Hypothyroidism following gastric sleeve surgery resolved by ingesting crushed thyroxine tablets

Insight of the Biopharmaceutical Implication of Sleeve Gastrectomy on Levothyroxine Absorption in Hypothyroidism Patients

PURPOSE

The growing rate of obesity led to an increased number of bariatric surgeries (BS) as a treatment option for obesity. The gastrointestinal tract (GIT) changes following BS can impact many drugs' absorption. Levothyroxine (LT4) is a synthetic thyroxine (T4) replacement used commonly as tablets to manage hypothyroidism disorder, which is more prevalent among patients with obesity. This study aims to examine the LT4 oral tablet form therapy after sleeve gastrectomy.

MATERIALS AND METHODS

A retrospective cohort study was conducted in multi-center. The LT4 doses and TSH and T4 levels were compared before and after BS. The post-surgery readings were categorized into three periods: (one to three months), (four to six months), and (> six ) months after surgery. ANOVA test was used for analysis.

RESULTS

A total of 14374 patients who underwent BS from (1/2019 to 3/2022) were screened for eligibility, and n = 101 participants matched the inclusion criteria. The TSH and T4 were not statistically significant differences before and after surgery (P-values of 0.4864 and 0.5970, respectively). However, the doses significantly differed before and after surgery in all the follow-up time point periods (P < 0.002).

CONCLUSION

The LT4 required doses significantly reduced after sleeve gastrectomy, which can be related to the improved endogenous thyroid production in patients with obesity. However, the abnormality of the GIT induced by the sleeve gastrectomy may affect the exogenous LT4 absorption. Using liquid forms of LT4 while monitoring the thyroid function parameters can optimize the treatment after the procedure.

Antiallergic Treatment of Bariatric Patients: Potentially Hampered Solubility/Dissolution and Bioavailability of Loratadine, but Not Desloratadine, Post-Bariatric Surgery

Gastrointestinal anatomical/physiological changes after bariatric surgery influence variables affecting the fate of drugs after ingestion, and medication management of these patients requires a thorough and complex mechanistic analysis. The aim of this research was to study whether loratadine/desloratadine antiallergic treatment of bariatric patients is at risk of being ineffective due to impaired solubility/dissolution. The pH-dependent solubility of loratadine/desloratadine was studied in vitro, as well as ex vivo, in gastric content aspirated from patients before versus after bariatric surgery. Then, a biorelevant dissolution method was developed to simulate the gastric conditions after sleeve gastrectomy (SG) or one-anastomosis gastric bypass (OAGB), accounting for key variables (intragastric volume, pH, and contractility), and the dissolution of loratadine/desloratadine was studied pre- versus post-surgery. Dissolution was also studied after tablet crushing or syrup ingestion, as these actions are recommended after bariatric surgery. Finally, these experimental data were implemented in a newly developed physiologically based pharmacokinetic (PBPK) model to simulate loratadine/desloratadine PK profiles pre- versus post-surgery. For both drugs, pH-dependent solubility was demonstrated, with decreased solubility at higher pH; over the pH range 1-7, loratadine solubility decreased ∼2000-fold, and desloratadine decreased ∼120-fold. Ex vivo solubility in aspirated human gastric fluid pre- versus post-surgery was in good agreement with these in vitro results and revealed that while desloratadine solubility still allows complete dissolution post-surgery, loratadine solubility post-surgery is much lower than the threshold required for the complete dissolution of the drug dose. Indeed, severely hampered loratadine dissolution was revealed, dropping from 100% pre-surgery to only 3 and 1% post-SG and post-OAGB, respectively. Tablet crushing did not increase loratadine dissolution in any post-bariatric condition, nor did loratadine syrup in post-OAGB (pH 7) media, while in post-laparoscopic SG conditions (pH 5), the syrup provided partial improvement of up to 40% dissolution. Desloratadine exhibited quick and complete dissolution across all pre-/post-surgery conditions. PBPK simulations revealed pronounced impaired absorption of loratadine post-surgery, with 84-88% decreased C_max, 28-36% decreased F_a, and 24-31% decreased overall bioavailability, depending on the type of bariatric procedure. Desloratadine absorption remained unchanged post-surgery. We propose that desloratadine should be preferred over loratadine in bariatric patients, and as loratadine is an over-the-counter medication, antiallergic therapy after bariatric surgery requires special attention by patients and clinicians alike. This mechanistic approach that reveals potential post-surgery complexity, and at the same time provides adequate substitutions, may contribute to better pharmacotherapy and overall patient care after bariatric surgery.

The Effect of Different Types of Bariatric Surgery on Levothyroxine Requirement in Hypothyroid Bariatric Patients

Background

Bariatric surgeries are carried out to improve a patient's quality of life, and to reduce respiratory, cardiac, endocrine, and metabolic complications encountered by those with high body mass index (BMI). A complication associated with high hypothyroidism is weight gain, which may lead to obesity. Here, we explore the effect of different bariatric procedures on thyroid function and levothyroxine dosage. 

Methods

This is a retrospective review of 887 patients referred to a tertiary bariatric service between 2008 and 2020 and treated for hypothyroidism at the time of referral.

The study identified 57 patients on thyroxine replacement. Of these, 22 underwent restrictive bariatric procedures, 16 underwent restrictive/malabsorptive procedures, and 19 did not undergo operative intervention.

Comparisons were made among each group throughout the timeline of interest.

Results

Out of 57 patients, 50 (87.7%) were female. The average age for patients was 47.26+/- 8.89 years. The average BMI at baseline was 48.72+/- 8.68 kg/m2. The mean dose of levothyroxine in controls was 115.8+/- 53.5 mcg while that of surgical patients was 149.8+/- 68.4 mcg.

There were no statistically significant differences in levothyroxine doses between surgical and control at T0 (baseline), T1 (one-year post-op in surgical patient, or two-year post referral in control patient), T2 (two-year post-op in surgical patient, or three-year post referral in control patient), and T3 (most recent result available). The surgical group was then categorized further into restrictive and restrictive/malabsorptive. When they were compared with the control group, there were no statistically significant differences in doses.

A generalized linear mixed model was applied to assess differences in levothyroxine dose with time as a random variable. This was adjusted for age, sex, BMI, T4 level, and hypothyroid cause. Through this assessment, there were several statistically significant differences in levothyroxine dosage between the groups. Control group required on average 28.06 mcg less levothyroxine than the restrictive/malabsorptive group (p=0.015). Also, the restrictive group required on average 23.57 mcg less levothyroxine than the restrictive/malabsorptive group (p=0.033). There were no statistically significant differences observed between the control group and the restrictive group (p=0.67)

Conclusion

Patients who have bariatric surgery have changes to their anatomy and physiology which may affect both their thyroid hormone homeostasis and levothyroxine pharmacokinetics. Thus, hypothyroid bariatric patients requiring levothyroxine must have their thyroid function monitored regularly. In this study, it was found that hypothyroid patients who underwent restrictive surgery had an overall statistically significant lower levothyroxine requirement to remain euthyroid as compared to the restrictive/malabsorptive group (p=0.033). Additionally, the control group required statistically significantly less levothyroxine than the restrictive/malabsorptive group (p=0.015). These factors may determine the type of surgery chosen by hypothyroid bariatric patients. However, further studies that are randomized, controlled, and multi-center with a higher population are required.