Is It Possible That The Labetalol Was Stopping T4 Conversion Resulting In Hypothyroid?

Posted on Sun, 13 Sep 2020

Medically reviewed by Ask A Doctor - 24x7 Medical Review Team

Sun, 13 Sep 2020 Answered on

Thu, 19 Jun 2025 Last reviewed on

Question : Hi. I take labetalol 50mg BID. I recently started taking a quarter grain of Armour Thyroid for low T3 and T4. Over the past several days I have developed palpitations heart rate hovering around 50. I went to the emergency room this morning because I had developed chest pain. They did cardiac work up all tests were negative except that I was having PVCs and was bradycardic. The ER doc told me to take half of my labetalol Until I can see my PCP. I am worried about taking the labetalol and having my heart rate go even lower. Is there a rebound bradycardia if you stop taking labetalol abruptly Though? Do labetalol and Armour Thyroid work paradoxically? Is it possible that the labetalol was stopping T4 conversion resulting in hypothyroid? The opposite of the intended result?

Answered by Dr. Bhanu Partap (1 hour later)

Brief Answer:
Please refer to the detailed answer below

Detailed Answer:
Hello

After going through the medical details provided by you I can understand your concern for your health and I would like to tell you that labetalol is a non-selective beta blockers and bradycardia is not a commonly reported side-effect with its use.

Armour Thyroid is a natural product made from animal thyroid glands. This can be the reason for your altered cardiac activity. It’s advisable that if you are hypothyroid then kindly discuss with your treating physician and switch to levothyroxine which is a a synthetic compound identical to T4 (levothyroxine) produced by the human thyroid gland.

No labetatlol have no interactions with T4 conversion.

Kind Regards

Above answer was peer-reviewed by : Dr. Kampana