The Use of TSH in Determining Thyroid Disease: How Does It Impact the Practice of Medicine in Pregnancy?

Assessment of Dietary Supplementation of Lactobacillus rhamnosus Probiotic on Growth Performance and Disease Resistance in Oreochromis niloticus

Probiotics play a significant role in aquaculture by improving the growth, health, and survival rate of fish against pathogenic organisms. In the present study, we have evaluated the effects of a Lactobacillus rhamnosus (L. rhamnosus) probiotic on growth performance and disease resistance in Oreochromis niloticus (O. niloticus) fingerlings. Four different concentrations of L. rhamnosus (T1: 0.5 × 10¹⁰, T2: 1 × 10¹⁰, T3: 1.5 × 10¹⁰, and T4: 2 × 10¹⁰ CFU/kg feed) were administered to fish over a period of three months. L. rhamnosus treated fish revealed a high growth increment as compared to the control, and the values of macromolecules (amino acids, fatty acids, and carbohydrates) varied significantly among the treated and control groups. Levels of thyroid hormones were noted to be high in the probiotic-treated groups. A challenge assay was performed with Aeromonas hydrophila (A. hydrophila). The optimum calculated concentration of probiotics from the growth assay (1.5 × 10¹⁰ CFU/kg feed) was used for the challenge assay. Fish were divided into four groups as follows: control (Con), probiotic-treated (PL), infected (I), and infected + probiotic-treated (I + PL) groups. Significant variations in hematological parameters were observed among control and treated groups. Histopathological changes were recorded in infected fish, while the infected + probiotic-treated group showed less deformations indicating the positive effect of the probiotic supplementation. The survival rate of fish was also better in the probiotic-treated group. Based on these findings, we conclude that probiotic supplementation enhances the growth and improves immunity of O. niloticus. Therefore, we propose that probiotics can be used as promising feed supplements for promoting fish production and disease resistance in aquaculture.

Profiling retrospective thyroid function data in complete thyroidectomy patients to investigate the HPT axis set point (PREDICT-IT)

BACKGROUND

The homeostatic euthyroid set point of the hypothalamus-pituitary-thyroid axis of any given individual is unique and oscillates narrowly within substantially broader normal population ranges of circulating free thyroxine (FT4) and thyroid-stimulating hormone (TSH), otherwise termed 'thyroid function test (TFT)'. We developed a mathematical algorithm codenamed Thyroid-SPOT that effectively reconstructs the personalized set point in open-loop situations and evaluated its performance in a retrospective patient sample.

METHODS

We computed the set points of 101 patients who underwent total thyroidectomy for non-functioning thyroid disease using Thyroid-SPOT on each patient's own serial post-thyroidectomy TFT. Every predicted set point was compared against its respective healthy pre-operative euthyroid TFT per individual and their separation (i.e. predicted-observed TFT) quantified.

RESULTS

Bland-Altman analysis to measure the agreement between each pair of an individual's predicted and actual set points revealed a mean difference in FT4 and TSH of + 3.03 pmol/L (95% CI 2.64, 3.43) and - 0.03 mIU/L (95% CI - 0.25, 0.19), respectively. These differences are small compared to the width of the reference intervals. Thyroid-SPOT can predict the euthyroid set point remarkably well, especially for TSH with a 10-16-fold spread in magnitude between population normal limits.

CONCLUSION

Every individual's equilibrium euthyroid set point is unique. Thyroid-SPOT serves as an accurate, precise and reliable targeting system for optimal personalized restoration of euthyroidism. This algorithm can guide clinicians in L-thyroxine dose titrations to resolve persistent dysthyroid symptoms among challenging cases harbouring "normal TFT" within the laboratory ranges but differing significantly from their actual euthyroid set points.

Assessment of the Thyroid Functions among Female Flight Attendants

Introduction: Epidemiological observations indicate that stewardesses are exposed to reproductive and endocrine system disturbances. The aim of the study was to assess of thyroid function disturbances as well as to identify factors affecting the thyroid function among stewardesses working both within one time zone and on long-distance flights. Material and methods: The cross-sectional study covered 103 women aged 23–46. The study group (I) was divided into two subgroups: group Ia comprising stewardesses flying within one flight zone and group Ib stewardesses working on long-distance flights. The control group (II) were women of reproductive age who sought medical assistance due to marital infertility in whom the male factor was found to be responsible for problems with conception in the course of the diagnostic process. The assessment included: age, BMI, menstrual cycle regularity, length of work, frequency of flying, thyroid stimulating hormone (TSH) concentration, level of free thyroxine (fT4), antibodies to thyroglobulin (aTG) and to thyroperoxidase (aTPO), prolactin concentration, sex hormone binding globulin (SHGB) concentration, total cholesterol, and low density lipoprotein (LDL) fraction. Descriptive methods and inferential statistics methods were used to compile the data. Results: The difference between the concentrations of TSH in the study group (2.59 mcIU/mL) and the control group (1.52 mcIU/mL) was statistically significant (p < 0.01). An elevated titer of thyroid antibodies (aTPO and/or aTG) was revealed in 46.3% of stewardesses and in 15.1% of patients from the control group (p < 0.001). Groups Ia and Ib in individual concentrations were not statistically significant. The frequency of occurrence of an elevated titer of thyroid antibodies depended on the length of work in the study group (p > 0.05). No statistically significant difference was found in patients spending up to 60 h a month flying and in patients spending more than 60 h flying, the percentage of the occurrence of thyroid antibodies was 50% and 43.5, respectively. Conclusions: The occurrence in stewardesses of a higher TSH concentration than in the control group can signify that stewardesses are burdened with a higher risk of the development of hypothyroidism in the future. The character of the work of stewardesses (frequency of flying as well as length of work) does not affect the immunological profile of the thyroid.

