Testosterone

Hormones are nothing but chemicals produced by different glands in our body that control the functioning of numerous other organs and functions of the cells and tissues in our body. Hormones play a major role in the normal functioning of our body. Based on their function, these hormones are classified into categories such as growth hormones, sex hormones and many more. Testosterone is one of the most vital male sex hormone. The testes (or the testicles) are the organs that are responsible for the production of testosterone in males. The hormone testosterone is essential during various stages of our life.¹

Functions

Its function begins with differentiation of the growing baby into a boy, and then it helps in the normal growth during childhood, followed by formation of male specific changes (such as change in voice and physical appearance) during puberty and maintenance of the male reproductive ability and libido during adulthood. Other functions of testosterone include maintenance of muscle mass and bone strength, production of sperm, and the pattern of hair. Furthermore, it may also play a role in the general mood and overall health.^{1, 2}

Production and forms of testosterone

The specialized cells known as Leydig cells present in the testes are responsible for the production of testosterone in case of males. Females also do have some amount of testosterone in their body, which is formed by the ovaries along with other female hormones. The hormone thus produced in the testes is generally present in two forms, the free form and the bound form.^{2, 3} The free testosterone is the form that is available for the body to be utilized. Only about 2% of the total testosterone in the body is the free and readily utilizable form. The bound form as the name suggests is attached to certain other proteins which do not allow their utilization until freed from the protein attachment.³

Variations in testosterone levels

While the production of testosterone is at the peak during puberty it begins to decline gradually after 30 years of age. As age progresses further the level of free testosterone in the body begins to decline gradually.³

The testosterone levels are regulated by a complex interaction between the brain and the testes that is controlled by several other hormones and processes. The testosterone levels vary with age, presence of underlying diseases and administration of medications.⁴

Depression

Depression is generally considered a severe disorder that can result from various underlying causes. It has been estimated that more than 6 million men in the United States suffer from depression. This includes all the males from young to the old. While most of them result from certain underlying mental illness, a significant amount of older men suffer from depression due to age related changes.⁵

The testosterone link to depression

As age progresses, many changes begin to take place in our body. One of the major changes noted is the decrease in the functioning of the various organs. The different processes that were occurring at faster pace during adult life begin to slow down as age progresses. The slowing down of a train as the terminal approaches can be taken as the best example.

Age related changes

Now the testes are also not devoid of these age related changes. Therefore as men begin to age the function of the testes also begins to decline. Many adults also tend to suffer from a disorder known as hypogonadism which is associated with decrease in the size of the testes and also the amount of testosterone production. The major outcome of this change is the reduction in the secretion of testosterone.⁶

Effects of low testosterone

The reduction of testosterone levels may have a multitude of effects on men. Low testosterone levels have been associated with many conditions such as erectile dysfunction, reduction in cognitive function (the mental abilities such as awareness, perception, reasoning, and judgment), alteration of daily life activities, depression, and osteoporosis (increased bone loss).⁷ Among these effects, depression has been given much importance as it has a great impact on the life of the affected individuals.

Low testosterone and depression

Depression is one of the major causes of suicide wherein it was estimated that there are about 10.9 suicide deaths per 100,000 people in the United States. The lack of interest and other day to day activities can drive an individual towards extreme situations.⁸

Low testosterone and andropause

Low levels of testosterone have been linked with increased depression in men and this found to be true especially in case of older adults. The decreasing level of testosterone in aging men has been commonly referred to as the male andropause. This is somewhat similar to menopause in women and is characterized by physical and emotional changes.⁹ The reduction of testosterone levels and the related depression can cause undue stress on these individuals and pushes them towards extreme steps in life.

Relation between depression and low testosterone levels

While the occurrence of andropause in men is a much debated topic the hard truth about reduction in testosterone levels and the related increase in depression levels cannot be over ruled. Several studies such as this one by Eskelinen et al have reported the relation between depression and low testosterone levels.¹⁰ In their study Eskelinen and colleagues noted that depression was directly related to decreased levels of testosterone in the body of the men who were included in the study. Another interesting fact noted was that these men also suffered from dementia (mental disorder characterized by absent-mindedness and confusion about simple tasks).¹⁰

Depression three times higher in men with low testosterone

A study by Hintikka et al also revealed similar results. Further, they reported that the amount of depression was three times higher in men with decreased function of the testes when compared to men with normal testes function. Along with increased incidence of depression, they also noted that reduction in testosterone levels were associated with decreased sexual desire.¹¹

Australian scientist, Almeida and colleagues tested the levels of free testosterone in men and evaluated the presence or absence of depression in these men. It was noted that men with lower levels of free testosterone were more likely to experience depression when compared to men with higher levels of free testosterone.¹² This validates the impact of testosterone hormone on maintenance of the mental status in aging adults.

