therefore, the administration of testosterone should be prescribed by a specialist after an exhaustive study of the patient’s medical history.

Laura Martí, a biologist at Instituto Bernabeu.