Hypogonadism
Encyclopedia
Hypogonadism is a medical term for decreased functional activity of the gonad
Gonad
The gonad is the organ that makes gametes. The gonads in males are the testes and the gonads in females are the ovaries. The product, gametes, are haploid germ cells. For example, spermatozoon and egg cells are gametes...

s. Low testosterone is caused by a decline or deficiency in gonadal production of testosterone in males. The gonads, typically called testicles in males, produce hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

s (testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

, estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...

, antimullerian hormone, progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...

, inhibin B, activin) and gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...

s or sperm
Spermatozoon
A spermatozoon is a motile sperm cell, or moving form of the haploid cell that is the male gamete. A spermatozoon joins an ovum to form a zygote...

.

In men

Effects of low testosterone in men may include: (not all are present in any single individual)
  • Poor libido
    Libido
    Libido refers to a person's sex drive or desire for sexual activity. The desire for sex is an aspect of a person's sexuality, but varies enormously from one person to another, and it also varies depending on circumstances at a particular time. A person who has extremely frequent or a suddenly...

     (Low sexual desire)
  • Fatigue (medical) always tired
  • Muscle loss/atrophy
    Atrophy
    Atrophy is the partial or complete wasting away of a part of the body. Causes of atrophy include mutations , poor nourishment, poor circulation, loss of hormonal support, loss of nerve supply to the target organ, disuse or lack of exercise or disease intrinsic to the tissue itself...

  • Erectile Dysfunction
    Erectile dysfunction
    Erectile dysfunction is sexual dysfunction characterized by the inability to develop or maintain an erection of the penis during sexual performance....

  • Increasing abdominal fat
  • Glucose
    Glucose
    Glucose is a simple sugar and an important carbohydrate in biology. Cells use it as the primary source of energy and a metabolic intermediate...

     intolerance (early diabetes)
  • High Cholesterol/Lipid
    Lipid
    Lipids constitute a broad group of naturally occurring molecules that include fats, waxes, sterols, fat-soluble vitamins , monoglycerides, diglycerides, triglycerides, phospholipids, and others...

  • Poor sleep
  • Difficulty concentrating
  • Memory Loss
    Memory loss
    Memory loss can be partial or total and it is normal when it comes with aging. Sudden memory loss is usually a result of brain trauma and it may be permanent or temporary. When it is caused by medical conditions such as Alzheimers, the memory loss is gradual and tends to be permanent.Brain trauma...

    -difficulty in choosing words in language
  • Shyness
    Shyness
    In humans, shyness is a social psychology term used to describe the feeling of apprehension, lack of comfort, or awkwardness experienced when a person is in proximity to, approaching, or being approached by other people, especially in new situations or with unfamiliar people...

  • Depression
    Depression (mood)
    Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...

  • Anxiety
    Anxiety
    Anxiety is a psychological and physiological state characterized by somatic, emotional, cognitive, and behavioral components. The root meaning of the word anxiety is 'to vex or trouble'; in either presence or absence of psychological stress, anxiety can create feelings of fear, worry, uneasiness,...

  • Psychological and relationship problems
  • Gynecomastia
    Gynecomastia
    Gynecomastia or Gynaecomastia, , is the abnormal development of large mammary glands in males resulting in breast enlargement. The term comes from the Greek γυνή gyné meaning "woman" and μαστός mastós meaning "breast"...

  • Hot flashes
  • Decrease in growth of, or loss of, beard and body hair
  • Loss of bone
    Bone
    Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

     mass (osteoporosis
    Osteoporosis
    Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...

    )
  • Irritability
  • Infertility
    Infertility
    Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...

  • Shrinking of the testicles
  • Decrease in firmness of testicles
  • Frequent urination (polyuria
    Polyuria
    Polyuria is a condition usually defined as excessive or abnormally large production or passage of urine . Frequent urination is sometimes included by definition, but is nonetheless usually an accompanying symptom...

    ) without infection; waking at night to urinate ([nocturia])
  • Achy muscles
  • Liquid stools
  • Night sweats
  • Dry skin and/or cracking nails
  • Reduced Quality of Life

In women

Effects of low estrogen levels in women may include: (not all are present in any individual)
  • Hot flashes
  • Poor libido
    Libido
    Libido refers to a person's sex drive or desire for sexual activity. The desire for sex is an aspect of a person's sexuality, but varies enormously from one person to another, and it also varies depending on circumstances at a particular time. A person who has extremely frequent or a suddenly...

