Impaired enteral levothyroxine absorption in hypothyroidism refractory to oral therapy after thyroid ablation for papillary thyroid cancer: case report and kinetic studies

Progress Toward and Challenges Remaining for Thyroid Tissue Regeneration

Thyroid hormones play a pivotal role in diverse physiological processes, and insufficient synthesis of these hormones results in hypothyroidism, a prevalent disorder with a significant global impact. Research has shown that the residual thyroid tissue following surgery fails to fully regenerate the gland and restore normal function. The slow turnover rate of the thyroid gland and the presence of resident stem cells, which may contribute to regeneration within adult thyroid tissue, are topics of ongoing debate. This comprehensive review summarizes current research findings concerning the regeneration of the adult thyroid. Investigations have identified potential cellular mechanisms implicated in thyroid regeneration following partial tissue damage, including cells within microfollicles and a cluster of potential thyroid progenitors cells. Nevertheless, the exact mechanisms remain elusive. In cases of complete removal of the thyroid gland, regeneration does not occur, underscoring the necessity for an external source of thyroid tissue. The transplantation of thyroid organoids has emerged as a promising approach to restore thyroid function. Researchers have successfully derived thyroid organoids from various sources and demonstrated their functionality in both in vitro and in vivo animal models. Despite the challenges that still need to be addressed in achieving full maturation and functionality of human thyroid organoids, significant strides have been made in this regard. This review explores the potential of thyroid organoid transplantation and its implications for the field of regenerative medicine.

Decreased Expression of Ileal Thyroid Hormone Transporters in a Hypothyroid Patient: A Case Report

BACKGROUND

Malabsorption of levothyroxine (LT4) is a common problem faced in clinical practice. It is usually solved, if there are no complexities including gastrointestinal absorption disorder, by taking medicines on an empty stomach and avoiding foods interfering with LT4. Herein we present a rare case of a patient exhibiting malabsorption of LT4 with decreased membranous expression of ileal transporters.

CASE

The 22-Year-old female presented with sustained hypothyroid status despite medication of 7.8 μg/kg LT4. Medical history and LT4 absorption test (the absorption rate 8.4%) excluded pseudomalabsorption. No organic gastrointestinal disorder was found in the patient by blood chemistry, endoscopies, and abdominal computed tomography scan. The immunohistochemical analysis showed decreased membranous expression of LAT1 and LAT2 in distal ileum and ascending colon in the patient compared to 20 controls who have no thyroid disease. The expression of MCT8 in colon appeared at both nucleus and brush border in the patient, while it was limited to brush border in controls. The expression of other transporters was similar between the patient and controls.

CONCLUSION

The changes of the expression of LAT1 and LAT2 in this patient showing LT4 malabsorption might help to understand the role of intestinal transporters in the absorption of LT4 in humans. The functional relevance of the decrement of LAT1 and LAT2 in this patient remains to be elucidated.

The Stability of TSH, and Thyroid Hormones, in Patients Treated With Tablet, or Liquid Levo-Thyroxine

Approximately, 5% of the population is affected by hypothyroidism, mainly women and persons aged more than 60 years. After the diagnosis of hypothyroidism the usual therapy is tablet levothyroxine (L-T4), with a monitoring of the thyroid-stimulating hormone (TSH) level in primary hypothyroidism every 6-8 weeks and L-T4 is adjusted as necessary to reach an euthyroid state. Once TSH is stabilized in the normal range, it is recommended to conduct annual testing in the treated subjects to warrant suitable replacement. More recently advances regarding L-T4 treatment are the introduction of new oral formulations: the liquid solution, and soft gel capsule. The soft gel capsule permits a quick dissolution in the acid gastric pH. The liquid preparation does not require an acid gastric environment. Many pharmacokinetic studies demonstrated a more rapid absorption for the liquid L-T4, or capsule, than with tablet. Many studies have shown that the liquid, or capsule, formulations can overcome the interaction with foods, drugs or malabsorptive conditions, that are able to impair the tablet L-T4 absorption. Lately studies have suggested that liquid L-T4 can permit to maintain more efficiently normal TSH levels in hypothyroid patients in the long-term follow-up, than tablet L-T4, both in patients with malabsorptive states, and in those without malabsorption. Further large, prospective, longitudinal studies are needed to evaluate the stability of TSH, in hypothyroid patients treated with different L-T4 formulations.

