Testosterone

Testosterone testing is commonly done to check the reproductive potential in both men and women. It is the key sexual hormone in men. Testosterone is an androgen, which means that it is responsible for the development of the male characteristics in any individual. Besides regulating fertility, it is responsible for the development of muscle mass, fat distribution, bone growth, as well as production of red blood cells.

Upto 98% of the testosterone in your body, circulates in the bloodstream bound to proteins. Free testosterone is only less than 4%. Total testosterone measured by the laboratories is sum of the two.

Testosterone in men is produced mainly by the Leydig cells in testes. It responsible for the sexual development of boys in adolescence and sperm development, libido, and other sexual functions later in adulthood.

Testosterone in women is produced in the ovaries, although it is present in much smaller quantities as compared to the men. Majority of the testosterone produced in the ovaries is converted to estrogen. Nevertheless, an adequate balance of estrogen-testosterone is required and together they help with the growth and maintenance of a woman’s reproductive system, bone mass, and even emotional behaviors.

Small amounts of this hormone are also produced by the adrenal glands in both men and women.

What is the use of Testosterone?

Testosterone test in men is often used along with other hormone tests to evaluate the reason for:

• Early or delayed puberty in boys
• Infertility
• Reduced sex drive
• Erectile dysfunction
• Testicular tumors

In women, testosterone test is used to check:

• The reason for infertility
• Lowered sex drive
• PCOS and development of masculine traits such as excessive facial and body hair (hirsutism)
• Oily skin and sudden appearance of acne on the face

In infants, testosterone test is used when:

• Genitals are not clearly male or female

Testosterone testing is also done in cases of Hypothalamus or pituitary disorders in both men and women. Additionally, it is used in transgender individuals when they are undergoing hormone therapy.

When should you do the Testosterone test?

The testosterone test is ordered in one or more of the below situations:

• Infertility: Conception problems and infertility in both men and women may be due to hormonal problems
• Reduced sex drive: If your sex drive is lower than usual
• Erectile dysfunction in men: If you’re facing erectile problems
• Lack of body/facial hair: If you see your facial hair thinning and are losing body hair, it may be due to hormonal imbalance
• Small testicles: Very small, inadequately grown testicles even after pubertal age
• Inadequate muscle mass: If your muscles are not growing as they should
• Gynecomastia in men: Female characteristics can develop as the male characteristics are suppressed in the absence of enough testosterone
• Precocious or delayed puberty: Puberty in boys is expected to appear between 9 and 14 years, and if the signs of puberty appear early or later than the expected age, testosterone may be tested. The common signs of puberty in boys are:
  • Growth of testicles and penis
  • Facial hair
  • Pubic hair and heavier body hair
  • Heavier voice
  • Growth of muscles
• Irregular or missing periods in women: Menstruation works on a proper balance of hormones in the human body and when that is disrupted, you may have period problems or PCOS
• Masculine feature in women: Male pattern baldness, appearance of facial hair and body hair (hirsutism) in women could be due to excessive testosterone
• Improper genitals in infants: If genitals are not properly defined in infants, hormone testing is done to confirm if they are transgender babies

How is this hormone regulated?

Hypothalamus in your brain first releases the gonadotrophin-releasing hormone (GnRH), which stimulates the pituitary to release luteinizing hormone, which in turn stimulates the testes in men and ovaries in women to produce and release testosterone into the bloodstream.

As the level of blood testosterone rises, the hypothalamus is again triggered via the negative-loop, signaling it to suppress the production of GnRH, hence halting the cycle until the hormone levels in the bloodstream fall and the hypothalamus is activated again to resume the whole cycle.

What are the normal testosterone levels by age?

Testosterone in males usually peaks at around the age of 20 years and gradually declines with age. After 30 years, it is expected that the total testosterone in men may decrease 1% per year.

As a result of this drop, some men feel significant changes in their body—low physical energy, strength, stamina, weight gain, reduced mental acuity—while others don’t feel anything. This is more apparent after the age of 60, and is referred to as hypogonadism, andropause or ‘male menopause.’

What is the ideal level of testosterone before IVF?

The normal levels of testosterone vary from person to person, depending upon a few factors such as the thyroid function. As long as your testosterone is in the normal range, it will be considered acceptable for IVF.

Guidelines from the American Urological Association (AUA) suggest that testosterone levels above 300ng/ml are normal. If your testosterone is below 300 ng/dl, more investigations may be ordered.

Normal testosterone levels in women are usually between 8 and 60 ng/dl.

Testosterone levels tend to decline after the age of 20 years and if a woman has testosterone deficiency while she’s pregnant with, it may adversely affect the development of a male baby.

What are the causes of low testosterone?

Low testosterone levels in men can just be due to ageing but they could also be due to:

• An injury or infection of the testes
• Viral diseases like mumps
• Chemo or radiation therapy in cancer patients
• HIV infection
• Chronic liver and kidney diseases
• Type 2 diabetes
• Autoimmune diseases
• Inflammatory conditions such as sarcoidosis
• Alcohol abuse
• Hypothalamic or pituitary disease
• Long term use of certain medications such as antidepressants, narcotics, opioids, steroids
• Genetic diseases such as Klinefelter, Kallman, or Prader-Willi syndromes that cause reduced production of this hormone, or muscular dystrophy
• Delayed puberty
• Extremely high levels of stress

Low testosterone levels in women can be due to:

• Ovarian failure
• Long-term use of birth-control or other medications
• Diseases of the pituitary or hypothalamus

What is the reason for high testosterone?

Increased levels of testosterone in men can be due to:

• Use of anabolic steroids
• Adrenal tumors
• Tumors of the testes
• Precocious puberty
• Congenital adrenal hyperplasia
• Testosterone supplements and gels

Causes of high testosterone in women can be due to:

• Polycystic ovary syndrome (PCOS)
• Tumors of the ovaries or adrenal gland
• Steroid abuse
• Congenital adrenal hyperplasia

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Thomas G. Travison, Hubert W. Vesper, Eric Orwoll, Frederick Wu, Jean Marc Kaufman, Ying Wang, Bruno Lapauw, Tom Fiers, Alvin M. Matsumoto, Shalender Bhasin, Harmonized Reference Ranges for Circulating Testosterone Levels in Men of Four Cohort Studies in the United States and Europe, The Journal of Clinical Endocrinology & Metabolism, Volume 102, Issue 4, 1 April 2017, Pages 1161–1173, https://doi.org/10.1210/jc.2016-2935

Mulhall JP, Trost LW, Brannigan RE et al: Evaluation and management of testosterone deficiency: AUA guideline. J Urol 2018; 200:423. https://www.auanet.org/guidelines/guidelines/testosterone-deficiency-guideline

University of Rochester Medical Center, Total Testosterone https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=testosterone_total