  • Infertility
  • Loss of, or failure to develop, menstruation
    Menstruation
    Menstruation is the shedding of the uterine lining . It occurs on a regular basis in sexually reproductive-age females of certain mammal species. This article focuses on human menstruation.-Overview:...

  • Loss of body hair
  • Loss of bone
    Bone
    Bones are rigid organs that constitute part of the endoskeleton of vertebrates. They support, and protect the various organs of the body, produce red and white blood cells and store minerals. Bone tissue is a type of dense connective tissue...

     mass (osteoporosis
    Osteoporosis
    Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...

    )
  • Heart disease
  • Sleep disturbances
  • Symptoms of urinary bladder discomfort like frequency, urgency, frequent infections, lack of lubrication, discharge
  • Shrinking of breasts
  • Loss of or nonexistent sense of smell

In men

Low Testosterone
Testosterone
Testosterone is a steroid hormone from the androgen group and is found in mammals, reptiles, birds, and other vertebrates. In mammals, testosterone is primarily secreted in the testes of males and the ovaries of females, although small amounts are also secreted by the adrenal glands...

 can be identified through a simple blood test performed by a laboratory, ordered by a physician. This test is typically ordered in the morning hours, when levels are highest, as levels can drop by as much as 13% during the day.

Normal total testosterone levels range from 300 - 1000 ng/dL

Treatment is often prescribed for total testosterone levels below 350 ng/dL. If the serum total testosterone level is between 230 and 350 ng/dL, repeating the measurement of total testosterone with sex hormone-binding globulin (SHBG) to calculate free testosterone or free testosterone by equilibrium dialysis may be helpful.

Treatment may be necessary even if the patient's total testosterone level is within the "normal" range. The standard range given is based off widely varying ages and, given that testosterone levels naturally decrease as humans age, age-group specific averages should be taken into consideration when discussing treatment between doctor and patient. A twenty-seven year old male with a testosterone level of 380ng/dL would be in the "normal" range, but would likely have low testosterone to blame if he experiences some or many of the above symptoms. This score would put him in the bottom 5% of his age-group, but would be a more common score for a man who is 80+ years old.

Blood testing
A position statement by The Endocrine Society has expressed dissatisfaction with the manner in which most assays for TT (Total Testosterone) and FT (Free Testosterone) are currently performed. In particular, research has questioned the validity of commonly administered assays of FT by RIA. The FAI (Free Androgen Index) has been found to be the worst predictor of Free Testosterone.

In women

Similar to men, the LH
Luteinizing hormone
Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...

 and FSH
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...

 will be used, particularly in women who believe they are in menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...

. These levels change during a woman's normal menstrual cycle, so the history of having ceased menstruation coupled with high levels aids the diagnosis of being menopausal. Commonly, the post-menopausal woman is not called hypogonadal if she is of typical menopausal age. Contrast with a young woman or teen, who would have hypogonadism rather than menopause. This is because hypogonadism is an abnormality, whereas menopause is a normal change in hormone levels.

Hypogonadism is often discovered during evaluation of delayed puberty
Delayed puberty
Puberty is described as delayed puberty with exceptions when an organism has passed the usual age of onset of puberty with no physical or hormonal signs that it is beginning. Puberty may be delayed for several years and still occur normally, in which case it is considered constitutional delay, a...

, but ordinary delay, which eventually results in normal pubertal
Puberty
Puberty is the process of physical changes by which a child's body matures into an adult body capable of reproduction, as initiated by hormonal signals from the brain to the gonads; the ovaries in a girl, the testes in a boy...

 development, wherein reproductive function is termed constitutional delay. It may be discovered during an infertility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...

 evaluation in either men or women.

Treatment

Male hypogonadism is most often treated with testosterone replacement therapy
Androgen replacement therapy
Androgen replacement therapy is a hormone treatment often prescribed to counter the effects of male Hypogonadism. It is also prescribed to lessen the effects or delay the onset of normal male aging...

 (TRT) in patients who are not trying to conceive. Commonly-used testosterone replacement therapies include transdermal
Transdermal
Transdermal is a route of administration wherein active ingredients are delivered across the skin for systemic distribution. Examples include transdermal patches used for medicine delivery, and transdermal implants used for medical or aesthetic purposes....

