Individualised requirements for optimum treatment of hypothyroidism: complex needs, limited options

Pregnancy and postpartum dynamics revealed by millions of lab tests

Pregnancy and delivery involve dynamic alterations in many physiological systems. However, the physiological dynamics during pregnancy and after delivery have not been systematically analyzed at high temporal resolution in a large human population. Here, we present the dynamics of 76 lab tests based on a cross-sectional analysis of 44 million measurements from over 300,000 pregnancies. We analyzed each test at weekly intervals from 20 weeks preconception to 80 weeks postpartum, providing detailed temporal profiles. About half of the tests take 3 months to a year to return to baseline postpartum, highlighting the physiological load of childbirth. The precision of the data revealed effects of preconception supplements, overshoots after delivery and intricate temporal responses to changes in blood volume and renal filtration rate. Pregnancy complications-gestational diabetes, preeclampsia, and postpartum hemorrhage-showed distinct dynamical changes. These results provide a comprehensive dynamic portrait of the systems physiology of pregnancy.

Effect of Radioiodine Treatment on Quality of Life in Patients with Subclinical Hyperthyroidism: A Prospective Controlled Study

Radioiodine treatment (RIT) has a high success rate in both the treatment of hyperthyroidism and improving the quality of life (QoL) of symptomatic patients. In asymptomatic patients with subclinical hyperthyroidism thyroid related QoL outcomes are less well known.

METHODS

Study aim was to evaluate thyroid-related QoL in patients with subclinical hyperthyroidism mostly due to toxic nodular goitre undergoing RIT, compared to a control group of euthyroid subjects. Study design was monocentric, prospective, controlled. Fifty control subjects were enrolled and 51 RIT patients. Most subjects were examined at least twice at an interval of 6 months, with visits immediately before and 6 months after treatment in the RIT group. QoL was estimated with the ThyPRO questionnaire, using its composite scale as primary outcome. Treatment effect was the mean adjusted difference (MAD) between groups over time, using repeated? measures mixed? effects models.

RESULTS

TSH concentrations were lower in the RIT group prior to treatment and recovered thereafter slightly above the level of the control group. Correspondingly, QoL improved significantly after 6 months from a worse level in the RIT group, compared to controls (MAD -10.3 [95% CI -14.9, -5.7], p<0.001). QoL improvements were strong for general items, but less pronounced for the hyperthyroid domain. Compared to controls, thyroid volume, thyroid functional capacity (SPINA-GT) and deiodinase activity (SPINA-GD) were significantly reduced in the RIT group.

CONCLUSION

Patients with subclinical hyperthyroidism improve both biochemically and in their QoL after RIT, compared to controls. QoL assessment should have a wider role in clinical practice to complement biochemical tests and help with treatment decisions.

Hypothyroidism, comorbidity and health-related quality of life: a population-based study

Hypothyroidism is associated with a decreased health-related quality of life (HRQoL). We hypothesized that individuals with hypothyroidism (defined as use of thyroid hormone (TH)) and especially those having an impaired HRQoL are characterized by a high prevalence of comorbid disorders and that the impact of hypothyroidism and comorbidity on HRQoL is synergistic. Presence of comorbidity was based on data obtained using structured questionnaires, physical examination, biochemical measurements and verified medication use. Single morbidities were clustered into 14 different disease domains. HRQoL was measured using the RAND-36. Logistic regression analyses were used to determine the effect of TH use on the odds of having an affected disease domain and a lower score than an age- and sex-specific reference value for HRQoL. TH was used by 4537/14,7201 participants of the population-based Lifelines cohort with a mean (± s.d.) age of 51.0 ± 12.8 years (88% females). Eighty-five percent of the TH users had ≥1 affected disease domain in contrast to 71% of nonusers. TH use was associated with a higher odds of 13 out of 14 affected disease domains independent of age and sex. In a multivariable model, TH use was associated with a decreased HRQoL across six out of eight dimensions. No significant interactions between TH use and affected disease domains were observed. TH users with an impaired HRQoL had significantly more comorbidity than those not having an impaired HRQoL. In this large, population-based study, we demonstrated that TH users had more comorbidity than individuals not using TH. The coexistence of other chronic medical conditions in subjects with TH use led to further lowering of HRQoL in an additive manner.