Testosterone and anti-depressants

Anti-depressant medications are commonly advised for individuals suffering from depression. These medications are associated with improvement in the symptoms of many affected individuals. However, in the case of men who had low testosterone levels, the anti-depressant medications were found to be quite ineffective. Addition of testosterone supplements in men suffering from depression along with low testosterone levels significantly relieved depression.¹³ The findings of this study suggests that low testosterone levels are indeed associated with depression in men and addition of testosterone supplementation in such men also reduces the need of anti-depressant medications.

Significance of testosterone measurement

Measurement of testosterone levels can not only help in identification of low testosterone levels as the probable cause of depression it can also be helpful in predicting the occurrence of depression in men. The population based study by Joshi et al at Amsterdam concluded that free testosterone levels below170 pmol/L (picomoles per liter; a value used to denote levels of hormones) are associated with symptoms of depression while levels below 220 pmol/L can predict the onset of depressive symptoms.⁶ The study highlights the importance of measuring testosterone levels in men especially those who are suffering from depression, lack of libido and other associated features. Random screening of testosterone levels can also be helpful in identifying men who are increased risk of developing depression.

You can discuss the link between testosterone and depression and overall approaches to happiness on the meHacker forum.

References:

1. Gray H. Anatomy of the Human Body. [Accessed: 2009]. Available from: http://www.bartleby.com/107/258.html
2. The patient education institute, Inc. Low testosterone. [updated: 2005; accessed: 2009]. Available from: http://www.nlm.nih.gov/medlineplus/tutorials/lowtestosterone/ur189101.pdf
3. Craig CR, Stitzel RE. Modern pharmacology with clinical applications. Lippincott Williams & Wilkins, 2003.
4. Medlineplus. Testosterone. [updated: 2009 May; accessed: 2009 Jun]. Available from: http://www.nlm.nih.gov/medlineplus/ency/article/003707.htm
5. The National Institute of Mental Health (NIMH). Depression in Men. [updated: 2009 Mar; accessed: 2009 Jun]. Available from: http://www.nimh.nih.gov/health/topics/depression/men-and-depression/depression-in-men.shtml
6. Joshi D, van Schoor NM, de Ronde W, et al. Low free testosterone levels are associated with prevalence and incidence of depressive symptoms in older men. Clin Endocrinol (Oxf). 2009 May 25.
7. Yavuz BB, Ozkayar N, Halil M, et al. Free testosterone levels and implications on clinical outcomes in elderly men. Aging Clin Exp Res. 2008 Jun;20(3):201-6.
8. The National Institute of Mental Health (NIMH). Suicide in the U.S.: Statistics and Prevention. [updated: 2009 May; accessed: 2009 Jun]. Available from: http://www.nimh.nih.gov/health/publications/suicide-in-the-us-statistics-and-prevention/index.shtml
9. Tenover JS. Declining testicular function in aging men. Int J Impot Res. 2003 Aug;15 Suppl 4:S3-8.
10. Eskelinen SI, Vahlberg TJ, Isoaho RE, et al. Associations of sex hormone concentrations with health and life satisfaction in elderly men. Endocr Pract. 2007 Nov-Dec;13(7):743-9.
11. Hintikka J, Niskanen L, Koivumaa-Honkanen H, et al. Hypogonadism, Decreased Sexual Desire, and Long-Term Depression in Middle-Aged Men. J Sex Med. 2009 Apr 28.
12. Almeida O et al. Arch Gen Psychiatry. 2008;65[3]:283-289.
13. Pope HG Jr, Cohane GH, Kanayama G, Siegel AJ, Hudson JI. Testosterone gel supplementation for men with refractory depression: a randomized, placebo-controlled trial. Am J Psychiatry. 2003 Jan;160(1):105-11.