EMPATHY: A New Tool for Identifying the Most Suitable Thyroxine Formulation in Hypothyroid Patients

Background: Therapy of hypothyroidism is based on the administration of appropriate doses of levothyroxine (LT4). A failure to achieve the thyrotropin (TSH) target may be due to poor compliance with the LT4 therapy in about 60% of cases or to malabsorption in about 40% of cases. No tools are available for detecting malabsorption disorders before the choice of the most appropriate therapy. The aim of this study was to validate the Evaluation of Malabsorption in PATients with HYpothyroidism (EMPATHY) questionnaire and to demonstrate its usefulness in indicating the most appropriate therapy. Methods: EMPATHY consists of seven questions that allow the evaluation of several intolerances and allergies. Three hundred (100 males) newly diagnosed hypothyroid patients were enrolled and randomly assigned to complete an EMPATHY questionnaire (150 patients; group 1) or to a control group (150 patients; group 2). The choice of thyroxine formulation and dose for each group was made on the basis of the questionnaire answers or based on the history. Thyroid hormones and TSH were evaluated at enrollment and then every two months for six months; the number of the dose adjustments in the six months for each patient was recorded. Results: Of the 150 patients in each group, 21 (14%) in group 1 and 42 (28%) in group 2 (p = 0.005) needed more than two dose adjustments within six months. After six months of replacement therapy, six (4%) patients in group 1 and 17 (11%) in group 2 (p = 0.03) did not have appropriately controlled hypothyroidism (TSH ≥2.5 mIU/L). A significantly higher LT4 final dose was found in group 2 (148 ± 33 μg/day) than in group 1 (136 ± 28 μg/day; p = 0.003). Conclusions: Validation of EMPATHY provides endocrinologists with a useful tool in clinical practice, permitting a better personalization of LT4 replacement therapy, a more rapid attainment of the target TSH levels, and a decreased need for dose adjustments after initiating therapy.

Gut microbiota and Hashimoto's thyroiditis

About two third of the human microbial commensal community, namely the gut microbiota, is hosted by the gastrointestinal tract which represents the largest interface of the organism to the external environment. This microbial community co-evolved in a symbiotic relationship with the human beings. Growing evidence support the notion that the microbiota plays a significant role in maintaining nutritional, metabolic and immunologic homeostasis in the host. Microbiota, beside the expected role in maintaining gastrointestinal homeostasis also exerts metabolic functions in nutrients digestion and absorption, detoxification and vitamins' synthesis. Intestinal microbiota is also key in the correct development of the lymphoid system, 70% of which resides at the intestinal level. Available studies, both in murine models and humans, have shown an altered ratio between the different phyla, which characterize a" normal" gut microbiota, in a number of different disorders including obesity, to which a significant part of the studies on intestinal microbiota has been addressed so far. These variations in gut microbiota composition, known as dysbiosis, has been also described in patients bearing intestinal autoimmune diseases as well as type 1 diabetes mellitus, systemic sclerosis and systemic lupus erythematosus. Being Hashimoto's thyroiditis the most frequent autoimmune disorder worldwide, the analysis of the reciprocal influence with intestinal microbiota gained interest. The whole thyroid peripheral homeostasis may be sensitive to microbiota changes but there is also evidence that the genesis and progression of autoimmune thyroid disorders may be significantly affected from a changing intestinal microbial composition or even from overt dysbiosis. In this brief review, we focused on the main features which characterize the reciprocal influence between microbiota and thyroid autoimmunity described in the most recent literature.

Is Parenteral Levothyroxine Therapy Safe in Intractable Hypothyroidism?

CASE

A 32-year old woman was admitted to the hospital due to intractable hypothyroidism refractory to high dose of oral l-thyroxine therapy. She underwent total thyroidectomy and radioactive iodine therapy due to papillary thyroid cancer. After excluding poor adherence to therapy and malabsorption, levothyroxine absorption test was performed. No response was detected. Transient neurologic symptoms developed during the test. She developed 3 attacks consisting of neurologic symptoms during high dose administration. The patient was considered a case of isolated l-thyroxine malabsorption. She became euthyroid after intramuscular twice weekly l-thyroxine therapy.

DISCUSSION

There are a few case reports regarding isolated l-thyroxine. We report successful long term results of twice weekly administered intramuscular l-thyroxine therapy. We also draw attention to neurologic side effects of high dose l-thyroxine therapy.