Fast Track Treatment of Hypothyroidism with Levothyroxine: Reaching Homeostasis within Four Weeks

With the current clinical method for the treatment of hypothyroidism the target for the optimum individual values for free thyroxine concentrations [FT4] and thyrotropine concentrations [TSH] of the specific patient are unknown. This situation leads to unnecessary long experimental medication administration that can take a period of sometimes one year. In this article a method will be described where hypothyroid patients are characterized with weekly measured FT4 and TSH concentrations during the first three weeks of synthetic thyroxine or levothyroxine (L-T4) treatment to predict their optimum [FT4] and belonging [TSH] endpoint for a euthyroid homeostatic state. The treatment with levothyroxine will start for all patients with a reference dose of 100 µg, which can be adjusted by the treating physician to a more safe and appropriate dose for the individual which is monitored with weekly thyroid function tests to observe the progress. After three weeks all characteristics of the patient can be inferred from the measured data. The final titration target together with the individual thyroxine half life can be calculated. With the known characteristics and the L-T4 titration target the clinician or treating physician has an instrument to reduce the experimental treatment burden for the patient from one year to a maximum of four weeks.

Levothyroxine therapy, calculated deiodinases activity and basal metabolic rate in obese or nonobese patients after total thyroidectomy for differentiated thyroid cancer, results of a retrospective observational study

INTRODUCTION

Therapy for hypothyroid obese patients is still under definition since the thyrotropin-stimulating hormone (TSH) level is a less reliable marker of euthyroidism than nonobese patients. Indeed, TSH levels positively correlate with body mass index (BMI), and this increase may be a compensatory mechanism aimed at increasing energy expenditure in obese people. In contrast, the correlation of BMI with thyroid hormone levels is not completely clear, and conflicting results have been obtained by several studies. The L-T4 replacement dose is more variable in obese hypothyroid patients than in nonobese patients, and a recent study indicated that the L-T4 replacement dose is related to lean body mass in obese thyroidectomized patients. We aimed to study the correlations of L-T4-administered dose, thyroid hormone levels and TSH secretion with basal metabolic rate (BMR) and total calculated deiodinase activity (GD) in obese and nonobese athyreotic patients. We also looked for individualized L-T4 replacement dose set points to be used in clinical practice.

METHODS

We studied retrospectively 160 athyreotic patients, 120 nonobese and 40 obese. GD was calculated by SPINA Thyr 4.2, the responsiveness of the hypothalamic/pituitary thyrotrope by Jostel's thyrotropin (TSH) index and BMR by the Mifflin-St. Jeor formula, the interplay of GD and BMR with L-T4, thyroid hormones and TSH index (TSHI) was also evaluated.

RESULTS

In our study, the L-T4 dose was an independent predictor of GD, and approximately 30% of athyreotic patients under L-T4 therapy had a reduced GD; FT4 levels were higher and negatively modulated by BMR in obese athyreotic patients respect to nonobese, in these patients a T4 to T3 shunt, in terms of TSHI suppression is observed suggesting a defective hypothalamic pituitary T4 to T3 conversion and a resistance to L-T4 replacement therapy.

CONCLUSIONS

L-t4 dose is the most important predictor of GD, BMR modulates T4 levels in obese athyreotic patients that are resistant to L-T4 replacement therapy.

The role of supporting and disruptive mechanisms of FT3 homeostasis in regulating the hypothalamic-pituitary-thyroid axis

BACKGROUND

Thyroid hormones are controlled by the hypothalamic-pituitary-thyroid (HPT) axis through a complex network of regulatory loops, involving the hormones TRH, TSH, FT4, and FT3. The relationship between TSH and FT4 is widely used for diagnosing thyroid diseases. However, mechanisms of FT3 homeostasis are not well understood.

OBJECTIVE

We used mathematical modelling to further examine mechanisms that exist in the HPT axis regulation for protecting circulating FT3 levels.

METHODS

A mathematical model consisting of a system of four coupled first-order parameterized non-linear ordinary differential equations (ODEs) was developed, accounting for the interdependencies between the hormones in the HPT axis regulation. While TRH and TSH feed forward to the pituitary and thyroid, respectively, FT4 and FT3 feed backward to both the pituitary and hypothalamus. Stable equilibrium solutions of the ODE system express homeostasis for a particular variable, such as FT3, if this variable stays in a narrow range while certain other parameter(s) and system variable(s) may vary substantially.