 (through the skin) using a patch or gel, injections, or pellets. Oral testosterone is no longer used in the U.S. because it is broken down in the liver and rendered inactive; it also can cause severe liver damage. Like many hormonal therapies, changes take place over time. It may take as long as 2–3 months at optimum level to reduce the symptoms, particularly the wordfinding and cognitive dysfunction. Testosterone levels in the blood should be evaluated to ensure the increase is adequate. Levels between 500 and 700 ng/dL are considered adequate for young, healthy men from 20 to 40 years of age, but the lower edge of the normal range is poorly defined and single testosterone levels alone cannot be used to make the diagnosis. Modern treatment may start with 200 mg intramuscular testosterone, repeated every 10–14 days. Getting a blood level of testosterone on the 13th day will give a "trough" level, assisting the physician in deciding whether the correct dose is being given.

Recently some have reported using anastrozole
Anastrozole
Anastrozole is an aromatase-inhibiting drug approved for treatment of breast cancer after surgery, as well as for metastasis in both pre and post-menopausal women. The severity of breast cancer is increased by estrogen, as sex hormones cause hyperplasia, and differentiation at estrogen receptor...

 (Arimidex), an aromatase inhibitor used in women for breast cancer, to decrease conversion of testosterone to estrogen in men, and increase serum testosterone levels.

While historically men with prostate cancer risk were warned against testosterone therapy, that has shown to be a myth.

Other side effects can include an elevation of the hematocrit to levels that require blood to be withdrawn (phlebotomy
Phlebotomist
Phlebotomists are individuals trained to draw blood from a live person or animal.Phlebotomists collect blood primarily by performing venipuncture and, for collection of minute quantities of blood, fingersticks. Blood may be collected from infants by means of a heel stick...

) to prevent complications from it being "too thick". Another is that a man may have some growth in the size of the breasts (gynecomastia), though this is relatively rare. Finally, some physicians worry that Obstructive Sleep Apnea may worsen with testosterone therapy, and should be monitored.

Another feasible treatment alternative is human chorionic gonadotropin
Human chorionic gonadotropin
Human chorionic gonadotropin or human chorionic gonadotrophin is a glycoprotein hormone produced during pregnancy that is made by the developing embryo after conception and later by the syncytiotrophoblast .. Some tumors make this hormone; measured elevated levels when the patient is not...

 (hCG).

For both men and women, an alternative to testosterone replacement is Clomifene
Clomifene
Clomifene or clomiphene or Clomid or Clomifert is a selective estrogen receptor modulator that increases production of gonadotropins by inhibiting negative feedback on the hypothalamus...

 treatment which can stimulate the body to naturally increase hormone levels while avoiding infertility and other side effects as a consequence of direct hormone replacement therapy.

For women, estradiol
Estradiol
Estradiol is a sex hormone. Estradiol is abbreviated E2 as it has 2 hydroxyl groups in its molecular structure. Estrone has 1 and estriol has 3 . Estradiol is about 10 times as potent as estrone and about 80 times as potent as estriol in its estrogenic effect...

 and progesterone
Progesterone
Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...

 are replaced. Some types of fertility defects can be treated, others cannot. Some physicians will also give testosterone to women, mainly to increase libido.

Classification

Deficiency of sex hormones can result in defective primary or secondary sexual development, or withdrawal effects (e.g., premature menopause
Menopause
Menopause is a term used to describe the permanent cessation of the primary functions of the human ovaries: the ripening and release of ova and the release of hormones that cause both the creation of the uterine lining and the subsequent shedding of the uterine lining...

) in adults. Defective egg or sperm development results in infertility
Infertility
Infertility primarily refers to the biological inability of a person to contribute to conception. Infertility may also refer to the state of a woman who is unable to carry a pregnancy to full term...

. The term hypogonadism is usually applied to permanent rather than transient or reversible defects, and usually implies deficiency of reproductive hormones, with or without fertility
Fertility
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

 defects. The term is less commonly used for infertility without hormone deficiency. There are many possible types of hypogonadism and several ways to categorize them. Hypogonadism is also categorized by endocrinologists by the level of the reproductive system that is defective.Physicians measure gonadotropin
Gonadotropin
Gonadotropins are protein hormones secreted by gonadotrope cells of the pituitary gland of vertebrates. This is a family of proteins, which include the mammalian hormones follitropin , lutropin , placental chorionic gonadotropins hCG and eCG and chorionic gonadotropin , as well as at least two...

s (LH
Luteinizing hormone
Luteinizing hormone is a hormone produced by the anterior pituitary gland. In females, an acute rise of LH called the LH surge triggers ovulation and development of the corpus luteum. In males, where LH had also been called interstitial cell-stimulating hormone , it stimulates Leydig cell...

 and FSH
Follicle-stimulating hormone
Follicle-stimulating hormone is a hormone found in humans and other animals. It is synthesized and secreted by gonadotrophs of the anterior pituitary gland. FSH regulates the development, growth, pubertal maturation, and reproductive processes of the body. FSH and Luteinizing hormone act...