Diagnosis and management of treatment-refractory hypothyroidism: an expert consensus report

There is a frequently encountered subset of hypothyroid patients who are refractory to standard thyroid hormone replacement treatment and require unexpectedly high doses of levothyroxine. In addition to clinical situations where hypothyroid patients are non-compliant, or where there is the possibility of excipient-induced disease exacerbation (gluten/celiac disease), therapeutic failure may be due to impaired absorption of the administered drug. The common approach to managing patients with unusual thyroxine needs is to escalate the dose of levothyroxine until targeted TSH levels are achieved. This approach can increase the risk for prolonged exposure to supratherapeutic doses of levothyroxine, which increase the chances of adverse outcomes. Repeated adjustments of levothyroxine can also escalate the costs of treatment, as frequent office visits and laboratory tests are required to determine and maintain the desired dose. Clinicians should take a systematic approach to managing patients whom they suspect of having treatment-refractory hypothyroidism. This may include searching for, and adjusting, occult medical conditions and/or other factors that may affect the absorption of levothyroxine, before up-titrating the dose of traditional levothyroxine therapy. Depending on the underlying pathology, another approach that may be considered is to try alternative formulations of levothyroxine that are less susceptible to intolerance issues related to excipients, or, in some cases, to malabsorption. The early discovery of these factors via a thoughtful patient work-up may avoid unnecessary thyroid medication adjustments and their consequences for both patients and clinicians.

Advancements in the treatment of hypothyroidism with L-T4 liquid formulation or soft gel capsule: an update

INTRODUCTION

The most recent advance concerning levothyroxine (L-T4) therapy is the development of novel oral formulations: the liquid preparation, and the soft gel capsule. Areas covered: This review evaluates the most recent clinical studies about these new formulations. The liquid formulation has been shown to overcome: the food and beverages intereference with L-T4 tablets absorption, caused by food or coffee at breakfast; malabsorption induced by the increased gastric pH, resulting from atrophic gastritis, or due to proton-pump inhibitors; and malabsorption after bariatric surgery. The use of liquid L-T4 has been studied also in pregnancy, newborns and infants, suggesting a better bioequivalence than tablets. Finally, liquid L-T4 is more active than tablets in the control of thyroid-stimulating hormone (TSH) in hypothyroid patients without malabsorption, drug interference, or gastric disorders, leading to a hypothesized higher absorption of liquid L-T4 also in these patients. Few studies have evaluated soft gel L-T4 with promising results in patients with malabsorption related to coffee or gastritis. Expert opinion: Liquid L-T4 (and soft gel capsules) are more active than the tablet L-T4 in the control of TSH in hypothyroid patients with gastric disorders, malabsorption, or drug interference, but also in patients without absorption disorders.

Tablet levothyroxine (L-T4) malabsorption induced by proton pump inhibitor; a problem that was solved by switching to L-T4 in soft gel capsule

OBJECTIVE

To report a patient in whom the impaired absorption of tablet levothyroxine (L-T4) due to a proton pump inhibitor (PPI) use was corrected by switching the patient to the soft gel capsule.

METHODS

A woman with Hashimoto's thyroiditis-associated hypothyroidism (serum thyroid-stimulating hormone [TSH] 6.8-9.6 mU/L) had been treated with tablet L-T4 (100 μg/day). Because she used to take pantoprazole just before L-T4 in the morning, TSH failed to normalize (4.4-6.5 mU/L). Thus, the daily dose had been progressively increased to 125 and 150 μg/day, with serum TSH levels of 2.4 and 0.6 mU/L, respectively.

RESULTS

While maintaining pantoprazole, we switched the tablet L-T4 (150 g/day) to a soft gel capsule (125 μg/day; Tirosint® capsule, IBSA, Lugano, Switzerland) and after 2 months, to 100 μg/day. Serum TSH was lower than under the equivalent regimens with the tablet: 0.5 versus 2.4 mU/L (125 μg/day) and 2.4 versus 4.4 to 6.5 mU/L (100 μg/day). Upon switching back to the tablet (100 μg/day), serum TSH increased to 3.2 and 4.7 mU/L and then dropped to 2.7-3.0 mU/L when the dose was increased to 125 μg/day. We also acutely evaluated the intestinal absorption of L-T4 by administering 600 μg LT4 as a tablet or soft gel capsule while maintaining pantoprazole. Pharmacokinetic indices showed better and faster absorption for the soft gel capsule versus tablet (area under the curve [AUC]0-4h = 16,240 vs. 10,960 nmol/L x 4 hours, maximum absorption [Cmax] = 108 vs. 73 nmol/L, and time of maximum absorption [Tmax] = 120 minutes vs. 180 minutes).

CONCLUSION

Confirming in vitro studies conducted by other authors, the soft gel capsule L-T4 is negligibly affected by changes in gastric pH compared to tablet L-T4.