RESULTS

The model predicts that (1) TSH-feedforward protects FT3 levels if the FT4 production rate declines and (2) combined negative feedback by FT4 and FT3 on both TSH and TRH production rates keeps FT3 levels insensitive to moderate changes in FT4 production rates and FT4 levels. The optimum FT4 and FT3 feedback and TRH and TSH-feedforward ranges that preserve FT3 homeostasis were found by numerical continuation analysis. Model predictions were in close agreement with clinical studies and individual patient examples of hypothyroidism and hyperthyroidism.

CONCLUSIONS

These findings further extend the concept of HPT axis regulation beyond TSH and FT4 to integrate the more active sister hormone FT3 and mechanisms of FT3 homeostasis. Disruption of homeostatic mechanisms leads to disease. This provides a perspective for novel testable concepts in clinical studies to therapeutically target the disruptive mechanisms.

Refining personalized diagnosis, treatment and exploitation of hypothyroidism related to solid nonthyroid cancer

Hypothyroidism in the setting of cancer is a puzzling entity due to the dual role of the thyroid hormones (TH) in cancer – promoting versus inhibitory – and the complexity of the hypothyroidism itself. The present review provides a comprehensive overview of the personalized approach to hypothyroidism in patients with solid nonthyroid cancer, focusing on current challenges, unmet needs and future perspectives. Major electronic databases were searched from January 2011 until March 2022. The milestones of the refinement of such a personalized approach are prompt diagnosis, proper TH replacement and development of interventions and/or pharmaceutical agents to exploit hypothyroidism or, on the contrary, TH replacement as an anticancer strategy. Further elucidation of the dual role of TH in cancer – especially of the interference of TH signaling with the hallmarks of cancer – is anticipated to inform decision-making and optimize patient selection.

Self-reported medication information needs among medication users in a general population aged 40 years and above - the Tromsø study

PURPOSE

To determine the prevalence and associated factors of self-reported medication information needs among medication users in a general population aged 40 years and above - The Tromsø Study.

METHODS

Cross-sectional study of medication users (n = 10,231) among participants in the Tromsø Study, a descriptive analysis of questionnaire data and multivariable logistic regression (n = 9,194).

RESULTS

Sixteen percent of medication users expressed a need for more information about own medications. Overall, medication users agreed to a higher degree to have received information from the GP compared to the pharmacy. Concerned medication users and those disagreeing to have received information about side effects had the highest odds for needing more information (OR 5.07, 95% CI 4.43-5.81) and (OR 2.21, 95% CI 1.83-2.68), respectively. Medication users who used heart medications (e.g., nitroglycerin, antiarrhythmics, anticoagulants) (OR 1.71, 95% CI 1.46-2.01), medication for hypothyroidism (OR 1.36, 95% CI 1.13-1.64) or had moderately health anxiety had expressed need for medication information. Whereas medication users with lower education, those that never used internet to search for health advice, and medication users who disagreed to have received information about reason-for-use were associated with lower odds (OR 0.75, 95% CI 0.62-0.91), (OR 0.85, 95% CI 0.74-0.98) and (OR 0.68, 95% CI 0.53-0.88), respectively.

CONCLUSION

This study demonstrated that there is need for more information about own medications in a general population aged 40 years and above and shed light on several characteristics of medication users with expressed information need which is important when tailoring the right information to the right person.

Minor perturbations of thyroid homeostasis and major cardiovascular endpoints—Physiological mechanisms and clinical evidence

