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What Are Hormones: What Do They Do?

Stine Albers

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What are hormones? Hormones are not just any messenger substances – they have a significant influence on both our mental and physical health. Without further ado, we’ll introduce you to the most important hormones and their functions.

Hormones control sex drive, hunger, fatigue, our mood, and much more. It often seems that we are at the mercy of hormonal fluctuations, but there are ways to control them a little – for example, through your diet, sleeping pattern, and exercise. We’ll explore these lifestyle aspects further on in this article.[1]

So, what are hormones, and what do hormones do? You’ll discover more in this article by getting an overview of the best-known hormones and their significance in our body. Not only that, we will explore hormonal imbalance and other issues associated with hormones in the human body.

Find further detailed articles on specific hormones and their function in our body in our Health Portal:

What Are Hormones?

Hormones are biochemical messengers that travel through our bloodstream to tissues or organs in every part of our body, including our brain, heart, skin, and kidneys. They work characteristically slowly and are involved in many different processes in our body, including:[2]

  • Developmental and growth processes
  • Metabolic processes
  • Sexual function
  • Reproduction
  • Emotions and mood
Where are hormones produced in the body? Our endocrine system – that is, glands and parts of glands that release important hormones into our bloodstream – helps to integrate and control our metabolic activity. Well-known endocrine glands that make up our endocrine system include the adrenal glands, pancreas, pituitary gland, thyroid, and also the testes and ovaries.[3]

    What Do Hormones Do?

    It is not possible to generalize about what hormones do because their tasks are wide-ranging and can be extremely varied. That’s why we’ve broken down the role of various hormones in our article.

    What Are the Sex Hormones?

    The sex hormones comprise of estrogen and testosterone. Estrogen is known as the female hormone and testosterone as the male hormone – this is due to the fact that women normally produce more estrogen and men more testosterone. Nevertheless, both hormones play an important role in our bodies, regardless of our gender.

    As the name sex hormone suggests, these hormones are primarily responsible for sex drive and reproduction. If the hormone levels in our bodies decrease, then our libido also suffers at the same time.[4]

    What Does Estrogen Do to the Body?

    Our body produces three types of estrogens: estradiol, estriol, and estrone.

    Estrogens have other functions in a woman’s body besides reproduction and are mainly responsible for puberty in girls. Body parts responsible for estrogen production are the adrenal glands and the ovaries. Among other things, estrogens are responsible for:[4]

    • Armpit and pubic hair growth
    • Growth of the breasts
    • Start of the menstrual cycle
    • Lactic acid formation in the vagina
    • Development of fat in certain parts of the body (buttocks/hips)
    • Appearance of the skin
    • Control of cholesterol levels
    • Bone health

    What Is the Function of Testosterone?

    Testosterone is produced mainly in the testicles in men and in the ovaries in women. In general, testosterone belongs to the androgens – that is, the most important male sex hormones.[5] Like estrogen, testosterone fulfills several functions in the body:[6]

    • Facial, body, and pubic hair growth
    • Growth of the penis and testes
    • Deepening of the voice
    • Bone strength and stability
    • Increase in height during puberty
    • Sperm production and fertility (in men)
    • Blood production
    • Libido
    • Fat loss and muscle growth

    Did you know that your testosterone levels can influence your vitamin D levels? This is just one example of the many interactions between hormones and the processes it carries out in your body. You can find out your testosterone levels by taking a testosterone test, which involves collecting a saliva sample.

      What Is the Function of Cortisol?

      When people talk about stress, they often talk about cortisol. Because this hormone is released by your body as soon as you find yourself in a stressful situation. Affected glands include the adrenal glands, hypothalamus, and pituitary gland. By secreting cortisol, various bodily reactions are triggered, for example:[7]

      • Blood sugar levels are controlled
      • Immune system inflammation improves
      • Blood pressure is maintained 
      • Energy is supplied
      • Metabolism is regulated

      Stress and also the short-term release of cortisol can be very helpful in dangerous situations, for example, so that the body can react quickly. However, if your body is exposed to chronic stress, this can have many possible harmful effects on your health.[8, 9]

      What Does Serotonin Do in the Body?

      Serotonin affects our entire body. It is a hormone and neurotransmitter (chemical messenger in the brain) that makes you happy. This is why it is often referred to as the happiness hormone. This is because the part of your brain responsible for negative emotions is suppressed by serotonin. Together with another neurotransmitter dopamine, serotonin thus counteracts depression, sadness, and anxiety.[10]

      But this hormone not only influences your mood. Serotonin also sends signals in your body that, for example, ensure that your heart beats, activate your muscles and trigger thought processes. It also has an important influence on body temperature, bone health, sleeping, and digestion.[8]

      Serotonin stimulates parts of the brain that control your sleep-wake cycle. Another hormone that, together with serotonin, is essential for your sleep is melatonin.