More than one way to skin a thyroid. Managing pediatric hypothyroidism with weekly intramuscular levothyroxine

BACKGROUND

Oral levothyroxine (L-T4) supplementation is usually an effective therapy in pediatric hypothyroidism, except in patients with malabsorption or pseudomalabsorption. In these cases, parenteral L-T4 may be required, but there is a paucity of information about this delivery method in the pediatric population.

CASE PRESENTATION

We present three cases of pediatric patients with primary hypothryoidism unresponsive to oral L-T4 that were successfully treated with intramuscular (IM) L-T4.

CONCLUSIONS

This is the first pediatric case series of successful IM L-T4 therapy in refractory primary hypothyroidism. Our case series demonstrates that once weekly IM L-T4 dosing may be a safe and well tolerated treatment regimen for pediatric patients.

The administration of L-thyroxine as soft gel capsule or liquid solution

INTRODUCTION

Levothyroxine (l-T4) is the mainstay of treating hypothyroidism. The tablet is the traditional formulation of l-T4. Tablet l-T4 malabsorption results from either hindered gastric dissolution of the tablet or binding of l-T4 by sequestrants in the intestinal lumen.

AREAS COVERED

This review provides an overview of the pharmacokinetics of l-T4 formulations available in the market: the tablet, the soft gel capsule and the oral solution. We review literature on the new formulations and anticipate the areas of future research.

EXPERT OPINION

Failure of l-T4 treatment to reach target serum thyroid-stimulating hormone levels generally prompts the physicians to increase l-T4 daily dose. In vitro studies have shown that the soft gel capsule releases the active ingredient more consistently at varying pH than the tablet. In addition, in vivo studies have confirmed the in vitro data and have demonstrated that both the soft gel capsule and the liquid formulation are capable to solve tablet l-T4 malabsorption caused by certain drugs, bariatric surgery or coffee. These new formulations may be attractive also for patients who cannot/do not want to change their (improper) habits of l-T4 ingestion. Finally, the oral solution l-T4 could be suitable for patients who cannot swallow the solid formulations.

When thyroid hormone replacement is ineffective?

PURPOSE OF REVIEW

In this article, we will consider the failure of thyroid hormone replacement therapy to normalize serum thyroid stimulating hormone concentrations. We will review circumstances and causes for failures, discuss pertinent unpublished personal cases of didactical value, and provide practical suggestions for providers encountering patients with similar presentations.

RECENT FINDINGS

Recent data are available on the benefit of novel formulations of levothyroxine therapy on malabsorption.

SUMMARY

Most frequently, reasons for ineffectiveness are noncompliance, inappropriate administration of levothyroxine, gastrointestinal disorders, and drug interactions. The diagnostic work-up should include careful history to elucidate the potential reasons for the ineffective therapy.

A thyroxine absorption test followed by weekly thyroxine administration: a method to assess non-adherence to treatment

OBJECTIVE

For patients who remain hypothyroid despite the administration of what would seem adequate doses of levothyroxine (L-T4), the underlying cause can be difficult to determine. The possibility of a biological cause should first be explored; however, in the majority of cases, poor adherence to medication is likely to be the main cause of treatment failure. When non-adherence is suspected but not volunteered, options to confirm the suspicion are limited. In this study, we identified patients for whom known drugs and pathological causes of L-T4 malabsorption were excluded, and despite often high doses of L-T4, the patients remained hypothyroid.

DESIGN

Using a weight-determined oral L-T4 bolus administration, absorption was initially assessed in 23 patients. In nearly all patients, this was shown to be maximal at 120 min post-ingestion. This was then followed by the continued administration of a weekly T4 bolus for a 4-week period after which TSH and free T4 (fT4) levels were recorded.

RESULTS

All patients showed a rise in fT4 at 120 min following the administration of the L-T4 bolus, with a mean increase of 54±3% from baseline. Following the treatment period, using an equivalent weekly L-T4 dose, which was significantly less than that of the daily dose taken by the patients before the test, TSH reduced from baseline in ~75% of cases.

CONCLUSION

Using this combination of tests allows significant malabsorptive problems to be identified first and then potential non-adherence to be demonstrated. A management plan can then be implemented to increase adherence, aiming to improve treatment outcomes.

Subcutaneous application of levothyroxine as successful treatment option in a patient with malabsorption

Background:

Hypothyroidism can usually be treated effectively by oral levothyroxine supplementation. There are, however, some rare circumstances, when oral levothyroxine application is not sufficient, for example malabsorption, interactions with food or other medications, or various gastrointestinal diseases.