It is well established that thyroid dysfunction is linked to an increased risk of cardiovascular morbidity and mortality. The pleiotropic action of thyroid hormones strongly impacts the cardiovascular system and affects both the generation of the normal heart rhythm and arrhythmia. A meta-analysis of published evidence suggests a positive association of FT4 concentration with major adverse cardiovascular end points (MACE), but this association only partially extends to TSH. The risk for cardiovascular death is increased in both subclinical hypothyroidism and subclinical thyrotoxicosis. Several published studies found associations of TSH and FT4 concentrations, respectively, with major cardiovascular endpoints. Both reduced and elevated TSH concentrations predict the cardiovascular risk, and this association extends to TSH gradients within the reference range. Likewise, increased FT4 concentrations, but high-normal FT4 within its reference range as well, herald a poor outcome. These observations translate to a monotonic and sensitive effect of FT4 and a U-shaped relationship between TSH and cardiovascular risk. Up to now, the pathophysiological mechanism of this complex pattern of association is poorly understood. Integrating the available evidence suggests a dual etiology of elevated FT4 concentration, comprising both ensuing primary hypothyroidism and a raised set point of thyroid function, e. g. in the context of psychiatric disease, chronic stress and type 2 allostatic load. Addressing the association between thyroid homeostasis and cardiovascular diseases from a systems perspective could pave the way to new directions of research and a more personalized approach to the treatment of patients with cardiovascular risk.

Optimized Replacement T4 and T4+T3 Dosing in Male and Female Hypothyroid Patients With Different BMIs Using a Personalized Mechanistic Model of Thyroid Hormone Regulation Dynamics

OBJECTIVE

A personalized simulation tool, p-THYROSIM, was developed (1) to better optimize replacement LT4 and LT4+LT3 dosing for hypothyroid patients, based on individual hormone levels, BMIs, and gender; and (2) to better understand how gender and BMI impact thyroid dynamical regulation over time in these patients.

METHODS

p-THYROSIM was developed by (1) modifying and refining THYROSIM, an established physiologically based mechanistic model of the system regulating serum T3, T4, and TSH level dynamics; (2) incorporating sex and BMI of individual patients into the model; and (3) quantifying it with 3 experimental datasets and validating it with a fourth containing data from distinct male and female patients across a wide range of BMIs. For validation, we compared our optimized predictions with previously published results on optimized LT4 monotherapies. We also optimized combination T3+T4 dosing and computed unmeasured residual thyroid function (RTF) across a wide range of BMIs from male and female patient data.

RESULTS

Compared with 3 other dosing methods, the accuracy of p-THYROSIM optimized dosages for LT4 monotherapy was better overall (53% vs. 44%, 43%, and 38%) and for extreme BMI patients (63% vs. ~51% low BMI, 48% vs. ~36% and 22% for high BMI). Optimal dosing for combination LT4+LT3 therapy and unmeasured RTFs was predictively computed with p-THYROSIM for male and female patients in low, normal, and high BMI ranges, yielding daily T3 doses of 5 to 7.5 μg of LT3 combined with 62.5-100 μg of LT4 for women or 75-125 μg of LT4 for men. Also, graphs of steady-state serum T3, T4, and TSH concentrations vs. RTF (range 0%-50%) for untreated patients showed that neither BMI nor gender had any effect on RTF predictions for our patient cohort data. Notably, the graphs provide a means for estimating unmeasurable RTFs for individual patients from their hormone measurements before treatment.

CONCLUSIONS

p-THYROSIM can provide accurate monotherapies for male and female hypothyroid patients, personalized with their BMIs. Where combination therapy is warranted, our results predict that not much LT3 is needed in addition to LT4 to restore euthyroid levels, suggesting opportunities for further research exploring combination therapy with lower T3 doses and slow-releasing T3 formulations.

Levothyroxine Treatment and the Risk of Cardiac Arrhythmias - Focus on the Patient Submitted to Thyroid Surgery

Levothyroxine (LT4) is used to treat frequently encountered endocrinopathies such as thyroid diseases. It is regularly used in clinical (overt) hypothyroidism cases and subclinical (latent) hypothyroidism cases in the last decade. Suppressive LT4 therapy is also part of the medical regimen used to manage thyroid malignancies after a thyroidectomy. LT4 treatment possesses dual effects: substituting new-onset thyroid hormone deficiency and suppressing the local and distant malignancy spreading in cancer. It is the practice to administer LT4 in less-than-high suppressive doses for growth control of thyroid nodules and goiter, even in patients with preserved thyroid function. Despite its approved safety for clinical use, LT4 can sometimes induce side-effects, more often recorded with patients under treatment with LT4 suppressive doses than in unintentionally LT4-overdosed patients. Cardiac arrhythmias and the deterioration of osteoporosis are the most frequently documented side-effects of LT4 therapy. It also lowers the threshold for the onset or aggravation of cardiac arrhythmias for patients with pre-existing heart diseases. To improve the quality of life in LT4-substituted patients, clinicians often prescribe higher doses of LT4 to reach low normal TSH levels to achieve cellular euthyroidism. In such circumstances, the risk of cardiac arrhythmias, particularly atrial fibrillation, increases, and the combined use of LT4 and triiodothyronine further complicates such risk. This review summarizes the relevant available data related to LT4 suppressive treatment and the associated risk of cardiac arrhythmia.

