Recombinant human thyrotropin is a potent stimulator of thyroid function in normal subjects

Lipidomic Perturbations in Cynomolgus Monkeys are Regulated by Thyroid Stimulating Hormone

Thyroid disease affects an estimated 200 million people worldwide, and is commonly associated with increased blood lipid levels. However, the mechanism by which thyroid-stimulating hormone (TSH) affects lipid profiles is not clear. Twenty-four cynomolgus monkeys were treated with a novel exogenous recombinant human TSH (rhTSH) (SNA001) at 9 μg kg⁻¹, 22 μg kg⁻¹, or 54 μg kg⁻¹, and reference rhTSH (Thyrogen^®) at 22 μg kg⁻¹. The primary TSH (SNA001) pharmacokinetic (PK) parameters increased in a dose-dependent manner across the dose range of 9 μg kg⁻¹, 22 μg kg⁻¹, or 54 μg kg⁻¹. Peak triiodothyronine (T3) and thyroxine (T4) levels were reached within 24 h after rhTSH administration, which was delayed by approximately 20 h. In total, 420 lipid species were detected and quantified by ultra-performance liquid chromatography high resolution spectrometry (UPLC-HR-MS)-based lipidomics. Notably, peak levels of lipid accumulation, particularly sphingomyelin (SM) and triglycerides (TG), appeared at 4 and 24 h, which was consistent with the pattern of TSH and T3/T4 levels, respectively. According to weighted correlation network analysis (WGCNA), perturbations of many lipid species were strongly correlated with TSH and T3/T4 levels. TSH and the stimulated T3/T4 levels and lipid profiles following SNA001 administration were comparable to those after administration of the reference rhTSH (Thyrogen^®). The plasma lipidome and changes in lipid levels after rhTSH stimulation were associated with TSH and T3/T4 concentrations. T3/T4 and lipid profiles were delayed after TSH stimulation. Such phenomena require further exploration.

Familial Longevity is Associated with an Attenuated Thyroidal Response to Recombinant Human Thyroid Stimulating Hormone

CONTEXT

Longevity is associated with higher circulating levels of TSH in the absence of differences in circulating thyroid hormones (TH), as previously observed in F2 members of long-lived families (F2-LLS) and their partners (F2-Con). The mechanism underlying this observed difference remains unknown.

OBJECTIVE

We hypothesized that the thyroid gland of members from long-lived families are less responsive to TSH stimulation, thereby requiring higher circulating TSH levels to maintain adequate TH levels.

METHODS

We performed a case-control intervention study with a single intramuscular (gluteal) injection with 0.1 mg recombinant human TSH in a subgroup of 14 F2-LLS and 15 similarly aged F2-Con. They were followed for 4 days. No serious adverse events were reported. For analyses, we compared time trajectories of TSH and TH, and the ratio of TH to TSH using area under the curve (AUC) calculations.

RESULTS

The AUC free T4/AUC TSH ratio was significantly lower in F2-LLS than in F2-Con (estimated mean [95% confidence interval] 1.6 [1.2-1.9] and 2.2 [1.9-2.6], respectively, P = 0.01). The AUC thyroglobulin/AUC TSH ratio was also lower in F2-LLS than in F2-Con (median [interquartile range] 2.1 [1.4-3.6] and 3.2 [2.7-7.4], respectively, P = 0.04). We observed the same trend with the AUC free T3/AUC TSH ratio, although the difference was not statistically significant (estimated mean [95% confidence interval] 0.6 [0.4-0.7] and 0.7 [0.6-0.8], respectively, P = 0.07).

CONCLUSIONS

The present findings show that members of long-living families have a lower thyroid responsivity to TSH compared with their partners.

