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Pituitary News, Issue 3 - Spring 1997. Testosterone is an essential hormone. Lack of testosterone in men is called male Hypogonadism and it is likely to lead to lower sperm production as well as loss of libido and impotence.
Dr Fred Wu, Manchester Royal Infirmary Testosterone is an essential hormone and its place in the male reproductive system is shown in the diagram below. Testosterone must be present for any sexual activity to take place. It is also necessary for fertility, although it is not enough on its own to accomplish this; the two pituitary Sex hormones (LH and FSH) are also needed. Box. How the pituitary effects testosterone production![[Diagram showing the flow of hormones and messages (including feedback mechanisms) from the hypothalamus to the testes via the pituitary]](/images/stories/articles/test-glands.gif) The Hypothalamus links the brain to the pituitary and sends messages to the pituitary (black line) by means of specialised hormones including gonadotrophin-releasing hormone (GnRH), which activates the pituitary cells which produce sex hormones.
The pituitary reacts to the messages from the hypothalamus by producing various hormones which travel in the bloodstream to other glands. These include the pituitary hormones, Luteinising hormone (LH) and Follicle-stimulating hormone (FSH) which are shown by blue lines. These act on the testes to stimulate production of testosterone and sperm (green lines). The red lines indicate feedback messages which are sent back to the pituitary or hypothalamus to tell them whether more or less hormone is needed to allow normal activity of the testes. End box. Lack of testosterone in men is called male hypogonadism and it is likely to lead to lower sperm production as well as loss of libido and impotence. If hypogonadism starts before puberty, this will prevent puberty taking place unless it is artificially stimulated. There are a number of short- and long-term effects and these are shown in the box below. Box. Features of Testosterone Deficiency| Symptoms | Signs | Long Term Risk |
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- fatigue
- lethargy
- depression
- impotence
- loss of libido
- muscular weakness
- decreased shaving frequency
| - loss of body, facial and pubic hair
- Gynaecomastia (increased breast tissue)
- smooth, fine wrinkly skin, especially face
- reduced testicular volume
| - Osteoporosis can occur in untreated patients, leading to increased risk of hip and spine fractures.
| End box. The pituitary's ability to produce the hormones that stimulate testosterone production can be hindered by a Pituitary tumour or as a result of surgery or Radiotherapy. Blood tests will confirm how much testosterone is circulating and also how much LH and FSH are present. What are the aims of testosterone replacement?Treatment is aimed at removing the symptoms shown in the box above, preventing long-term problems such as osteoporosis, treating the underlying pituitary disease and, if required, helping to induce fertility. Various forms of testosterone therapyTestosterone cannot be taking simply by mouth as the liver would break it down very quickly. The main methods are by deep Intramuscular injection, by implant, orally (in a modified form), or by testosterone patch. InjectionTestosterone esters are deposited deep into muscle. However, some patients experience an unpleasant 'roller-coaster' effect as levels rise and then fall dramatically. In addition, the injections can be painful, although many men do get used to them and can administer treatment themselves. ImplantsTestosterone implants are cylindrical pellets which are inserted in the wall of the abdomen or thigh under local anaethetic. These deliver testosterone over a longer period, with peak amounts after 2-4 weeks, then declining slowly for the rest of a 4-6 month period. OralOral testosterone needs to be taken 3-4 times a day, and it is absorbed from the gut. The body's absorption of it can vary, although this is minimised it if is taken with food. It is only useful for low levels of replacement. Testosterone patches (transdermal testosterone)This is a new form of therapy which involves applying patches to the back, abdomen or thigh. Usually, two patches are applied and changed daily. This allows a fairly constant delivery of testosterone throughout the day, but it can cause skin reactions in some people. Which type of therapy is best for a particular person depends on several factors, including patient preference and local facilities. Almost all patients respond well to the injections. Safety and side-effectsTreatment is usually monitored by gauging improvements in symptoms such as impotence, sex drive and hair, and also by measuring testosterone levels in the blood before the next injection or implant. Side-effects seem to be very rare. They can include acne, erections not due to sexual stimulation (transient priapism), development of breast tissue (gynaecomastia), fluid retention, and a minor increase in the number of red cells present in the blood. Less is known yet about the long-term effects, for instance whether there is any risk of cardiovascular or prostate diseases. Since prostatic diseases are very common in 'healthy' men over the age of 50, patients on testosterone in this age group may also wish to have occasional prostate tests. The dosage is also usually reduced in men over 50, to reflect the decrease in testosterone levels that would normally occur. Testosterone replacement therapy usually leads to an increase in sex drive and increased assertiveness. Some men have questioned whether this could lead to aggressive behaviour, but in practice this is very rare without pre-existing behavioural problems. |