Efficacy and safety of Barg-e-Sahajna (Moringa oleifera Lam.) in primary hypothyroidism

OBJECTIVES

Hypothyroidism is the most common disorder arising from hormone deficiency. It frequently affects women than men. The prevalence of overall hypothyroidism has been reported to be 4.8-11%. Levothyroxine is the treatment of choice for all types of hypothyroidism. The purpose of this pilot study was to evaluate the efficacy and safety of Barg-e-Sahajna (Leaves of Moringa oleifera Lam.) among diagnosed patients of primary hypothyroidism.

METHODS

This study was an open observational study. A total of 22 patients were screened, out of which 10 were excluded (did not meet inclusion criteria) and 2 refused to consent to be part of the study, rest 10 participants were enrolled after obtaining written informed consent finally 8 subjects completed the study and 2 are dropout in last follow up. The drug was given in the form of decoction at the dose of 5 g fresh leaves twice a day after meal for 45 days.

RESULTS

The study effects on objective parameter thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) were found extremely significant when compared before (16.62 ± 11.49, 132 ± 19.32, 9.28 ± 1.46) and after (4.75 ± 3.12, 150.37 ± 20.68, 11.84 ± 3.81) treatment with a significant decrease in serum TSH level (p<0.0246) and an increase in serum T3 (p<0.0005) and T4 (p<0.0438) levels. The results were analyzed using paired "t" test.

CONCLUSIONS

The improvements in thyroid profiles (TSH, T3 and T4) after consuming 'Barg-e-Sahajna' show that the test drug is effective in primary hypothyroidism and the relief was considerable. No significant effect on safety parameters (serum-glutamic-oxaloacetic-transaminase [SGOT], serum glutamic-pyruvic transaminase [SGPT], blood urea, and serum creatinine) was observed. Therefore, it may be concluded that the Barg-e-Sahajna is preliminarily safe and effective in the management of primary hypothyroidism.

Efficacy and safety of Barg-e-Sahajna (Moringa olifera Lam.) in primary hypothyroidism

OBJECTIVES

Hypothyroidism is the most common disorder arising from hormone deficiency. It frequently affects women than men. The prevalence of overall hypothyroidism has been reported to be 4.8-11%. Levothyroxine is the treatment of choice for all types of hypothyroidism. The purpose of this pilot study was to evaluate the efficacy and safety of Barg-e-Sahajna (Leaves of Moringa olifera Lam.) among diagnosed patients of primary hypothyroidism.

METHODS

This study was an open observational study. A total of 22 patients were screened, out of which 10 were excluded (did not meet inclusion criteria) and 2 refused to consent to be part of the study, rest 10 participants were enrolled after obtaining written informed consent finally 8 subjects completed the study and 2 are dropout in last follow up. The drug was given in the form of decoction at the dose of 5 g fresh leaves twice a day after meal for 45 days.

RESULTS

The study effects on objective parameter thyroid stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) were found extremely significant when compared before (16.62 ± 11.49, 132 ± 19.32, 9.28 ± 1.46) and after (4.75 ± 3.12, 150.37 ± 20.68, 11.84 ± 3.81) treatment with a significant decrease in serum TSH level (p<0.0246) and an increase in serum T3 (p<0.0005) and T4 (p<0.0438) levels. The results were analyzed using paired "t" test.

CONCLUSIONS

The improvements in thyroid profiles (TSH, T3 and T4) after consuming 'Barg-e-Sahajna' show that the test drug is effective in primary hypothyroidism and the relief was considerable. No significant effect on safety parameters (serum-glutamic-oxaloacetic-transaminase [SGOT], serum glutamic-pyruvic transaminase [SGPT], blood urea, and serum creatinine) was observed. Therefore, it may be concluded that the Barg-e-Sahajna is preliminarily safe and effective in the management of primary hypothyroidism.

