Enhancement of vascular endothelial function by recombinant human thyrotropin

Effectiveness Assessment of a Modified Preservation Solution Containing Thyrotropin or Follitropin Based on Biochemical Analysis in Perfundates and Homogenates of Isolated Porcine Kidneys after Static Cold Storage

In this paper, we assess the nephroprotective effects of thyrotropin and follitropin during ischaemia. The studies were performed in vitro in a model of isolated porcine kidneys stored in Biolasol (FZNP, Biochefa, Sosnowiec, Poland) and modified Biolasol (TSH: 1 µg/L; FSH 1 µg/L). We used the static cold storage method. The study was carried out based on 30 kidneys. The kidneys were placed in 500 mL of preservation solution chilled to 4 °C. The samples for biochemical tests were collected during the first kidney perfusion (after 2 h of storage) and during the second perfusion (after 48 h of storage). The results of ALT, AST, and LDH activities confirm the effectiveness of Biolasol + p-TSH in maintaining the structural integrity of renal cell membranes. Significantly reduced biochemical parameters of kidney function, i.e., creatinine and protein concentrations were also observed after 48 h storage. The protective effect of Biasol + p-TSH is most pronounced after 2 h of storage, suggesting a mild course of damage thereafter. A mild deterioration of renal function was observed after 48 h. The results of our analyses did not show any protective effect of Biolasol + p-FSH on the kidneys during ischaemia.

Recombinant Human Thyrotropin Improves Endothelial Coronary Flow Reserve in Thyroidectomized Patients with Differentiated Thyroid Cancer

BACKGROUND

The role of thyrotropin (TSH) on the cardiovascular system has been poorly investigated. It is unknown whether the changes in the vasculature associated with thyroid diseases result from altered thyroid hormone action or whether they are a consequence of a direct effect of TSH on endothelial cells. The present study was designed to evaluate the endothelial response of coronary flow to TSH in patients with differentiated thyroid cancer (DTC) without cardiovascular risk factors.

METHODS

The study population consisted of three men and seven women (M_age = 32.6 ± 8 years) who underwent total thyroidectomy for DTC. All were receiving therapy with L-thyroxine to maintain TSH within the reference range. No patient was obese, or had hypertension, diabetes, or dyslipidemia. Patients underwent standard echo-Doppler examination with evaluation of the coronary flow reserve (CFR) of the distal left anterior descending artery obtained by cold pressure test (CPT) before and 24 h after the second recombinant human TSH (rhTSH) injection.

RESULTS

Left ventricular morphology and systolic and diastolic function were normal in all patients. Levels of thyroid hormones and thyroglobulin and antithyroglobulin antibodies did not differ significantly pre- versus post-rhTSH treatment, whereas TSH levels were higher after rhTSH administration. Blood pressure and heart rate were not affected by rhTSH. Coronary flow peak velocity at rest (22.3 ± 6 vs 23.2 ± 8.7; p = 0.66) did not differ between baseline and 24 h after rhTSH, while post-CPT velocity (29.3 ± 6.8 vs 34.4 ± 10.9; p < 0.05) and the CFR were higher after rhTSH administration (1.32 ± 0.2 vs. 1.53 ± 0.2; p < 0.01).

CONCLUSIONS

rhTSH administration may improve the CFR after the non-pharmacological stressor CPT in DTC patients. The increase of coronary blood flow after rhTSH suggests that TSH may exert a protective effect on the coronary endothelium.

Effect of Thyrotropin on Osteopontin, Integrin αvβ3, and VCAM-1 in the Endothelium via Activation of Akt

Numerous epidemiological studies have shown that subclinical hypothyroidism (SCH) can impair endothelial function and cause dyslipidemia. Studies have evaluated the effects of thyroid stimulating hormone (TSH) on endothelial cells, but the mechanism underlying the proatherosclerotic effect of increased TSH levels remains unclear. In the present study, SCH rat models were established in thyroidectomized Wistar rats that were given l-T₄ daily. The results showed that in vivo, the expression of osteopontin (OPN) vascular cell adhesion molecule (VCAM-1), and levels of integrin α_vβ₃ in the aortic tissue in SCH and Hypothyroidism (CH) groups was higher than in the control group. However, the effect in the SCH group was higher than in the CH group. In vitro, results showed that different concentration and time gradients of TSH stimulation could increase the expression of OPN, VCAM-1, and integrin α_vβ₃, and this was accompanied by extracellular signal regulated kinase 1/2 (Erk1/2) and Akt activation in human umbilical vein endothelial cells (HUVECs). TSH induced elevation of these proatherosclerotic factors was partially suppressed by a specific Akt inhibitor but not by a specific Erk inhibitor. Findings suggested that the endothelial dysfunction caused by SCH was related to increased proatherosclerotic factors induced by TSH via Akt activation.

