Thyroid UK
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Does "normal" thyroxine result vary according to height?


I was diagnosed with borderline hypothyroidism more than two years ago now and about 9 months ago got prescribed Levothyroxine (25mcg), then it was upped to 50mcg, now I'm on 75mcg and apparently my blood test results came back as normal. The thing is, I still feel awful, I have been diagnosed moderate to severe depression and anxiety (which I have had on/off problems with this since my teens) and I am quite disappointed because when I was diagnosed with hypothyroidism I stupidly thought it was the answer to all my problems.

I am just under 5 feet tall and am basically wondering if anybody knows whether the measurements take into account differences in size. If the normal result is based on normal for an average sized woman, would that be applicable to me, being fairly less than average in stature.

BTW, this runs in my family as my nan and aunties have it, also my 5 year old was showing a borderline low result but it went back up to normal and I have been told that he doesn't need any follow up/check ups unless he shows symptoms.


8 Replies

Hi Fyffee

If you could get a print-out/copy from the doctors of your last blood test results, with the ranges, and post them on a new question for members to comment. Unless you have them to hand now.

Don't accept the word 'normal' with regard to thyroid gland blood tests - it's how you feel that is the main thing. If you feel unwell, you need increase in meds and they should take account of clinical symptoms, except doctors don't know what they are. I think there are about 100 roughly. You may need the addition of T3 into your medication as that helps some people who don't convert levo into sufficient T3 for their needs.

If you've not had recent blood tests, ask for B12, Vit D, iron, ferritin and folate to be tested as we are usually deficient. Just say you need another test as you are feeling unwell.


Thanks, I only had my last test 2 months ago and didn't get my results via appointment, but over the phone so didn't get any actual figures. My GP is actually a lovely man and I will see if I can get a copy of all my test results for comparison.

I really want to get it sorted out, especially as I have a son to look after.


Body size does affect dose, but I have never come across anything that suggests a relationship of test results with height. As a very broad brush, doses rise with body mass, but that is not much of a surprise. And there are many other factors which affect dose.

However, I did turn this up, which might be good news for you!

Cancer Res. 2014 Jan 1;74(1):235-42. doi: 10.1158/0008-5472.CAN-13-2228. Epub 2013 Nov 18.

Childhood height and body mass index were associated with risk of adult thyroid cancer in a large cohort study.

Kitahara CM1, Gamborg M, Berrington de González A, Sørensen TI, Baker JL.

Author information

1Authors' Affiliations: Division of Cancer Epidemiology and Genetics, National Cancer Institute, NIH, Rockville, Maryland; Institute of Preventive Medicine; Bispebjerg and Frederiksberg Hospitals, The Capital Region, Copenhagen; and Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.


Taller stature and obesity in adulthood have been consistently associated with an increased risk of thyroid cancer, but few studies have investigated the role of childhood body size. Using data from a large prospective cohort, we examined associations for height and body mass index (BMI) at ages 7 to 13 years with risk of thyroid cancer in later life. The study population included 321,085 children from the Copenhagen School Health Records Register, born between 1930 and 1989 in Copenhagen, Denmark, with measurements of height and weight from 7 to 13 years of age. These data were linked with the Danish Cancer Registry to identify incident thyroid cancer cases (1968-2010). Hazard ratios (HR) and 95% confidence intervals (CI) were calculated for age- and sex-specific height and BMI SD scores (SDS) using proportional hazards models stratified by birth cohort and sex. During follow-up (median = 38.6 years), 171 women and 64 men were diagnosed with thyroid cancer. Both height and BMI were positively associated with thyroid cancer risk, and these associations were similar by age at measurement. Using age 10 as an example, HRs per 1 unit increase in SDS for height (~6-7 cm) and BMI (~1.5-2 kg/m(2)) were 1.22 (95% CI, 1.07-1.40) and 1.15 (95% CI, 1.00-1.34), respectively. These results, together with the relatively young ages at which thyroid cancers are diagnosed compared with other malignancies, suggest a potential link between early-life factors related to growth and body weight and thyroid carcinogenesis.





Thanks for the reply. You're right, that article is good news. :)


No has nothing to do with hight! The meds are prescribed per weight sometimes, but blood tests dont vary by any of these 2 parameters:-)


Think I'm clutching at straws really, just hoping that something simple is the "answer" and I can sort myself out.

Thanks for your reply.


regarding your son.......i found something--its crucial for young brains to have enough thyroid hormons

Brain biogenic amines and altered thyroid function

However, when the replacement therapy was postponed until adulthood, L-triiodothyronine failed to produce any restorative effects, suggesting that a critical period exists in early life during which thyroid hormone must be present to permit normal developmental pattern of central amines.


Normal for one person might not be normal for another. Replacement levo should be raised until the patient feels well, so I think that you need more meds. Even if you are just about 5ft I think that you need more levo. I knew a lady who was about your height and she was on 175 mcg of levo and she was in her 70's.


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