Theory: Treatments for Prolonged ICU Patients May Provide New Therapeutic Avenues for Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS)

We here provide an overview of treatment trials for prolonged intensive care unit (ICU) patients and theorize about their relevance for potential treatment of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). Specifically, these treatment trials generally target: (a) the correction of suppressed endocrine axes, notably through a "reactivation" of the pituitary gland's pulsatile secretion of tropic hormones, or (b) the interruption of the "vicious circle" between inflammation, oxidative and nitrosative stress (O&NS), and low thyroid hormone function. There are significant parallels in the treatment trials for prolonged critical illness and ME/CFS; this is consistent with the hypothesis of an overlap in the mechanisms that prevent recovery in both conditions. Early successes in the simultaneous reactivation of pulsatile pituitary secretions in ICU patients-and the resulting positive metabolic effects-could indicate an avenue for treating ME/CFS. The therapeutic effects of thyroid hormones-including in mitigating O&NS and inflammation and in stimulating the adreno-cortical axis-also merit further studies. Collaborative research projects should further investigate the lessons from treatment trials for prolonged critical illness for solving ME/CFS.

Sudden Cardiac Arrest in a Patient With Myxedema Coma and COVID-19

SARS-CoV-2 infection is associated with significant lung and cardiac morbidity but there is a limited understanding of the endocrine manifestations of coronavirus disease 2019 (COVID-19). Although thyrotoxicosis due to subacute thyroiditis has been reported in COVID-19, it is unknown whether SARS-CoV-2 infection can also lead to decompensated hypothyroidism. We present the first case of myxedema coma (MC) in COVID-19 and we discuss how SARS-CoV-2 may have precipitated multiorgan damage and sudden cardiac arrest in our patient. A 69-year-old woman with a history of small cell lung cancer presented with hypothermia, hypotension, decreased respiratory rate, and a Glasgow Coma Scale score of 5. The patient was intubated and administered vasopressors. Laboratory investigation showed elevated thyrotropin, very low free thyroxine, elevated thyroid peroxidase antibody, and markedly elevated inflammatory markers. SARS-CoV-2 test was positive. Computed tomography showed pulmonary embolism and peripheral ground-glass opacities in the lungs. The patient was diagnosed with myxedema coma with concomitant COVID-19. While treatment with intravenous hydrocortisone and levothyroxine were begun the patient developed a junctional escape rhythm. Eight minutes later, the patient became pulseless and was eventually resuscitated. Echocardiogram following the arrest showed evidence of right heart dysfunction. She died 2 days later of multiorgan failure. This is the first report of SARS-CoV-2 infection with MC. Sudden cardiac arrest likely resulted from the presence of viral pneumonia, cardiac arrhythmia, pulmonary emboli, and MC-all of which were associated with the patient's SARS-CoV-2 infection.

LT4 and Slow Release T3 Combination: Optimum Therapy for Hypothyroidism?

CONTEXT

Levothyroxine (LT4) is recommended as replacement therapy for thyroid hormone deficiency. However, some hypothyroid patients receiving LT4 therapy do not feel as well as healthy subjects. This article aimed to review current knowledge regarding LT4 monotherapy versus LT4+LT3 combination therapy and propose future directions regarding LT4+slow release T3 combination treatment for hypothyroidism.

EVIDENCE ACQUISITION

We searched PubMed and Scopus using related keywords.

RESULTS

The LT4 monotherapy causes higher serum free T4 (fT4), subnormal serum free T3 (fT3), and fT3/fT4 ratio in one-fourth of patients. The LT4+LT3 combination therapy increases serum T3 and fT3 concentrations and may normalize the fT3/fT4 ratio. However, the primary outcomes, including thyroid hormone deficiency, anxiety, depression, and quality of life, may not be better in LT4+LT3 combination therapy than in LT4 monotherapy. Recent surveys show that combination therapy is on the rise, in particular, due to patient demand. The LT4 plus slow-release LT3 preparation has shown promising results in improving serum thyroid hormone concentrations.