Endogenous TSH levels at the time of 131I ablation do not influence ablation success, recurrence-free survival or differentiated thyroid cancer-related mortality

PURPOSE

Based on a single older study it is established dogma that TSH levels should be ≥30 mU/l at the time of postoperative ¹³¹I ablation in differentiated thyroid cancer (DTC) patients. We sought to determine whether endogenous TSH levels, i.e. after levothyroxine withdrawal, at the time of ablation influence ablation success rates, recurrence-free survival and DTC-related mortality.

METHODS

A total of 1,873 patients without distant metastases referred for postoperative adjuvant ¹³¹I therapy were retrospectively included from 1991 onwards. Successful ablation was defined as stimulated Tg <1 μg/l.

RESULTS

Age, gender and the presence of lymph node metastases were independent determinants of TSH levels at the time of ablation. TSH levels were not significantly related to ablation success rates (p = 0.34), recurrence-free survival (p = 0.29) or DTC -elated mortality (p = 0.82), but established risk factors such as T-stage, lymph node metastases and age were. Ablation was successful in 230 of 275 patients (83.6 %) with TSH <30 mU/l and in 1,359 of 1,598 patients (85.0 %) with TSH ≥30 mU/l. The difference was not significant (p = 0.55). Of the whole group of 1,873 patients, 21 had recurrent disease. There were no significant differences in recurrence rates between patients with TSH <30 mU/l and TSH ≥30 mU/l (p = 0.16). Ten of the 1,873 patients died of DTC. There were no significant differences in DTC-specific survival between patients with TSH <30 mU/l and TSH ≥30 mU/l (p = 0.53).

CONCLUSION

The precise endogenous TSH levels at the time of ¹³¹I ablation are not related to the ablation success rates, recurrence free survival and DTC related mortality. The established dogma that TSH levels need to be ≥30 mU/l at the time of ¹³¹I ablation can be discarded.

TSH stimulates the proliferation of vascular smooth muscle cells

Subclinical hypothyroidism (SCH) was reported to be associated with atherosclerosis (AS) in recent studies. Thyroid hormone levels are normal in patients with SCH, but the levels of thyroid-stimulating hormone (TSH) are increased. Thyroid-stimulating hormone receptor (TSHR) in extra-thyroidal tissues plays a pathophysiological role in these conditions. Our previous results demonstrated that TSHR was functional in hepatocytes and revealed elevated total cholesterol levels in the serum, which were an independent risk factor for AS. TSHR is expressed in vascular smooth muscle cells (VSMCs), and VSMC proliferation plays an important role in the development of AS. Cell proliferation was measured by the MTT assay. Intracellular cyclic AMP (cAMP) was measured using a cAMP ELISA kit. Cells were analyzed using a flow cytometer to determine the cell-cycle phase of each cell. For the purpose of detecting cyclin A and cyclin D, immunohistochemical staining and western blots were performed. Real-time PCR was used to assess the VSMC phenotypes. TSH increased cell progression into the G2/M phases and induced VSMC proliferation; thus, functional TSHR was present on VSMCs. Furthermore, the expression of cyclin D1 and cyclin A was increased. In addition, the results indicated that VSMCs undergo a phenotypic transformation from a contractile state to a synthetic state after treatment with different concentrations of TSH. Elevated TSH can promote VSMC proliferation through the cAMP-dependent pathway.

