Proton pump inhibitor-induced suboptimal response to levothyroxine: A primary care case report
Abstract
Levothyroxine is commonly prescribed in primary care for hypothyroidism patients. Its absorption may be reduced significantly by concurrent medications, especially proton pump inhibitors (PPIs).[1,2] This case report represents a practical example of reduced levothyroxine efficacy due to omeprazole use and highlights key learning points for primary care clinicians.
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Corresponding author: Ahmed YO Ahmed Copyright © 2025 Author(s) retain the copyright of this article. This article is published under the terms of the Creative Commons Attribution Liscense 4.0. Proton pump inhibitor-induced suboptimal response to levothyroxine: A primary care case report Ahmed YO Ahmed * and Ahmed MA Shaddad Haxby Newington Centre (General Practice), Hull, UK. World Journal of Advanced Research and Reviews, 2025, 26(03), 315–316 Publication history: Received on 24 April 2025; revised on 31 May 2025; accepted on 03 June 2025 Article DOI: https://doi.org/10.30574/wjarr.2025.26.3.2181 Abstract Levothyroxine is commonly prescribed in primary care for hypothyroidism patients. Its absorption may be reduced significantly by concurrent medications, especially proton pump inhibitors (PPIs).[1,2] This case report represents a practical example of reduced levothyroxine efficacy due to omeprazole use and highlights key learning points for primary care clinicians. Keywords: Levothyroxine; Proton pump inhibitor; Drug interaction; Hypothyroidism 1. Introduction Hypothyroidism is a very common disorder which necessitates Levothyroxine replacement. Patients on this medication need regular monitoring of thyroid function to assess and adjust medication dose and evaluate if other concurrent medications such as Omeprazole in this case reduce effectiveness of treatment. 2. Case presentation A 55-year-old female with a history of long-term primary hypothyroidism, stable for several years on levothyroxine 100 mcg daily, presented with new symptoms of fatigue and gradual weight gain. Blood results of thyroid function tests showed raised TSH (7.3 mIU/L). She had recently begun omeprazole 20 mg daily for new gastroesophageal reflux disease. Although the first impression was a compliance issue but on detailed review, she revealed taking levothyroxine and omeprazole together with breakfast. The patient was counselled to take levothyroxine 30 minutes before breakfast and to switch from omeprazole to ranitidine. At 8-week follow-up, her bloods showed TSH normalized to 2.5 mIU/L with improved symptoms. 3. Discussion This case implies a clinically relevant and probably under-recognized interaction between PPIs (omeprazole in this case) and levothyroxine. PPIs increase gastric pH lowering acidity, impairing dissolution and reducing levothyroxine absorption and subsequently its effect[3,4] A detailed medication review and advice on administration timing (mainly empty stomach, separate from other drugs are crucial, specially that thyroxine levels increase after 1hour and peaks within 3 hours.[4]
World Journal of Advanced Research and Reviews, 2025, 26(03), 315–316 316 Clinicians in primary care are ideally placed to identify such interactions, adjust therapy, and prevent unnecessary dose adjustments or specialist referrals and provide further advice.[5] Table 1 Examples of medications Known to Interfere with Levothyroxine Absorption [5,6] Drug Class Example(s) Mechanism of Interaction Antacids Calcium carbonate Bind to levothyroxine, reducing absorption Proton Pump Inhibitors Omeprazole Increase gastric pH, impair dissolution Iron Supplements Ferrous sulfate Chelation in gut Bile Acid Sequestrants Cholestyramine Bind thyroid hormone in gut Sucralfate sucralfate Adsorption, delays absorption Ritonavir-containing drugs Ritonavir Induce metabolism, lowering T4 levels lipase inhibitors Orlistat nonspecific adsorption 4. Conclusion This case emphasizes the importance of medication timing and drugs interaction awareness in managing hypothyroidism. Learning Points • Always review new medications in patients with stable chronic conditions. • PPIs can reduce levothyroxine absorption, leading to either subclinical or overt hypothyroidism. • Medication timing and spacing strategies can reduce interaction. • Monitoring thyroid function after initiating a PPI is advisable in patients on levothyroxine Compliance with ethical standards Disclosure of conflict of interest The authors declare that they have no conflicts of interest. Statement of informed consent The patient provided verbal consent for publication of this anonymized case. References [1] Sachmechi I, Reich DM, Aninyei M, et al. Effect of proton pump inhibitors on serum thyroid-stimulating hormone level in euthyroid patients treated with levothyroxine for hypothyroidism. Endocr Pract. 2007;13(4):345–349. [2] Guzman-Prado Y, Vita R, Samson O. Concomitant use of levothyroxine and proton pump inhibitors in patients with primary hypothyroidism: a systematic review. J Gen Intern Med. 2021;36(6):1726–1733. [3] Horn JR, Hansten PD. Drugs affecting levothyroxine absorption. Pharmacy Times. 2016; 82(1). Available from: https://www.pharmacytimes.com/view/drugs-affecting-levothyroxine-absorption [4] Caron P, Tudor C, Grunenwald S. Levothyroxine absorption test with the daily levothyroxine dose in patients with “refractory hypothyroidism”. J Endocr Soc. 2025;9(4):bvaf017. [5] National Institute for Health and Care Excellence (NICE). Hypothyroidism: Levothyroxine – Prescribing information. Clinical Knowledge Summary. [Internet]. UK; [2024 Nov.] Available from: https://cks.nice.org.uk/topics/hypothyroidism/prescribing-information/levothyroxine/ [6] British National Formulary (BNF). Levothyroxine interactions. NICE. [Internet]. UK; [2024-25] Available from: https://bnfc.nice.org.uk/interactions/levothyroxine/