Hypothyroidism during pregnancy and its association to perinatal and obstetric morbidity: a review

There is currently no consensus among the different scientific societies on screening for thyroid dysfunction in the first trimester of pregnancy. Indeed, diagnosis and treatment of subclinical hypothyroidism during pregnancy are controversial, as no cut-off value for thyrotropin (TSH) is universally accepted. TSH measurement may be influenced by different factors throughout pregnancy, but especially during the first trimester. The association between overt hypothyroidism during pregnancy and obstetric and perinatal complications is well established. It is also accepted that thyroid hormones are important for neurodevelopment of the offspring. However, there is no scientific evidence available about the impact of subclinical hypothyroidism and its treatment during the first trimester of pregnancy on children's neurodevelopment. In recent years, studies conducted in the offspring of mothers with subclinical hypothyroidism have reported new biochemical parameters which may eventually serve as biomarkers of offspring neurodevelopment and which are more reproducible and are measured at an earlier time than the conventional clinical tests.

Thyroid dysfunction in the era of precision medicine

The launching of the Precision Medicine Initiative by the President of the United States in January 2015 was an invitation for all healthcare professionals to review their practice. This call should stimulate thyroidologists working in different areas (from basic research or epidemiology to the frontline of the clinical arena or to those designing public health programs) to be aware of this new outlook. The aim of the initiative is to eradicate imprecision in estimating the probability of a correct diagnosis, to be as sure as possible of the most effective treatment, and to maximize the chances of a successful outcome. This paper summarizes some of the current challenges faced by endocrinologists in the field of thyroid dysfunction, and illustrates how precision medicine may improve diagnosis and therapy in the future.

Subclinical Hypothyroidism and Thyroid Autoimmunity Are Not Associated With Fecundity, Pregnancy Loss, or Live Birth

CONTEXT

Prior studies examining associations between subclinical hypothyroidism and antithyroid antibodies with early pregnancy loss and live birth suggest mixed results and time to pregnancy (TTP) has not been studied in this patient population.

OBJECTIVE

This study sought to examine associations of prepregnancy TSH concentrations and thyroid autoimmunity with TTP, pregnancy loss, and live birth among women with proven fecundity and a history of pregnancy loss.

DESIGN AND SETTING

This was a prospective cohort study from a large, randomized controlled trial that took place at four medical centers in the United States.

PATIENTS OR OTHER PARTICIPANTS

Healthy women, ages 18-40 y, who were actively attempting to conceive and had one or two prior pregnancy losses and no history of infertility were eligible for the study.

INTERVENTION

There were no interventions.

MAIN OUTCOME MEASURE

TTP, pregnancy loss, and live birth.

RESULTS

Women with TSH ≥ 2.5 mIU/L did not have an increased risk of pregnancy loss (risk ratio, 1.07; 95% confidence interval [CI], 0.81-1.41) or a decrease in live birth rate (risk ratio, 0.97; 95% CI, 0.88-1.07) or TTP (fecundability odds ratio, 1.09; 95% CI, 0.90-1.31) compared with women with TSH <2.5 mIU/L after adjustment for age and body mass index. Similar findings were observed for women with thyroid autoimmunity and after additional adjustment for treatment assignment.

CONCLUSIONS

Among healthy fecund women with a history pregnancy loss, TSH levels ≥ 2.5 mIU/L or the presence of antithyroid antibodies were not associated with fecundity, pregnancy loss, or live birth. Thus, women with subclinical hypothyroidism or thyroid autoimmunity can be reassured that their chances of conceiving and achieving a live birth are likely unaffected by marginal thyroid dysfunction.

THE LONG-TERM IMPACT OF CONTROLLED OVARIAN HYPERSTIMULATION ON THYROID FUNCTION

OBJECTIVE

Evidence on the long-term impact of controlled ovarian hyperstimulation (COH) on thyroid function is scarce. To investigate this, we report on serum thyroid-stimulating hormone (TSH) modifications in euthyroid and hypothyroid women during COH and 3 months after the end of the stimulation cycle.

METHODS

Women who underwent in vitro fertilization (IVF) and who did not become pregnant were eligible. Cases were women with treated hypothyroidism and basal serum TSH <2.5 mIU/L. Controls were euthyroid women matched to cases by age and basal serum TSH. Women could be included if serum TSH was available at 4 time points: prior to initiating COH (time 1); at the time of human chorionic gonadotropin (hCG) administration (time 2); 16 days after hCG administration (time 3); and 3 months after the end of the IVF cycle (time 4).

