Propanolol

[haggisplant]

Hi

I was always under the impression that propanolol reduced thyroid hormones (peripheral conversion of t4-t3) and so also raised tsh.

Tsh is still not right at 2.5 despite on my usual dose when not taking propanolol. I’d been taking one a week (80 slow release), and said to Gp I thought it could be the propanolol.

He said they didn’t do that and looked it up and couldn’t find anything. But it does mention contraindications in both leaflets and I also found the comment about peripheral conversion here:

medicines.org.uk/emc/produc...

When I took them daily I had to have more thyroxine- in retrospect it’s possible I just needed more but I’m skeptical.

Any experience?

I’m going to stay off them and get a repeat test soon but I do feel hypo so getting impatient!

[Lalatoot]

Propranolol decreases plasma T3 and increases plasma rT3 in a dose-dependent manner due to a decreased production rate of T3 and a decreased metabolic clearance rate of rT3, respectively, caused by inhibition of the conversion of T4 into T3 and of rT3 into 3,3'-T2. This inhibition of 5'-deiodination is not secondary to inhibition of thyroid hormone transport across the plasma membrane. Propranolol and its major metabolite, 4-hydroxypropranolol, are not directly responsible for these effects, but an unidentified metabolite of propranolol might be involved. beta-blockers ameliorate clinical symptoms and signs of thyrotoxicosis independent of the decrease of plasma 13, that is confined to beta-blockers with membrane-stabilizing activity, such as propranolol and alprenolol. The decrease of plasma T3, however, appears responsible for some of the metabolic responses to beta-blockers.

ncbi.nlm.nih.gov/pubmed/168...

[RedApple in reply to Lalatoot]

Another reference:

Beta blockers and corticosteroids that only inhibit the peripheral conversion of T4 to T3 interfere minimally with thyroid function test results. Propranolol hydrochloride (>160 mg/d), atenolol, and metoprolol tartrate produce small reductions in total T3 levels. ncbi.nlm.nih.gov/pmc/articl...

[RedApple]

As I understand it, Propranolol is not itself an addictive substance. But you can become psychologically dependent on it, because it can give a feeling of relaxation. Hence the reason why it's often prescribed for anxiety.

It is frequently used in the treatment of hyperthyroid symptoms. I was very grateful for it myself when I was rushed to A&E because of ongoing frequent episodes of SVT. As you say, your GP should have taken your husbands heart rate into account before prescribing.

[SlowDragon Administrator]

Similar experience......despite seeing 6 different endocrinologists.....not one suggested propranolol was a problem

It is EXTREMELY difficult to ween off, generally

But especially when hypothyroid as thyroid levels have to adjust to reducing dose of propranolol