      What Exactly Does Melatonin Do?

      While serotonin brightens your mood, melatonin makes you feel sleepy. Especially towards the evening, the concentration of this hormone in your body increases and makes you tired. But that’s not all – melatonin also affects other important processes that take place in your body, including:[11]

      • Body temperature
      • Blood pressure
      • Secretion of other hormones
      • Immune system

      Melatonin is produced by the pineal gland in our brain, and its production in our body is strongly dependent on light. You are tired earlier in winter than in summer because the days are also shorter. As you might already know, the artificial light from smartphones and laptops can keep you awake in the evening because it stops your brain from producing melatonin.[12]

      Melatonin supplements can help you relax and improve the quality of your sleep if you regularly find that you are struggling to nod off.

      Why Is Oxytocin Called the Love Drug?

      Oxytocin influences your feeling of happiness along with several other hormones, including serotonin, dopamine, and endorphin.[10] 

      Oxytocin is released when we are close to other people or even animals. Glands involved in its secretion are the pituitary gland and the hypothalamus. Not only is this hormone crucial during childbirth and parent–child bonding, breastfeeding, and male reproduction – during sexual intercourse, large amounts of this so-called love hormone are released.[13] When our body releases this hormone, it makes us relaxed and feel happy.

      Not only physical contact can release oxytocin but also sports and physical activity, such as going for a run.[13] It also plays an important role in sperm activity and motility.[15, 16]

      Did you know that men with high levels of oxytocin sometimes develop an enlarged prostate gland? This can cause difficulties urinating.

      Why Is Insulin Important?

      Insulin, which is secreted from our pancreas, regulates our metabolism and provides the body’s cells with the energy it needs – it does this based on blood sugar levels and other hormones in the body.

      The hormone is responsible for allowing cells in the muscles, fat and liver to absorb sugar from our blood. These cells need sugar or glucose in order to have energy – or it can be converted into fat, if required.[17]

      You probably are aware that insulin is connected with diabetes – whether it’s type 1 or type 2 diabetes or gestational diabetes, which occurs during pregnancies. Apart from some differences in symptoms, all forms of diabetes are caused by the body not being able to secrete enough insulin or the body not being able to effectively use the insulin it produces. 

      This causes the sugar to remain in the bloodstream and overall blood sugar levels to rise. The rise in this long-term blood sugar level triggers many health problems, such as deafness or impaired vision. At the same time, kidneys can be affected, and the risk of strokes increases.[18] The good news is that you can test your long-term blood sugar levels with a health test – either at your doctor’s or at home.

      What Are Some Effects of Thyroid Hormones?

      There are several hormones that are produced in the thyroid gland and secreted from there. In particular, the two hormones thyroxine (T4) and triiodothyronine (T3) influence processes that regulate the development, growth, and metabolism of our body.[19] More specifically, the thyroid gland and its hormones are involved in the following processes:

      • Energy regulation and body temperature
      • Muscle, nerve, heart, circulatory, and digestive activity
      • Emotional well-being
      • Sexuality
      • Weight regulation
      • Physical and psychological development (especially in children)
      • Skin health, hair health, and nail growth

      Your thyroid gland can either be overactive or underactive. If you suffer from hypothyroidism, you may experience a lack of interest or energy, weight gain, cold sensations, constipation, and an overall lower level of performance. Hypothyroidism usually runs in families and is more common in adults – especially in women. Symptoms of hyperthyroidism (an overactive gland) include nervousness, weight loss, heat, and diarrhea.[20]

      What Causes Hormonal Imbalance?

      Hormonal imbalance is when your endocrine system produces too much or little of a certain hormone. Not only large imbalances but also small imbalances can prove problematic. A hormonal imbalance can lead to health problems further on down the line, such as early onset menopause, diabetes, weight gain, weight loss, infertility, and fragile bones. 

      Diagnosing this imbalance and identifying the cause for it can lead to a form of treatment that corrects the imbalance and boosts your overall health and well-being

      What Are Hormones – at a Glance

      What Are Hormones?

      Hormones are messenger substances that fulfill many different tasks in our bodies. They are produced in endocrine glands and released when the body reacts to a certain situation.

      What Do Hormones Do?

      The sex hormones estrogen and testosterone control sex drive and reproduction, among other things. Cortisol, the stress hormone, places your body on alert and can become harmful if you are under constant stress. The happiness hormone serotonin and the sleep hormone melatonin together regulate your wake–sleep rhythm. Oxytocin plays an important role in cuddling and generally in our connection to other people and animals. The thyroid hormones thyroxine and triiodothyronine are essential for vital body functions such as metabolism and growth processes.