Quantitative Measurement of the Thyroid Uptake Function of Mouse by Cerenkov Luminescence Imaging

Cerenkov luminescence imaging (CLI) has been an evolutional and alternative approach of nuclear imaging in basic research. This study aimed to measure the ¹³¹I thyroid uptake of mouse using CLI for assessment of thyroid function. Quantification of ¹³¹I thyroid uptake of mice in euthyroid, hypothyroid and hyperthyroid status was performed by CLI and γ-scintigraphy at 24 hours after injection of ¹³¹I. The ¹³¹I thyroid uptake was calculated using the equation: (thyroid counts − background counts)/(counts of injected dose of ¹³¹I) × 100%. Serum T4 concentration was determined to evaluate the thyroid function. The radioactivity of ¹³¹I was linearly correlated with the CL signals in both in vitro and in vivo measurements. CLI showed a significant decrease and increase of ¹³¹I thyroid uptake in the mice in hypo- and hyperfunctioning status, respectively, and highly correlated with that measured by γ-scintigraphy. However, the percent thyroid uptake measured by CLI were one-fifth of those measured by γ-scintigraphy due to insufficient tissue penetration of CL. These results indicate that CLI, in addition to nuclear imaging, is able to image and evaluate the ¹³¹I thyroid uptake function in mice in preclinical and research settings.

The Relationship between Population T4/TSH Set Point Data and T4/TSH Physiology

Context. Population studies of the distribution of T4/TSH set points suggest a more complex inverse relationship between T4 and TSH than that suggested by physiological studies. The reasons for the similarities and differences between the curves describing these relationships are unresolved. Methods. We subjected the curve, derived from empiric data, describing the TSH suppression response to T4, and the more mathematically derived curve describing the T4 response to TSH, to the different possible models of population variation. The implied consequences of these in terms of generating a population distribution of T4/TSH equilibrium points (a “population curve”) were generated and compared to the empiric population curve. The physiological responses to primary hypothyroidism and hyperthyroidism were incorporated into the analysis. Conclusions. Though the population curve shows a similarly inverse relationship, it is describing a different relationship than the curve describing the suppression of TSH by T4. The population curve is consistent with the physiological studies of the TSH response to T4 and implies a greater interindividual variation in the positive thyroid T4 response to TSH than in the central inhibitory TSH response to T4. The population curve in the dysthyroid states is consistent with known physiological responses to these states.

Exogenous thyrotropin improves renal function in euthyroid patients, while serum creatinine levels are increased in hypothyroidism

Background

There is evidence showing that the hypothyroid state results in increased serum creatinine levels. However, whether this is only due to the peripheral thyroid hormones or if thyroid-stimulating hormone (TSH) is also involved is not known.

Methods

Serum creatinine levels and estimated glomerular filtration rate (eGFR) were assessed in thyroidectomized patients with varying thyroid hormones and TSH levels. Blood samples from Group 1 (21 patients) were obtained 1 month after complete thyroidectomy, while under a hypothyroid state (t1) and a sufficient time after thyroid hormones initiation (euthyroid state, t2). Group 2 (20 euthyroid patients) were sampled after recombinant human thyrotropin injections (rhTSH, t1) and later after rhTSH extinction (t2).

Results

In Group 1, serum creatinine levels decreased after correction of hypothyroidism (85.3 ± 4.3 versus 78.0 ± 3.9 µmol/L; P = 0.04). In Group 2, serum creatinine levels increased after rhTSH withdrawal (70.6 ± 5.7 µmol/L versus 76.5 ± 5.8 µmol/L; P = 0.007). Between t1 and t2, eGFR varied accordingly [Group 1, 71.7 ± 3.5 versus 81.2 ± 4.5 mL/min/1.73 m² (P = 0.02); Group 2, 97.7 ± 7.4 versus 87.5 ± 5.9 (P = 0.007)]. The changes in TSH and eGFR following supplementation with thyroxine were significantly correlated (r = −0.6, P = 0.0041).

Conclusions

Iatrogenic hypothyroidism significantly increases serum creatinine and reversibly impairs eGFR, while treatment with rhTSH enhances renal function in euthyroid patients, supporting the existence of an influence of TSH level on renal function. The mechanisms by which peripheral thyroid hormones and TSH influence GFR need to be identified in physiology-orientated studies.

Inability of recombinant human thyrotropin to predict the evolution from subclinical hypothyroidism to overt disease. A pilot study

BACKGROUND

The use of recombinant human TSH (rhTSH) is indicated to evaluate thyroid carcinoma patients. In recent years, some authors have reported that rhTSH could serve as a dynamic test of thyroid reserve. The aim of the present study was to determine whether or not rhTSH can predict the evolution from subclinical hypothyroidism (SH) to overt hypothyroidism.

