Thyroid UK
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Cortisol Level - is there a part of the range which is best? Also serum FSH, LH and Prolactin - any ideas on these?

Just a quick question. My cortisol result is in range. But it's in the lower part. Is it best to have a cortisol reading at the top end of the range? I ask for two reasons:

1) I suffer chronic dehydration and I was reading low cortisol can interfere with hydration levels

2) I suffer high heart rate (and although there is some slight affect from medication though not much) I think it is being interfered with by adrenaline and in fact the NDT/T3 I take has reduced the thyroid induced tachycardia I was suffering. It's a careful balance on a narrow line.

The cortisol results are as follows:

----- Serum cortisol 474 nmol/L (200 - 700) serum range applicable to 9,00am sample

I have no idea what these are or what they mean? Any ideas?

----- Serum FSH 3 IU/L (1-10)

----- Serum LH 2 IU.L (1-13)

----- Serum Prolactin 377 mIU/L (50-600)

After reading comments here on thyroid hormone ranges e.g. TSH suppressed, Free T4 at the top of the range or slightly above and Free T3 at the top of the range, I wondered if the same was true of cortisol?

Any thoughts on this is much appreciated.

Have a good Easter


5 Replies

Hi deskplant

I only know a little about the last 3 hormones. FSH is follicle stimulating hormone and it stimulate growth of the follicle, LH is Luteinizing hormone this stimulates ovulation, prolactin is the hormone you produce when you lactate but also can indicate hypothyroidism apparently. The first 2 hormones are produced at different times in your cycle but can also indicate if you are perimenopausal. Hope this helps.



OK, that's very helpful indeed. Thanks so much for this. The low prolactin then may be why hypo thyroid mothers find it hard / impossible to breast feed.


What time of the day was your blood sample taken? As you can see the optimum time to do is is before or at 9.00am. If it is done at any other time then the results have to be read according to the time it was done. There is a graph that the Endos work from which give them an idea of where you should be.


9.00am ish?? it lists it as that and it probably was early but now I think it was later than that around 10.30 though I don't know if it makes a difference?


Hello, Can you tell me what that graph is and where I might find it? Thank you


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