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High prolactin, low T4, normal TSH - what's going on?


I'm new here, I'm a 19 year old female from the UK.

For about 6 months I've had symptoms which seem like possible hypothyroidism: fatigue, depression, mood swings, cold, weight gain (from 54kg to 60kg), terrible memory, poor concentration, joint pain in my knees, lack of energy, feel very weak and faint after exercise, low libido, dry skin (mainly legs), dry hair.

I was originally told it was mild depression and possible PTSD.

However, I went to a different doctor a few months later and asked for a blood test. Results were:

T4 11.7 (range 12.6-21) LOW

TSH 2.58 (range 0.51-4.3)

The doctor suggested it was still most likely depression and referred me for talking therapy (first session tomorrow - the waiting lists are so long!). She then got me tested for PCOS because I had started vomiting on my periods. My periods started when I was nearly 16, have always been irregular and long lasting, and I have never had more than 8 in a year.

This blood test showed:

TSH 1.78 (range 0.51-4.3)

T4 12.8 (range 12.6-21)

Prolactin 1167 (range 102-496) HIGH

LH 9.4 (range 2.4-12.6)

FSH 3.7 (range 3.5-12.5)

A different doctor started me on 25mg of levothyroxine and I started to feel better almost immediately.

5 days after starting levo a blood test showed:

TSH 2.07 (range 0.51-4.3)

T4 14.9 (range 12.6-21)

Prolactin 213 (range 102-496)

Then a third doctor at my follow up said I was just anxious and fixating on possible thyroid issues as my anxiety prevented me from accepting a mental health diagnosis. I do not feel at all anxious, I have no history of anxiety (or any other mental health issues) and I have never been described as an anxious person - I am normally described as a very laid back, positive and cheerful person. Anyway, this doctor refused to renew my levo prescription as he said there was no evidence I needed it, and I am willing to accept he might be correct.

I have another GP appointment in a few weeks to discuss everything as so far none of the 4 doctors I've seen have agreed with each other about what's going on and it's making me feel a bit frustrated.

I have a maternal family history of hypothyroidism (and also MS). I am not on any contraception or medications currently. I take vitamin D supplements every day (apparently it decreases the risk of developing MS)

I basically just want to know if anyone's ever experienced anything similar and if anyone has any thoughts about all this?

Thank's in advance, sorry it's such a long post.

7 Replies

TSH levels vary through the day. If we were looking only at TSH results, the numbers you report could owe their variation to time at which the blood was drawn! TSH is highest early in the day and drops

But your FT4 is right at the bottom of the ranges.

I suspect that, over time, your TSH would have risen further, even if your FT4 stayed about the same.

The pituitary often increases not just TSH but also, as in your case, one or more other products such as prolactin.

In my view, the very fact that even on a low dose, and for just a short time, you had recognisable improvement is sufficient evidence of the need for addiitonal thyroid hormone.


T4 11.7 (range 12.6-21) LOW

TSH 2.58 (range 0.51-4.3)

These results show that the TSH cannot be relied upon in your case. TSH usually rises dramatically as fT4 falls. Thus less emphasis should be placed on the TSH.

You have clear signs and symptoms of hypothroidism which responded to levothyroxine treatement. This confirms hypothyroidism, unless it was a placebo response.

Hypothryodism causes depression and depression can reduce TSH leading to hypothyroidism. This reduced TSH is a different isoform of TSH (a complex molecule) which has reduced bioactivity. So, it is difficult to know whether the hypothroidism is causing depression or vice-versa. I would say it is hypothyroidism leading to depression as your TSH is not low.

I would go with the talking therapy as it might help. Not because I think the root cause is depression but because if you hit your thumb with a hammer you might take a painkiller. It might help you in the short term.

When you see your doctor I would point out the TSH / fT4 discrepancy and the conflicting views of the doctors. I'd also say you got better on levothyroxine and you would like a three month therapeutic trial. You have a large number of hypothyroid symptoms and it's messing up your life. If they talk about risk blah, blah, blah point out that you are young and can monitor your response (pulse and symptoms). It would be a good idea to take someone along with you for support. Be friendly but firm.

I don't know anything about prolactin / PCOS but period problems are very common in hypothyroidism.


One set of prolactin tests indicate you might have a pituitary adenoma which can cause secondary hypothyroidism. Prolactin 1167 (range 102-496) HIGH ~ over 500 is indicative of this, though your second results are in normal range. The first set should have been followed up, being so high. Perhaps ask your GP to refer you for a head MRI scan, as it's important to know, Even if it's only small, it can be enough to mess up your thyroid hormones, & cause depression, & the period problems you have.

I've been self-treating for secondary hypothyroidism for almost two years after several endocrinologists refused to acknowledge my hypo & other hormonal issues were related to my tumour. The Pituitary Foundation has a lot of excellent information, as does Thyroid UK.

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Take it from NOT accept the 'talk therapy' response. I blacked out twice, weight gain at 13 lbs a week (that is NOT a typo) despite healthy eating and strenuous regular exercise, facial hair growth, fatigue, no menstrual cycle, etc. At the prompting of family and close friends, I went to the GP I had for YEARS and explained my symptoms. I am NOT a doctor-runner. She chalked it up to 'being stressed' and prescribed counseling. Because I trusted her and was willing to try anything, I did counseling. Symptoms continued and increased, I returned to the GP. She prescribed more counseling. No changes. TWO YEARS aunt begs me to insist the GP refer me to a specialist so I did. My 'trusted' GP says most women would be thankful to not have a period...I was in my early 30s...ummm...yea, NO.

Long story, short...SEVEN years with a tumor on my pituitary...over my child-bearing years. The specialists I was referred to were a joke (sorry, but these two were). A precautionary MRI revealed the tumor. All this to say, ADVOCATE for your health. Do NOT accept 'talk therapy' as the answer. It's not to say, you have a pituitary tumor but please, I beg you, do NOT be the 'nice girl' like I was and wait two years to get diagnosed. If I can help anyone avoid what I went through, I will. I'm still trying to get my health fully restored. Best of health to you!


If you have a problem with prolactin and low thyroid hormones, you need to be tested for pituitary problems. Might be adenoma, might be secondary hypo - not possible to tell (although TSH is a bit high for secondary hypo). Often you get an MRI or CT scan. Unlikey to be depression.


You should not be judged on TSH unless it is very hgh then it is iirrelevant.


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