      What Causes Hormonal Imbalance?

      Hormonal imbalance is when your glands produce too much or little of a certain hormone. Not only large imbalances but also small imbalances can prove harmful to your health. A hormonal imbalance can lead to health problems further on down the line, such as early onset menopause, diabetes, weight gain, weight loss, infertility, and fragile bones.


      [1] Wehr E. Pilz S. Boehm B. O., März W., Obermayer-Pietsch B. Association of vitamin D status with serum androgen levels in men’, Clin. Endocrinol. (Oxf.), vol. 73(2), pp. 243–248, August 2010, doi: 10.1111/j.1365-2265.2009.03777.x.

      [2] Medline Plus, Hormones’, available at accessed on 8 May 2020.

      [3] Thieme, Endokrine Organe: Überblick’, via medici: leichter lernen - mehr verstehen, available atüberblick, accessed on 8 May 2020.

      [4] Silbernagl S. Despopoulos A., Gray R., Rothenburger A. Taschenatlas Physiologie, 8., revised and extended edition, Stuttgart New York: Thieme, 2012.

      [5] Nieschlag E., Behre H. M., Nieschlag S. Testosterone: Action, Deficiency, Substitution. Cambridge University Press, 2012.

      [6] Heinrich P. C., Müller M., Graeve, L. Hrsg., Löffler/Petrides Biochemie und Pathobiochemie. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014.

      [7] Schwab M. Encyclopedia of Cancer. Springer Science & Business Media, 2011.

      [8] Faller, Adolf; Schünke, Michael, Der Körper des Menschen - Einführung in Bau und Funktion, 17th Edition, Thieme, 2016.

      [9] Gangl K., Birkner G., Kundenkompass Stress-Aktuelle Bevölkerungsbefragung: Ausmaß, Ursachen und Auswirkungen von Stress in Deutschland’, available at, Tech. Krankenkasse, 2009, accessed on 2 March 2018.

      [10] Dfarhud D., Malmir M., Khanahmadi M. Happiness & Health: The Biological Factors- Systematic Review Article’, Iran. J. Public Health, vol. 43(11), pp. 1468–1477, November 2014.

      [11] Claustrat B., Leston J. Melatonin: Physiological effects in humans’, Neurochirurgie., vol. 61(2–3), pp. 77–84, June 2015, doi: 10.1016/j.neuchi.2015.03.002.

      [12] Brown G. M. Light, melatonin and the sleep-wake cycle’, J. Psychiatry Neurosci., vol. 19(5), pp. 345–353, November 1994.

      [13] Magon N., Kalra S. The orgasmic history of oxytocin: Love, lust, and labor’, Indian J. Endocrinol. Metab., vol. 15(7), p. 156, January 2011, doi: 10.4103/2230-8210.84851.

      [14] Feldman R., Gordon I., Zagoory‐Sharon O. Maternal and paternal plasma, salivary, and urinary oxytocin and parent–infant synchrony: considering stress and affiliation components of human bonding’, Dev. Sci., vol. 14(4), pp. 752–761, 2011, doi: 10.1111/j.1467-7687.2010.01021.x.

      [15] Irianti S., Ginandjar A. B. Krisnadi S. R., Effendi J. S., Nataprawira D., Gandamihardja S. Aerobic Exercise and Its Effect on Oxytocin Level and Labor Progression’, IOP Conf. Ser. Mater. Sci. Eng., vol. 180, pp. 012177, March 2017, doi: 10.1088/1757-899X/180/1/012177.

      [16] Fuchs U., Leipnitz C., Lippert T. H. The action of oxytocin on sperm motility. In vitro experiments with bull spermatozoa’, Clin. Exp. Obstet. Gynecol., vol. 16(4), pp. 95–97, 1989.

      [17] Wilcox G. Insulin and Insulin Resistance’, Clin. Biochem. Rev., vol. 26(2), pp. 19–39, May 2005.

      [18] Mayo Clinic, Hyperglycemia in diabetes - Symptoms and causes’, Mayo Clinic, 3 November 2018, available at, accessed on 2 June 2020.

      [19] Köhrle J., Schomburg L., Schweizer U. Schilddrüsenhormone – Zentrale Regulatoren von Entwicklung, Wachstum, Grundumsatz, Stoffwechsel und Zelldifferenzierung’, LöfflerPetrides Biochem. Pathobiochem., pp. 512–527, 2014, doi: 10.1007/978-3-642-17972-3_41.

      [20] Forum Schilddrüse, Die Schilddrüse verstehen’, 15 August 2018, available at, accessed on 26 May 2020.

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