Leading Biochemist advocates abandoning fixed reference ranges for TSH

Leading Biochemist Dr Carole Spencer from University of Southern California aacc.org/resourcecenters/ar...

Question: What in your opinion, should be taken into account in a study designed to assess the TSH reference range in a population 60-80 years old? Does the NACB guideline approach for TSH reference intervals apply? Do we need 120 euthyroid volunteers for each decade if we also want to know the TSH reference intervals for each decade of life?

Buenos Aires

Carole A. Spencer, PhD : The NHANES population found a TSH upper limit of 7.5 mIU/L for 80+ year olds (Surks JCEM 92:4575, 2007 Atzmon JCEM 94:1251, 2009). I do not believe we need a TSH population reference range for every decade but we need to educate physicians to expect higher TSH in older patients. The question to treat or not to treat ultimately depends on symptoms, TPOAb, medications and other patient-specific factors. I think we need abandon the concept of a fixed reference range for TSH or tailoring a reference range for every condition. Furthermore, different assays detect different TSH isoforms. In any situation not all of the TSH that we are measuring is biologically active, and an increase in bioinactive TSH may be involved with aging.

Question: Should there be age- and gender-specific reference ranges for TSH? What is the best marker for monitoring hypothuroidims treatment and what is the target value?

Cleveland, OH

Carole A. Spencer, PhD : The target for L-T4 replacement for hypothyroidism is a TSH between 0.5 and 2.0 mIU/L. With regard to the TSH reference range, all thyroid tests have a low index of individuality (IoI is the relationship between the within-person and between-person variability). When a test has a low IoI the population reference range of that test is a weak parameter for detecting disease in the individual. In view of this I see no advantage in fine-tuning TSH reference ranges. I am not aware of gender-specific TSH differences, although population studies show a trend for higher TSH with aging. However the mechanism for this is unclear. Physicians need to interpret TSH relative to patient-specific factors rather than a fixed population range.

Question: WHO indicated that 5 mIU/L was an appropriate cutoff for clinical hypothyroidism in adults. Should that be revised?

Toronto, ON

Carole A. Spencer, PhD : Organizations such as WHO tend to report conservative cut-offs. Note a cut off of 5.0 mIU/L would be inappropriate for 1st trimester pregnancy! The Endocrine Society recommends 3.0 mIu/L for 2nd and 3rd trimester pregnancy and 2.5 mIU/L for the 1st trimester this has been well accepted by our physicians (Abalovich et al JCEM 92: S1-S47, 2007). The diagnosis of hypothyroidism and treatment decisions should be based on patient-specific risk factors (slide 21, Biondi & Cooper Endoc Rev 29:76, 2008) not the upper population reference limit for TSH.

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6 Replies

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  • In my book, the "different TSH isoforms" issue fatally undermines the whole edifice that is TSH testing.

    "They" don't seem even to understand the true biological impact of these isoforms. So how can they ever say it is either OK that they do not get measured, or it is OK that they do get measured as if they were all the same.

    Rod

  • >NHANES population found a TSH upper limit of 7.5 mIU/L for 80+ year olds (Surks JCEM 92:4575, 2007 Atzmon JCEM 94:1251, 2009). I do not believe we need a TSH population reference range for every decade but we need to educate physicians to expect higher TSH in older patients.

    Indeed, the 'normal range' for TSH appears to expand with age.

    >The question to treat or not to treat ultimately depends on symptoms, TPOAb, medications and other patient-specific factors.

    Definitely.

  • Would treatment make any difference to the tsh in older people as I am 60 on t3 t4 and have a tsh of 0.01 and feel really not too bad.

    Jo xx

  • Joanna- under treatment the low TSH is fine and you luckily seem on the right regime.

    'Getting there' is what many find difficult -with the low level of in depth testing leaving it to the individual to keep track on the treatment given [if any] and checking on this site.

    Once under hormone treatment the bodies feedback mechanisms are disrupted, so much that is written on a topic will be conditional on the patients response -and protocol they are under.

  • Surely the cut off point depends on the efficiency of the conversion from T4 to T3.

    If , in elederly people, the TSH drifts up then it would indicate that T3 needs a boost.

    Only if that is then low with no high rT3 [to indicate resistance to using T3] would the high TSH be OK and indicate a sluggisg thyroid- but one that was still working.

    The best level of TSH for >60 yrs is less than 3, acording to my friendly hospital advisor and this shows up on Rods' linked data from the Holtorf medical group.

    I wish Drs would understand that lacking energy, drive and being fed up about not losing mid riff weight is not 'just getting old'.

    Sleep problems, autoimmune tendencies and many other indicators are well known in UAT.

    There's plenty of data about now- and I'm copying the US article, with over 100 refs. to my Dr, right now!

    TSH may be a gold standard in the young and fit- but we don't stay like that for ever.

    About time the 'health' service started to help people be well -and not wait till they're seriously ill.

  • Professor Carole Spencer repeats this

    The diagnosis of hypothyroidism and treatment decisions should be based on patient-specific risk factors (slide 21, Biondi & Cooper Endoc Rev 29:76, 2008) not the upper population reference limit for TSH.

    and with regard to ageing

    ... population studies show a trend for higher TSH with aging. However the mechanism for this is unclear. Physicians need to interpret TSH relative to patient-specific factors rather than a fixed population range.

    The higher TSH in an ageing population may be, as you suggest, a need for more thyroid hormone.

    Remember, that to refuse treatment because of age is against the Disability Discrimination Act, Good Medical Practice and the NHS Constitution. Feeling tired is not a symptom of ageing. Even the conservative WHO (according to Professor Spencer) wants good health in old age.

    BTW WHO definition of health = a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.

    No doctor should say "Its just old age!"

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