Effects of recombinant human thyrotropin administration on 24-hour arterial pressure in female undergoing evaluation for differentiated thyroid cancer

Objective. Thyroid-stimulating-hormone (TSH) receptors are expressed in endothelial cells. We investigated whether elevated TSH levels after acute recombinant TSH (rhTSH) administration may result in alterations in blood pressure (BP) in premenopausal women with well-differentiated thyroid carcinoma (DTC). Designs. Thirty euthyroid DTC female patients were evaluated by rhTSH stimulation test (mean age 40.4 ± 8.6 years). A 24 h ambulatory systolic and diastolic blood pressure (SBP, DBP) monitoring (24 hr ABPM) was performed on days 2-3(D2-3). TSH was measured on day 1(D1), day 3(D3), and day 5(D5). Central blood pressure was evaluated on D3. Twenty-three patients were studied 1-4 weeks earlier (basal measurements). Results. TSH levels were D1: median 0.2 mU/L, D3: median 115.0 mU/L, and D5: median 14.6 mU/L. There were no significant associations between TSH on D1 and D3 and any BP measurements. Median D5 office-SBP and 24 h SBP, DBP, and central SBP were correlated with D5-TSH (P < 0.04). In those where a basal 24 h ABPM had been performed median pulse pressure was higher after rhTSH-test (P = 0.02). Conclusions. TSH, when acutely elevated, may slightly increase SBP, DBP, and central SBP. This agrees with previous reports showing positive associations of BP with TSH.

Radioiodine therapy in benign thyroid diseases: effects, side effects, and factors affecting therapeutic outcome

Radioiodine ((131)I) therapy of benign thyroid diseases was introduced 70 yr ago, and the patients treated since then are probably numbered in the millions. Fifty to 90% of hyperthyroid patients are cured within 1 yr after (131)I therapy. With longer follow-up, permanent hypothyroidism seems inevitable in Graves' disease, whereas this risk is much lower when treating toxic nodular goiter. The side effect causing most concern is the potential induction of ophthalmopathy in predisposed individuals. The response to (131)I therapy is to some extent related to the radiation dose. However, calculation of an exact thyroid dose is error-prone due to imprecise measurement of the (131)I biokinetics, and the importance of internal dosimetric factors, such as the thyroid follicle size, is probably underestimated. Besides these obstacles, several potential confounders interfere with the efficacy of (131)I therapy, and they may even interact mutually and counteract each other. Numerous studies have evaluated the effect of (131)I therapy, but results have been conflicting due to differences in design, sample size, patient selection, and dose calculation. It seems clear that no single factor reliably predicts the outcome from (131)I therapy. The individual radiosensitivity, still poorly defined and impossible to quantify, may be a major determinant of the outcome from (131)I therapy. Above all, the impact of (131)I therapy relies on the iodine-concentrating ability of the thyroid gland. The thyroid (131)I uptake (or retention) can be stimulated in several ways, including dietary iodine restriction and use of lithium. In particular, recombinant human thyrotropin has gained interest because this compound significantly amplifies the effect of (131)I therapy in patients with nontoxic nodular goiter.

Enhanced proatherogenic inflammation after recombinant human TSH administration in patients monitored for thyroid cancer remnant

OBJECTIVE

To evaluate the effect of recombinant human TSH (rhTSH) on biomarkers of vascular endothelial cell and platelet activation in patients monitored for thyroid carcinoma remnant.

METHODS

Circulating levels of soluble(s) intercellular adhesion molecule (sICAM)-1 and sE-selectin, as indices of vascular endothelial cell activation, of sP-selectin and sCD40 ligand (sCD40L), as indices of platelet activation, and of 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)), as an index of lipid peroxidation, were evaluated in 20 patients (16 females, 48.0 +/- 13.6 years) at baseline and after intramuscular rhTSH injection (0.9 mg/day on two consecutive days).

RESULTS

At baseline, serum TSH values were below normal whereas free T3 and free T4 were within the normal range. After rhTSH injection, serum TSH increased significantly but free T3 and free T4 remained unchanged. Concomitantly, plasma sICAM-1 concentrations increased significantly (from 155.9 +/- 39.1 to 183.6 +/- 38.1 ng/ml, P < 0.03), as did those of sE-selectin (from 74.8 +/- 15.4 to 91.4 +/- 12.2 ng/ml, P < 0.0006), sP-selectin (from 56.4 +/- 13.7 to 72.2 +/- 14.9 ng/ml, P < 0.002), sCD40L (from 2.1 +/- 0.9 to 2.8 +/- 1.1 ng/ml, P < 0.03) and total 8-iso-PGF(2alpha)(from 238.5 +/- 47.0 to 307.8 +/- 41.2 pg/l, P < 0.0001). Changes in circulating levels of sCD40L were directly correlated with changes in levels of plasma total 8-iso-PGF(2alpha) (r = 0.523, P < 0.02) and sP-selectin (r = 0.480, P < 0.03).

