Why we don't test your FSH, E2, PRL, Free T4 and SBHG.

As you may have noticed, some of the hormones involved in your cycle are not included in your Grip test. Here we explain why.



Follicle Stimulating Hormone (FSH)

FSH is, as the name gives away, a hormone involved in making your follicles grow – it stimulates small, primordial follicles to grow into mature ones, ready to release an egg. Your FSH levels change a lot during your cycle and also in between cycles (reference 1). This makes it difficult to track a one-off blood test.


Like AMH, FSH can be used as a marker of ovarian reserve – that is the technical term for pool of eggs you have left in your ovaries. However, AMH is shown to be a much more accurate predictor of your ovarian reserve and the age you might enter menopause than FSH (reference 2). Therefore, as a first step and to save you some $, we choose to only test your AMH in our screening test.


Estradiol (E2)

Estradiol is one of the three estrogen hormones naturally produced in the body.

Estradiol's main function is to mature and maintain the female reproductive system. During menstruation, Estradiol level increases which allows the egg to be released and implanted once fertilized.


As we already tests your ovulation through LH, unless things are off there, we do not need to dive deeper into E2 yet.


Prolactin

Prolactin is also known as the ‘breast feeding hormone’, but besides its function in milk production it has more than 100 other functions it can impact, such as ovulation, but also regulation of your immune system and even the making of new blood cells.


Besides the wide range of functions of prolactin, there is also an extensive list of things that can influence your prolactin levels. This ranges from certain medications to sexual intercourse and even nipple stimulation (this can raise your prolactin levels – who would have thought!).


As we can never anticipate all the different physiological, pharmacological and pathological causes that can alter your prolactin levels, we’ve opted not to test it, as we are unsure what your underlying cause might be. On top of that, to test your ovulation, we have other hormones available, so we can still say something about the status of your cycle!

Free T4

Your thyroid hormones are tightly controlled via two glands in your brain: the hypothalamus produces thyrotropin releasing hormone (TRH) which in turn stimulates the pituitary to release thyroid stimulating hormone (TSH). TSH will act on your thyroid and prompt the release of T4 and T3. This whole system is kept in balance through (negative) feedback. When there's enough T4, a signal is being sent to decrease the production of TRH and TSH. This negative feedback system makes that the brain knows when to produce more or less TRH & TSH.


To screen for abnormalities in your thyroid function, we choose only to test TSH. If your TSH value is abnormal (either too high or too low), we recommend you get further testing done via your GP to figure out where in the system the problem lies (e.g. in your pituitary or in your thyroid itself). If you have a normal TSH level, then the chances of you having a normal thyroid function are high. It also helps to keep the price of the test down, by only testing your TSH 😊.


Sex Hormone binding Globulin (SHBG)

SHBG is a protein that is produced in your liver and can bind to hormones such as testosterone and oestradiol (which is an oestrogen). High levels of SHBG suggest that there is less ‘free’ testosterone or oestradiol available in your blood, as most of it is bound to SHBG. It can’t do the function that it is meant to do when it is bound.


SHBG tests are not routinely used in routine fertility assessments. However, it can be used in case your doctor wants to know more about why your testosterone or oestradiol levels are high or low. As a first screening step in your Grip test though, there is no need to dive in that deeply!

References

1. Kwee J, Schats R, McDonnell J, Lambalk C, Schoemaker J. Intercycle variability of ovarian reserve tests: results of a prospective randomized study. Human Reproduction. 2004;19(3):590-5.

2. Depmann M, Eijkemans M, Broer S, Scheffer G, Van Rooij I, Laven J, et al. Does anti-Müllerian hormone predict menopause in the general population? Results of a prospective ongoing cohort study. Human reproduction. 2016;31(7):1579-87.


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