) to distinguish primary from secondary hypogonadism. In primary hypogonadism the LH and/or FSH are usually elevated, meaning the problem is in the testicles, whereas in secondary hypogonadism, both are normal or low, suggesting the problem is in the brain.

Affected system

  • Hypogonadism resulting from defects of the gonads is traditionally referred to as primary hypogonadism. Examples include Klinefelter syndrome and Turner syndrome
    Turner syndrome
    Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

    . Mumps
    Mumps
    Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...

     is known to cause testicular failure, and in recent years has been immunized against in the US. A varicocele
    Varicocele
    Varicocele , also known as varicoscele or varicose seal, is an abnormal enlargement of the vein that is in the scrotum draining the testicles. The testicular blood vessels originate in the abdomen and course down through the inguinal canal as part of the spermatic cord on their way to the testis...

     can reduce hormonal production as well.

  • Hypogonadism resulting from hypothalamic or pituitary defects are termed secondary hypogonadism or central hypogonadism (referring to the central nervous system
    Central nervous system
    The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

    ).
    • Examples of Hypothalamic
      Hypothalamus
      The Hypothalamus is a portion of the brain that contains a number of small nuclei with a variety of functions...

       defects include Kallmann syndrome
      Kallmann syndrome
      Kallmann syndrome is a genetic disorder marked by anosmia and hypogonadism - the decreased functioning of the glands that produce sex hormones. Abnormalities in various genes may cause a defect in the hypothalamus, causing a deficiency of gonadotropin-releasing hormone ; this in turn causes...

      .
    • Examples of Pituitary
      Pituitary gland
      In vertebrate anatomy the pituitary gland, or hypophysis, is an endocrine gland about the size of a pea and weighing 0.5 g , in humans. It is a protrusion off the bottom of the hypothalamus at the base of the brain, and rests in a small, bony cavity covered by a dural fold...

       defects include hypopituitarism
      Hypopituitarism
      Hypopituitarism is the decreased secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain...

      .

  • An example of a hypogonadism resulting from the lack of hormone response is androgen insensitivity syndrome
    Androgen insensitivity syndrome
    Androgen insensitivity syndrome is a condition that results in the partial or complete inability of the cell to respond to androgens. The unresponsiveness of the cell to the presence of androgenic hormones can impair or prevent the masculinization of male genitalia in the developing fetus, as...

    , where there are inadequate receptors to bind the testosterone, resulting in a female appearance despite XY chromosomes.

Primary or secondary

  • Primary - defect is inherent within the gonad: eg. Noonan syndrome
    Noonan syndrome
    Noonan Syndrome is a relatively common autosomal dominant congenital disorder considered to be a type of dwarfism, that affects both males and females equally. It used to be referred to as the male version of Turner's syndrome ; however, the genetic causes of Noonan syndrome and Turner syndrome...

    , Turner syndrome
    Turner syndrome
    Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

     (45X,0), Klinefelter syndrome (47XXY), XY females with SRY gene-immunity
  • Secondary - defect lies outside of the gonad: eg. Kallmann syndrome
    Kallmann syndrome
    Kallmann syndrome is a genetic disorder marked by anosmia and hypogonadism - the decreased functioning of the glands that produce sex hormones. Abnormalities in various genes may cause a defect in the hypothalamus, causing a deficiency of gonadotropin-releasing hormone ; this in turn causes...

     and Polycystic ovary syndrome
    Polycystic ovary syndrome
    Polycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....

    , also called hypogonadotropic hypogonadism. Hemochromatosis and diabetes mellitus can be causes of this as well.