CONCLUSIONS

Supraphysiological concentrations of rhTSH might exert proatherogenic effects by promoting activation of vascular endothelial cells and platelets probably through enhanced oxidative stress.

Arterial stiffness but not intima-media thickness is increased in euthyroid patients with Hashimoto's thyroiditis: The effect of menopausal status

BACKGROUND

Hashimoto's thyroiditis (HT) is an autoimmune disorder associated with increased cardiovascular risk, mainly as a result of accelerated atherosclerosis. The aim of this study was to determine the effect of HT on carotid atherosclerosis and arterial stiffness, as possible mediators of this vascular impairment. Menopausal status was also considered in this setting since HT is mainly prevalent in women.

METHODS

Fifty-four women with HT and normal thyroid function (thyrotropin [TSH] < 4.5 mU/L) and 72 healthy controls with comparable age and risk factor prevalence were examined in this cross-sectional study. Intima-media thickness (IMT) in the carotid arteries averaged from six sites and carotid-femoral pulse wave velocity (PWV) were measured.

RESULTS

Although both groups had TSH levels within normal limits, TSH was higher in HT patients (2.1 +/- 1.16 vs. 1.5 +/- 0.8 mU/L, p = 0.001). PWV (7.95 +/- 2.02 vs. 7.21 +/- 1.24 m/s, p = 0.021), but not IMT (0.644 +/- 0.144 vs. 0.651 +/- 0.169 mm, p = 0.798), was significantly higher in HT patients compared to controls. When the women were divided according to menopausal status, only premenopausal women without HT had significantly lower PWV when compared with the three other subgroups (6.51 +/- 1.09 m/s premenopausal controls vs. 7.64 +/- 2.05 m/s premenopausal HT vs. 7.69 +/- 1.11 m/s postmenopausal controls vs. 8.3 +/- 1.97 m/s postmenopausal HT, p < 0.001). By multivariate analysis PWV independently correlated with age (p = 0.042), the presence of HT (p = 0.002), TSH (p = 0.003), and menopause (p < 0.001) in the whole population while HT was an independent determinant of PWV only in premenopausal women.

CONCLUSIONS

HT is associated with increased PWV independent of arterial atheromatosis, indicating a direct impact of this disorder on arterial stiffening. This effect may be masked in postmenopausal women possibly due to their heavier cardiovascular risk profile.

Inducible nitric oxide synthase is involved in endothelial dysfunction of mesenteric small arteries from hypothyroid rats

The time-dependent effects of mild hypothyroidism on endothelial function were assessed in rat mesenteric arteries. Male Wistar rats were treated with methimazole (MMI; 0.003%) or placebo up to 16 wk. Endothelial function of mesenteric small arteries was assessed by pressurized myograph. MMI-treated animals displayed a decrease in serum thyroid hormones, an increment of plasma TSH and inflammatory cytokines, and a blunted vascular relaxation to acetylcholine, as compared with controls. Endothelial dysfunction resulted from a reduced nitric oxide (NO) availability caused by oxidative excess. Vascular-inducible NO synthase (iNOS) expression was up-regulated. S-methylisothiourea (an iNOS inhibitor) normalized endothelium-dependent relaxations and restored NO availability in arteries from 8-wk MMI-animals and partly ameliorated these alterations in 16-wk MMI rats. Similar results were obtained when MMI-induced hypothyroidism was prevented by T(4) replacement. Among controls, an impaired NO availability, secondary to oxidative excess, occurred at 16 wk, and it was less pronounced than in age-matched MMI animals. Both endothelial dysfunction and oxidant excess secondary to aging were prevented by apocynin (nicotinamide adenine dinucleotide phosphate oxidase inhibitor). Mesenteric superoxide production was reduced by S-methylisothiourea and T(4) replacement in MMI animals and abolished by apocynin in controls (dihydroethidium staining). MMI-induced mild hypothyroidism is associated with endothelial dysfunction caused by a reduced NO availability, secondary to oxidative excess. It is suggested that in this animal model, characterized by TSH elevation and low-grade inflammation, an increased expression and function of iNOS, resulting in superoxide generation, accounts for an impaired NO availability.