CONCLUSIONS

The beneficial effect of LT4+LT3 combination therapy is not clear, and the safety of long-term therapy is yet under question. More scientific well-designed research projects are required in this field.

Heterogenous biochemical expression of hormone activity in subclinical/overt hyperthyroidism and exogenous thyrotoxicosis

Background

Subclinical hyperthyroidism/thyrotoxicosis originates from different causes and clinical conditions, sharing the laboratory constellation of a suppressed TSH in the presence of thyroid hormone concentrations within the reference range.

Aim

Presentation of hyperthyroidism can manifest itself in several ways. We questioned whether there is either a consistent biochemical equivalence of thyroid hormone response to these diagnostic categories, or a high degree of heterogeneity may exist both within and between the different clinical manifestations.

Methods

This secondary analysis of a former prospective cross-sectional trial involved 461 patients with untreated thyroid autonomy, Graves’ disease or on levothyroxine (LT4) after thyroidectomy for thyroid carcinoma. TSH response and biochemical equilibria between TSH and thyroid hormones were contrasted between endogenous hyperthyroidism and thyrotoxicosis (LT4 overdose).

Results

Concentrations of FT4, FT3, TSH, deiodinase activity and BMI differed by diagnostic category. Over various TSH strata, FT4 concentrations were significantly higher in LT4-treated thyroid carcinoma patients, compared to the untreated diseases, though FT3 levels remained comparable. They were concentrated in the upper FT4- but low deiodinase range, distinguishing them from patients with thyroid autonomy and Graves’ disease. In exogenous thyrotoxicosis, TSH and FT3 were less responsive to FT4 concentrations approaching its upper normal/hyperthyroid range.

Conclusions

The presence or lack of TSH feedforward activity determines the system response in the thyroid-active (hyperthyroidism) and no-thyroid response to treatment (thyrotoxicosis). This rules out a consistent thread of thyroid hormone response running through the different diagnostic categories. TSH measurements should therefore be interpreted conditionally and differently in subclinical hyperthyroidism and thyrotoxicosis.

Functional and Symptomatic Individuality in the Response to Levothyroxine Treatment

Background: For significant numbers of patients dissatisfied on standard levothyroxine (LT4) treatment for hypothyroidism, patient-specific responses to T4 could play a significant role. Aim: To assess response heterogeneity to LT4 treatment, identifying confounders and hidden clusters within a patient panel, we performed a secondary analysis using data from a prospective cross-sectional and retrospective longitudinal study. Methods: Multivariate and multivariable linear models adjusted for covariates (gender, age, and BMI) were stratified by disease-specific treatment indication. During follow-up, pooled observations were compared from the same patient presenting either with or without self-reported symptoms. Statistical analysis was extended to multilevel models to derive intra-class correlation coefficients and reliability measures during follow-up. Results: Equilibria between TSH, FT4, and FT3 serum concentrations in 342 patients were examined by treatment indication (benign goiter, autoimmune thyroiditis, thyroid carcinoma), consequently displaying complex interactive response patterns. Seventy-seven patients treated with LT4 and monitored for thyroid carcinoma presented, in association with changes in LT4 dose, either with hypothyroid symptoms or symptom-free. Significant biochemical differences appeared between the different presentations. Leveled trajectories by subject to relief from hypothyroid symptoms differed significantly, indicating distinct responses, and denying a single shared outcome. These were formally defined by a high coefficient of the intraclass correlation (ICC1, exceeding 0.60 in all thyroid parameters) during follow-up on multiple visits at the same LT4 dose, when lacking symptoms. The intra-personal clusters were clearly differentiated from random variability by random group resampling. Symptomatic change in these patients was strongly associated with serum FT3, but not with FT4 or TSH concentrations. In 25 patients transitioning from asymptomatic to symptomatically hyperthyroid, FT3 concentrations remained within the reference limits, whilst at the same time marked biochemical differences were apparent between the presentations. Conclusions: Considerable intra-individual clustering occurred in the biochemical and symptomatic responses to LT4 treatment, implying statistically multileveled response groups. Unmasking individual differences in the averaged treatment response hereby highlights clinically distinguishable subgroups within an indiscriminate patient panel. This, through well-designed larger clinical trials will better target the different therapeutic needs of individual patients.