Case Report:

We present a 42 year old woman with refractory and severe symptomatic hypothyroidism after subtotal thyroidectomy in spite of high dose oral levothyroxine supplementation. By stepwise increasing oral levothyroxine dosage up to 2200 micrograms plus 80 micrograms of thyronine, no sufficient substitution could be achieved. After suspicion of enteral malabsorption due to a pathological D-Xylose-test, subcutaneous levothyroxine supplementation was started. Finally, a sustained euthyroid state could be achieved.

Conclusions:

For selected patients who do not respond to oral treatment subcutaneous application of levothyroxine can be a suitable and effective therapy.

A novel formulation of L-thyroxine (L-T4) reduces the problem of L-T4 malabsorption by coffee observed with traditional tablet formulations

The purpose of this work is to evaluate if the coffee-associated malabsorption of tablet levothyroxine (L-T4) is reduced by soft gel capsule. We recruited 8 patients with coffee-associated L-T4 malabsorption including one hypothyroid patient. For 6 months, the patients were switched to the capsule maintaining the L-T4 daily dose. Patients took the capsule with water, having coffee 1 h later (proper habit, PH) on days 1-90, or with coffee ≤ 5 min later (improper habit, IH) on days 91-180. After 6 months, 2 patients volunteered for an acute loading test of 600 μg L-T4 (capsule) ingested with water (PH) or with coffee (IH). In the single hypothyroid patient, the post-switch TSH ranged 0.06-0.16 mU/L (PH) versus 5.8-22.4 mU/L pre-switch (PH) and 0.025-0.29 mU/L (IH) versus 26-34 mU/L pre-switch (IH). In the other 7 patients, post-switch TSH was 0.41 ± 0.46 (PH) versus 0.28 ± 0.20 pre-switch (PH) (P = 0.61) and 0.34 ± 0.30 (IH) versus 1.23 ± 1.47 pre-switch (IH) (P < 0.001). Importantly, TSH levels in PH versus IH habit did not differ post-switch (P = 0.90), but they did pre-switch (P < 0.0001). The proportions of post-switch TSH levels <0.10 mU/L with PH (33.3 %) or with IH (33.3 %) were borderline significantly greater than the corresponding pre-switch levels with PH (10.3 %) (P = 0.088) or with IH (0 %) (P = 0.0096). In the two volunteers, the L-T4 loading test showed that coffee influenced L-T4 pharmacokinetics minimally. Soft gel capsules can be used in patients who are unable/unwilling to change their IH of taking L-T4.

Graves' Disease, Hypoparathyroidism, Systemic Lupus Erythematosus, Alopecia, and Angioedema: Autoimmune Polyglandular Syndrome Variant or Coincidence?

Data on coexisting Graves' disease (GD), hypoparathyroidism, and systemic lupus erythematosus (SLE) are limited. The thyroid and parathyroid glands may be extra sensitive to irradiation damage in an underlying autoimmune condition. A 34-year-old black woman presented with tetanic-like cramps, easy skin bruising, fatigue, weight gain, nocturia and back pain. She was previously diagnosed with GD in 2001 and underwent radioiodine therapy (RAI) in 9/01 using 6 mCi. PostRAI (November 2001) she developed hypocalcemia and hypothyroidism (2/02). In 2007, SLE was diagnosed. In October 2009, s-calcium and PTH were still low at 7.1 mg/dl and 9 pg/mL, respectively, although the patient denied symptoms on vitamin D and calcium supplementation. To identify possible autoimmune damage of the parathyroids, we evaluated the presence of activating antibodies to the CaSR and also analyzed the DNA sequence of all 6 translated exons and flanking intronic sequences of her CaSR gene for a functionally significant CaSR mutation but neither was positive. The initial autoimmune damage to her thyroid and possibly parathyroid glands followed by irradiation of them seems to have contributed to her developing both hypoparathyroidism (11/01) and hypothyroidism (2002). The patient could potentially have had parathyroid autoantibodies in 2001 that disappeared by 2009 when she was tested for them. We consider that the multiple autoimmune conditions developed over the past decade of her life with the concurrent irradiation contributing to her brittle hypoparathyroidism. Select patients with GD and perhaps parathyroid autoantibodies with a slowly developing destructive impact on the parathyroid glands may then develop overt hyoparathyroidism with rather low dose RAI ablation. This patient adds to the evolving spectrum of polyglandular syndrome variants.

A curious case of refractory hypothyroidism due to selective malabsorption of oral thyroxine

There are very few cases in the literature in which refractory persistent hypothyroidism responded only to parenteral doses of levothyroxine and no evidence of any malabsorptive disorder could be identified. Here, we present a rare case of a 35-year-old woman with refractory hypothyroidism who responded only to intravenous doses of levothyroxine. We also discuss possible causes for the same.