Changes in TSH levels in athyreotic patients with differentiated thyroid cancer during levothyroxine therapy: influence on dose adjustments

Factors influencing TSH suppression efficacy in postoperative papillary thyroid carcinoma patients: a retrospective cohort study

OBJECTIVES

While surgery plays a crucial role in treating papillary thyroid carcinoma (PTC), the potential effects of subsequent TSH suppression therapy on prognosis should not be overlooked. This study aims to investigate the factors that influence postoperative TSH suppression therapy in patients with PTC.

METHODS

This study was a retrospective cohort study conducted at our hospital. It included 268 patients who underwent surgery and were pathologically diagnosed with PTC between February 2019 and February 2021. The selected patients received postoperative TSH suppression therapy. Based on the TSH level measured 12 months after surgery, the patients were divided into two groups: TSH level conforming group (n = 80) and non-conforming group (n = 188). We then compared the general clinical data, clinicopathological characteristics, preoperative laboratory test indicators, postoperative levothyroxine sodium tablet dosage, follow-up frequency, and thyroid function-related indicators between the two groups of patients. The correlation between the observed indicators and the success of TSH suppression therapy was further analyzed, leading to the identification of influencing factors for TSH suppression therapy.

RESULTS

There were no statistically significant differences in general clinical data and clinicopathological characteristics between the two groups of patients (P > 0.05). The proportion of patients with preoperative TSH ≥ 2.0 mU/L was higher in the non-conforming group compared to the TSH level conforming group (P < 0.05), and the ROC curve analysis indicated that the area under the curve for the preoperative TSH index was 0.610 (P < 0.05). The proportion of patients in the TSH level conforming group who took oral levothyroxine sodium tablets at a dose of ≥ 1.4 µg/kg·d after surgery was higher (P < 0.05). The postoperative levels of FT3 and FT4 were higher in the TSH level conforming group (P < 0.05). The results of binary logistic regression analysis indicated that factors "Postoperative TSH level ≥ 2 mU/L", "Levothyroxine sodium tablet dose<1.4 µg/kg·d", and "Combined with Hashimoto thyroiditis" were significantly associated with an elevated risk of postoperative TSH levels failing to reach the target (P < 0.05).

CONCLUSION

Optimal thyroid function in patients with PTC post-surgery is best achieved when adjusting the dose of levothyroxine sodium in a timely manner to reach the target TSH level during follow-up visits.

Prevalence of gastrointestinal disorders having an impact on tablet levothyroxine absorption: should this formulation still be considered as the first-line therapy?

PURPOSE

In patients with hypothyroidism, levothyroxine (LT4) is the treatment of choice, and tablets are the most commonly prescribed formulation. Despite multiple scenarios being reported in the literature with impaired tablet absorption and likely missed TSH targets, it is yet unclear what the implications are for clinical practice and the role of liquid solution (LS) and soft gel (SG) formulations. We have thus conducted a narrative review evaluating the prevalence within the general population of gastrointestinal disorders impacting tablet LT4 absorption.

METHODS

PubMed and Google Scholar were searched until December 2019 for systematic reviews and meta-analyses on the topic. If they could not be retrieved, other types of manuscripts were searched.

RESULTS

Lactose malabsorption and Helicobacter pylori infection represented the most common disorders, with a global prevalence of 68% and 48%, respectively. The prevalence of other conditions, including autoimmune gastritis, bariatric surgery, celiac disease, gastroparesis, giardiasis, liver cirrhosis, or ulcerative colitis, was lower than 20%. Data at regional and country levels were found to be heterogeneous, but at least one in five patients was diagnosed with one disorder.

CONCLUSIONS

The worldwide prevalence of gastrointestinal disorders associated with tablet LT4 malabsorption, including lactose malabsorption and Helicobacter pylori infection, is high. Interactions with drugs or food can further increase this risk. Considering that all studies investigating the impact of switching patients from tablet to LS or SG found an improved thyroid balance, the latter formulations should be considered as first-line therapy for managing hypothyroidism.

Thyroid hormone therapy in differentiated thyroid cancer

Surgery-with or without postoperative radioiodine-is the standard of care for most patients with differentiated thyroid carcinoma (DTC). Thyroid hormone replacement therapy is the mainstay of long-term medical management. Patients treated with total thyroidectomy and some who undergo lobectomy alone require thyroid hormone therapy to restore euthyroidism with normal serum thyroid-stimulating hormone (TSH) levels. Because TSH acts as a growth factor for thyroid follicular cells (including those that are neoplastic), it can potentially affect the onset and/or progression of follicular-cell derived thyroid cancer. For this reason, some patients are placed on thyroid hormone therapy at doses that suppress secretion of TSH (suppression therapy). This mini-review looks at the potential benefits and risks of this practice in patients diagnosed with DTC. Aggressive TSH-suppressive therapy is of little or no benefit to the vast majority of patients with DTC. Practice guidelines, therefore, recommend a graded algorithm in which the potential benefits of suppression are weighed against the associated cardiovascular and skeletal risks. Large randomized controlled studies are needed to confirm the presumed oncological benefits of TSH-suppression and its causal role in adverse cardiac, skeletal, and quality of life effects and to assess the efficacy of TSH normalization in reversing or reducing these effects.