Secondary hypothyroidism

[Dryski]

Has anyone had problems with central hypothyroidism and their tsh going to zero. Doctor refusing to raise levothyroxine because it will suppress tsh to much but my free t4 really needs a raise. Does a low tsh really cause afib and osteoarthritis or is this false.

[SlowDragon Administrator]

Does a low tsh really cause afib and osteoarthritis or is this false.

It’s false …..provided that Ft3 is within range

LEVO DOSE SHOULD NOT BE DETERMINED BY TSH

Diogenes/Toft paper:

bmcendocrdisord.biomedcentr...

healthunlocked.com/thyroidu...

The link between TSH, FT4 and FT3 in hyperthyroidism is very different from taking thyroid hormone (T4) in therapy. In hyperthyroidism, FT4 and FT3 are usually well above range and TSH is very low or undetectable. In therapy, FT4 can be high-normal or just above normal, TSH can be suppressed but FT3 (the important hormone that controls your health) will usually be in the normal range. FT4 and TSH are of little use in controlling therapy and FT3 is the defining measure. A recent paper has shown this graphically:

Heterogenous Biochemical Expression of Hormone Activity in Subclinical/Overt Hyperthyroidism and Exogenous Thyrotoxicosis

February 2020 Journal of Clinical and Translational Endocrinology 19:100219

DOI: 10.1016/j.jcte.2020.100219

LicenseCC BY-NC-ND 4.0

Rudolf Hoermann, John Edward M Midgley, Rolf Larisch, Johannes W. Dietrich

LlINK TO PAPER:

ncbi.nlm.nih.gov/pubmed/320...

sciencedirect.com/science/a...

also

academic.oup.com/jcem/artic...

Interestingly, patients with a serum TSH below the reference range, but not suppressed (0.04–0.4 mU/liter), had no increased risk of cardiovascular disease, dysrhythmias, or fractures. It is unfortunate that we did not have access to serum free T4 concentrations in these patients to ascertain whether they were above or within the laboratory reference range. However, our data indicate that it may be safe for patients to be on a dose of T4 that results in a low serum TSH concentration, as long as it is not suppressed at less than 0.03 mU/liter. Many patients report that they prefer such T4 doses (9, 10). Figure 2 indicates that the best outcomes appear to be associated with having a TSH within the lower end of the reference range.

If GP says " I have to reduce your dose because the guidelines say i can't let you have a below range TSH" .....

The first paragraph in the NICE (NHS) Thyroid Disease, Assessment and Management guidelines says :

nice.org.uk/guidance/ng145

"Your responsibility

The recommendations in this guideline represent the view of NICE, arrived at after careful consideration of the evidence available. When exercising their judgement, professionals and practitioners are expected to take this guideline fully into account, alongside the individual needs, preferences and values of their patients or the people using their service. It is not mandatory to apply the recommendations, and the guideline does not override the responsibility to make decisions appropriate to the circumstances of the individual, in consultation with them and their families and carers or guardian. "

heart.bmj.com/content/84/4/...

Over replacement with thyroxine?

There is some concern that administering thyroxine in a dose which suppresses serum TSH may provoke significant cardiovascular problems, including abnormal ventricular diastolic relaxation, a reduced exercise capacity, an increase in mean basal heart rate, and atrial premature contractions.12 Apart from an increase in left ventricular mass index within the normal range, these observations have not been verified.13 Moreover, there is no evidence, despite the findings of the Framingham study, that a suppressed serum TSH concentration in a patient taking thyroxine in whom serum T3 is unequivocally normal is a risk factor for atrial fibrillation.

Low TSH no heart issues

academic.oup.com/jcem/artic...

In summary, patients on long-term T4 with either an increased serum TSH (>4 mU/liter) or a suppressed TSH (<0.03 mU/liter) have an increased risk of cardiovascular disease, dysrhythmias, and fractures when compared with patients with a TSH within the laboratory reference range. Patients with a low, but not suppressed, TSH (0.04–0.4 mU/liter) had no increased risk of these outcomes in this study.

Atrial fibrillation can occur with low Ft3 or low Ft4

pubmed.ncbi.nlm.nih.gov/175...

Osteoporosis

thyroidpatients.ca/2018/07/...

Osteoporosis and iron deficiency

healthunlocked.com/thyroidu...