Congenital vs. acquired

  • Examples of congenital causes of hypogonadism, that is, causes that are present at birth:
    • Turner syndrome
      Turner syndrome
      Turner syndrome or Ullrich-Turner syndrome encompasses several conditions in human females, of which monosomy X is most common. It is a chromosomal abnormality in which all or part of one of the sex chromosomes is absent...

       in females, and Klinefelter syndrome in males. It is also one of the signs of CHARGE
      CHARGE syndrome
      CHARGE syndrome , is a syndrome caused by a genetic disorder. It was first described in 1979.In 1981, the term "CHARGE" came into use as an acronym for the set of unusual congenital features seen in a number of newborn children...

       syndrome.

  • Examples of acquired causes of hypogonadism:
    • Anabolic Steroids
      Anabolic steroid
      Anabolic steroids, technically known as anabolic-androgen steroids or colloquially simply as "steroids", are drugs that mimic the effects of testosterone and dihydrotestosterone in the body. They increase protein synthesis within cells, which results in the buildup of cellular tissue ,...

       Induced Hypogonadism (ASIH)
    • The use of androgen inhibitors such as Finasteride
      Finasteride
      Finasteride is a synthetic antiandrogen that inhibits type II 5-alpha reductase, the enzyme that converts testosterone to dihydrotestosterone...

    • Childhood mumps
      Mumps
      Mumps is a viral disease of the human species, caused by the mumps virus. Before the development of vaccination and the introduction of a vaccine, it was a common childhood disease worldwide...

    • Children born to mothers who had ingested the endocrine disruptor diethylstilbestrol
      Diethylstilbestrol
      Diethylstilbestrol is a synthetic nonsteroidal estrogen that was first synthesized in 1938. Human exposure to DES occurred through diverse sources, such as dietary ingestion from supplemented cattle feed and medical treatment for certain conditions, including breast and prostate cancers...

       for potential miscarriage
    • Traumatic brain injury
      Traumatic brain injury
      Traumatic brain injury , also known as intracranial injury, occurs when an external force traumatically injures the brain. TBI can be classified based on severity, mechanism , or other features...

      , even in childhood.
    • In males, normal aging causes a decrease in androgens, which is sometimes called "male menopause" (also known by the coinage "manopause"), Late-Onset Hypogonadism (LOH), Andropause or Androgen Decline in the Aging Male (ADAM).

Hormones vs. fertility

Hypogonadism can involve just hormone
Hormone
A hormone is a chemical released by a cell or a gland in one part of the body that sends out messages that affect cells in other parts of the organism. Only a small amount of hormone is required to alter cell metabolism. In essence, it is a chemical messenger that transports a signal from one...

 production or just fertility
Fertility
Fertility is the natural capability of producing offsprings. As a measure, "fertility rate" is the number of children born per couple, person or population. Fertility differs from fecundity, which is defined as the potential for reproduction...

, but most commonly involves both.
  • Examples of hypogonadism that affect hormone production more than fertility are hypopituitarism
    Hypopituitarism
    Hypopituitarism is the decreased secretion of one or more of the eight hormones normally produced by the pituitary gland at the base of the brain...

     and Kallmann syndrome
    Kallmann syndrome
    Kallmann syndrome is a genetic disorder marked by anosmia and hypogonadism - the decreased functioning of the glands that produce sex hormones. Abnormalities in various genes may cause a defect in the hypothalamus, causing a deficiency of gonadotropin-releasing hormone ; this in turn causes...

    ; in both cases, fertility is reduced until hormones are replaced but can be achieved solely with hormone replacement.
  • Examples of hypogonadism that affect fertility more than hormone production are Klinefelter syndrome and Kartagener syndrome.

Testosterone and longevity

A longitudinal (18 year) study published by The Endocrine Society
The Endocrine Society
The Endocrine Society is a professional, international medical organization in the field of endocrinology and metabolism, founded in 1916 as The Association for the Study of Internal Secretions. The official name of the organization was changed to The Endocrine Society on January 1, 1952. It is a...

and funded by the National Institute on Aging and the American Heart Association stated: Men over 50 may not live as long if they have low testosterone. The study looked at death from any cause in nearly 800 men ages 50 to 91 years who were living in a southern California community and who participated in the Rancho Bernardo Study in the 1980s. At the beginning of the study, almost one-third of these men had suboptimal blood testosterone levels for men their age. The men with low testosterone levels had a 33 percent greater risk of death during the next 18 years than the men with higher testosterone. This difference was not explained by smoking, alcohol intake, level of physical activity, or by pre-existing diseases such as diabetes or heart disease.

The new study is the second report linking the deficiency of this sex hormone with increased death from all causes over time, said study author Gail Laughlin, PhD.

External links

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