RESULTS

Thirty-seven case-control pairs were included. Serum TSH at times 1, 2, 3, and 4 was 1.7 ± 0.6, 3.1 ± 1.4, 3.1 ± 1.3, and 2.7 ± 1.7 mIU/L, and 1.7 ± 0.6, 2.9 ± 1.0, 2.7 ± 1.0, and 1.9 ± 0.7 mIU/L among cases and controls, respectively. A statistically significant difference emerged at time 4 (P<.001). In both groups, serum TSH was higher at time 4 compared to time 1. Serum TSH exceeded the recommended threshold of 2.5 mIU/L at time 4 in 51% of cases (95% confidence interval [CI], 35 to 68%) and in 16% of controls (95% CI, 4 to 28%) (P = .003).

CONCLUSION

COH seems to have a long-term impact on TSH levels. The magnitude of this effect is particularly pronounced in hypothyroid women.

Thyroid axis dysregulation during in vitro fertilization in hypothyroid-treated patients

BACKGROUND

While there is a large body of evidence showing a significant impact of controlled ovarian hyperstimulation (COH) on thyroid function in euthyroid patients undergoing in vitro fertilization (IVF), information on the effect of this treatment on thyroid axis equilibrium in hypothyroid-treated patients is insufficient. The goal of this prospective study was to investigate serum thyroid-stimulating hormone (TSH) modifications in hypothyroid-treated patients during IVF.

METHODS

Hypothyroid-treated women selected for IVF between November 2010 and December 2011 were considered for study entry. They were eligible if serum TSH tested the month preceding the IVF cycle was 0.4-2.5 mIU/L. Additional inclusion criteria were as follows: (1) a certified diagnosis of clinical or subclinical hypothyroidism; (2) consumption of at least 25 μg of levothyroxine daily; (3) serum free triiodothyronine and free thyroxine tested the month preceding the IVF cycle within the reference range; (4) no previous IVF cycles; (5) regular menstrual cycles; and (6) day 3 serum follicle-stimulating hormone <12 IU/mL and anti-Müllerian hormone >0.5 ng/mL. Serum TSH was tested at three time points: between day 1 and day 8 of the cycle during the month preceding the start of controlled ovarian hyperstimulation (COH), at the time of human chorionic gonadotropin (hCG) administration and at 16 days after hCG administration.

RESULTS

Seventy-two women met our selection criteria. The serum levels of TSH at basal assessment, at the time of hCG administration, and at 16 days after hCG administration were 1.7 ± 0.7, 2.9 ± 1.3, and 3.2 ± 1.7 mIU/L, respectively. All pairwise comparisons were statistically significant. Serum TSH exceeded the threshold of 2.5 mIU/L in 46 subjects at the time of hCG administration (64%, [CI: 53-75%]) and in 49 subjects 16 days after hCG administration (68%, [CI: 57-79%]).

CONCLUSIONS

Serum TSH increased considerably during COH in adequately treated hypothyroid women undergoing IVF. We suggest strictly monitoring these women during IVF cycles and, if necessary, promptly adjusting the levothyroxine dose. This is the most pragmatic approach but, to date, it is not supported by clinical evidence. Further studies aimed at clarifying the most suitable therapeutic strategy are thus warranted.

The homeostatic set point of the hypothalamus-pituitary-thyroid axis--maximum curvature theory for personalized euthyroid targets

BACKGROUND

Despite rendering serum free thyroxine (FT4) and thyrotropin (TSH) within the normal population ranges broadly defined as euthyroidism, many patients being treated for hyperthyroidism and hypothyroidism persistently experience subnormal well-being discordant from their pre-disease healthy euthyroid state. This suggests that intra-individual physiological optimal ranges are narrower than laboratory-quoted normal ranges and implies the existence of a homeostatic set point encoded in the hypothalamic-pituitary-thyroid (HPT) axis that is unique to every individual.

METHODS

We have previously shown that the dose-response characteristic of the hypothalamic-pituitary (HP) unit to circulating thyroid hormone levels follows a negative exponential curve. This led to the discovery that the normal reference intervals of TSH and FT4 fall within the 'knee' region of this curve where the maximum curvature of the exponential HP characteristic occurs. Based on this observation, we develop the theoretical framework localizing the position of euthyroid homeostasis over the point of maximum curvature of the HP characteristic.

RESULTS

The euthyroid set points of patients with primary hypothyroidism and hyperthyroidism can be readily derived from their calculated HP curve parameters using the parsimonious mathematical model above. It can be shown that every individual has a euthyroid set point that is unique and often different from other individuals.

CONCLUSIONS

In this treatise, we provide evidence supporting a set point-based approach in tailoring euthyroid targets. Rendering FT4 and TSH within the laboratory normal ranges can be clinically suboptimal if these hormone levels are distant from the individualized euthyroid homeostatic set point. This mathematical technique permits the euthyroid set point to be realistically computed using an algorithm readily implementable for computer-aided calculations to facilitate precise targeted dosing of patients in this modern era of personalized medicine.