Will a blood test to assess a hormone level provide a guide to treatment?

Hormone tests may indicate the diagnosis and indicate the nature of the treatment that is required. There are only a few occasions when hormone levels help us to determine the dose that is required. To begin with, there tends to be a wide range of normal levels. Let us consider the case of hormone replacement therapy. An oestradiol (oestrogen) level between 200 and 800 pmol /l would be acceptable. Some patients may feel well at levels towards the lower end of the normal range whilst others seem to need more. Furthermore, we are measuring the concentration of just one of many hormones. If we use the analogy of music, even when an orchestra conductor achieves the sound he is seeking, not everyone in the audience will be happy as we all have different preferences. Similarly, the patient's assessment of her well-being plays a more important role in adjusting treatment than blood hormone levels. In infertility, progesterone estimations provide a helpful guide as to whether ovulation is occurring (Q9.17). Serial testosterone estimations are appropriate when testosterone is being prescribed (Q 28.24).Occasionally hormone levels show surprising readings. When this occurs, the doctor may suggest repeating the test to exclude an error somewhere in the system.

A 33-year-old lady with a history of hirsutism (excessive body hair), had been happy with her hormone treatment. At one routine review, she reported a slight increase in her hirsutism. Her testosterone level was reported to be four times the maximum normal level. A second blood sample was sent and a similar level was found. With such a high reading we needed to exclude a hormone secreting tumour of an ovary or adrenal gland but ultrasound examination found no evidence for this. A further blood sample was sent to a different laboratory which found a normal reading. The first laboratory reported the problem to the company supplying their test package. Investigation showed that the patient's medication produced a previously unsuspected problem with the test.

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