MATERIALS AND METHODS

Twenty-one women who met the diagnostic criteria of SH were enrolled. All patients received a single dose of rhTSH (0.1 mg). Basal blood samples for TSH, free T4 (fT4), thyroglobulin (Tg), and anti-thyoperoxidase and anti-Tg antibodies were obtained before and 1 day after rhTSH administration. All patients were followed for 2 yr, and blood samples were obtained every 6 months.

RESULTS

Twenty-four hours after rhTSH administration, the TSH level increased to >20 mU/l in 14 patients; the serum peak TSH levels remained <10 mU/l in only 5 patients. On follow-up, 7 women (33%) required L-T4 replacement therapy for overt hypothyroidism or a persistent TSH level >10 mlU/l. None of the parameters analyzed differed significantly between patients who developed overt hypothyroidism from those who had persistent SH.

CONCLUSIONS

The response of thyroid function tests to a single low dose of rhTSH is not useful in identifying those patients with SH who will develop overt hypothyroidism over a 2-yr period.

Extensions, validation, and clinical applications of a feedback control system simulator of the hypothalamo-pituitary-thyroid axis

BACKGROUND

We upgraded our recent feedback control system (FBCS) simulation model of human thyroid hormone (TH) regulation to include explicit representation of hypothalamic and pituitary dynamics, and updated TH distribution and elimination (D&E) parameters. This new model greatly expands the range of clinical and basic science scenarios explorable by computer simulation.

METHODS

We quantified the model from pharmacokinetic (PK) and physiological human data and validated it comparatively against several independent clinical data sets. We then explored three contemporary clinical issues with the new model: combined triiodothyronine (T(3))/thyroxine (T(4)) versus T(4)-only treatment, parenteral levothyroxine (L-T(4)) administration, and central hypothyroidism.

RESULTS

Combined T(3)/T(4) therapy--In thyroidectomized patients, the L-T(4)-only replacement doses needed to normalize plasma T(3) or average tissue T(3) were 145 microg L-T(4)/day or 165 microg L-T(4)/day, respectively. The combined T(4) + T(3) dosing needed to normalize both plasma and tissue T(3) levels was 105 microg L-T(4) + 9 microg T(3) per day. For all three regimens, simulated mean steady-state plasma thyroid-stimulating hormone (TSH), T(3), and T(4) was within normal ranges (TSH: 0.5-5 mU/L; T(4): 5-12 microg/dL; T(3): 0.8-1.9 ng/mL). Parenteral T(4) administration--800 microg weekly or 400 microg twice weekly normalized average tissue T(3) levels both for subcutaneous (SC) and intramuscular (IM) routes of administration. TSH, T(3), and T(4) levels were maintained within normal ranges for all four of these dosing schemes (1x vs. 2x weekly, SC vs. IM). Central hypothyroidism--We simulated steady-state plasma T(3), T(4), and TSH concentrations in response to varying degrees of central hypothyroidism, reducing TSH secretion from 50% down to 0.1% of normal. Surprisingly, TSH, T(3), and T(4) plasma concentrations remained within normal ranges for TSH secretion as low as 25% of normal.

CONCLUSIONS

Combined T(3)/T(4) treatment--Simulated standard L-T(4)-only therapy was sufficient to renormalize average tissue T(3) levels and maintain normal TSH, T(3), and T(4) plasma levels, supporting adequacy of standard L-T(4)-only treatment. Parenteral T(4) administration-TSH, T(3), and T(4) levels were maintained within normal ranges for all four of these dosing schemes (1x vs. 2x weekly, SC vs. IM), supporting these therapeutic alternatives for patients with compromised L-T(4) gut absorption. Central hypothyroidism--These results highlight how highly nonlinear feedback in the hypothalamic-pituitary-thyroid axis acts to maintain normal hormone levels, even with severely reduced TSH secretion.

Newly reported roles of thyroid-stimulating hormone and follicle-stimulating hormone in bone remodelling

Thyroid-stimulating hormone (TSH) and follicle-stimulating hormone (FSH) have both been recently implicated in bone remodelling. Clinical evidence, as well as data from TSH receptor and thyroid hormone receptor knockout mice, suggest that TSH has a direct effect on skeletal homeostasis, although some data are conflicting. Recently, the exogenous administration of TSH has been shown to positively impact bone in oophrectomised rats. These data, along with their potential implications for the treatment of severe osteoporosis, are discussed.