Indirect Basal Metabolism Estimation in Tailoring Recombinant Human TSH Administration in Patients Affected by Differentiated Thyroid Cancer: A Hypothesis-Generating Study

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.

Influence of Obesity Parameters on Different Regional Patterns of Lymph Node Metastasis in Papillary Thyroid Cancer

OBJECTIVE

Obesity increases risk of thyroid cancer. However, the association between obesity and the progression of papillary thyroid cancer (PTC) remains controversial. This retrospective study aimed to explore the relationship between obesity and regional patterns of lymph node metastasis (LNM) in PTC.

METHODS

We retrospectively reviewed data from 1015 patients with PTC. We calculated obese parameters, such as body mass index (BMI), body fat percentage (BFP), and body surface area (BSA). Logistic regression models were used to assess associations between obese parameters and the rate of lymph node metastasis (LNM), number of LNM, pattern of LNM, and lymph node ratio (LNR).

RESULTS

Higher BMI was not associated with different regional patterns of LNM in PTC. In men with PTC, high BFP was an independent predictor of total LNM, central lymph node metastasis (CLNM), total lateral lymph node metastasis (LLNM), multiple lateral lymph node metastasis, and simultaneous metastasis in lateral compartment. In addition, male patients with high BFP had higher central LNR and higher number of CLNM. For women, high BSA was an independent predictor of LLNM and level IV metastasis. Female patients with high BSA had higher number of CLNM.

CONCLUSION

BFP and BSA, possibly influenced by gender, were positively associated with the number and risk of LNM in different regions of PTC patients. However, BMI was not the predictor for aggressiveness of PTC in terms of LNM. Clinical decision-making for regional LNM in PTC patients should consider the factor of obesity.

Preoperative Thyroid Autoimmune Status and Changes in Thyroid Function and Body Weight After Bariatric Surgery

BACKGROUND

Bariatric surgery has emerged as the most effective therapy for morbid obesity. There is increasing evidence that bariatric surgery could alleviate systemic inflammation and influence thyroid function. The current study aimed to investigate the associations of preoperative thyroid autoimmune status with the changes in body weight and thyroid function after bariatric surgery.

METHODS

We recruited 101 patients with morbid obesity (44 men and 57 women) who received bariatric surgery at Zhongshan Hospital, Fudan University. Those who had used thyroid hormone replacement or antithyroid drugs were excluded. General linear models were used to compare the changes in body weight and thyroid function in participants with different thyroid autoimmune statuses.

RESULTS

After bariatric surgery, serum-free triiodothyronine (FT3) (4.94 ± 0.73 vs 4.33 ± 0.59 pmol/L, P < 0.001) and thyroid-stimulating hormone (TSH) (3.13 ± 1.59 vs 2.26 ± 1.26 μIU/mL, P < 0.001) were significantly reduced, accompanied by reductions in BMI (42.1 ± 7.6 vs 31.4 ± 6.5 kg/m², P < 0.001), and estimated basal metabolic rate (2002 ± 398 vs 1700 ± 336 kcal/day, P = 0.001) and an improvement in lipid profiles. Serum thyroperoxidase antibody (TPOAb) and thyroglobulin antibody (TgAb) levels also decreased significantly from 79.3 and 177.1 IU/mL to 57.8 and 66.0 IU/mL in participants with positive thyroid antibodies (P < 0.05). Further analysis showed that the positive preoperative thyroid autoimmune status was associated with less reduction in serum TSH (0.05 ± 1.59 vs - 1.00 ± 1.43 μIU/mL, P = 0.021) and BMI (- 8.3 ± 3.6 vs - 11.0 ± 4.5 kg, P = 0.049) after bariatric surgery.

CONCLUSION

Our study highlights a group of patients with morbid obesity, who have positive preoperative thyroid autoimmunity and less reduction in serum TSH levels and body weight after bariatric surgery.

Body surface area, height, and body fat percentage as more sensitive risk factors of cancer and cardiovascular disease

BACKGROUND

Limited studies have compared the association between various physical measurements and the risk of cancer or cardiovascular disease (CVD). We aim to explore the best-individualized indicators of cancer and CVD risk assessment.

METHODS

From May 2004 to December 2017, a community-based cohort in China involving 100 280 participants were enrolled. BMI, height, body surface area (BSA), and body fat percentage (BFP) were compared in parallel about cancer and CVD risk with the multivariable-adjusted Cox proportional hazard regression model.

RESULTS

Within the follow-up period, 3107 (3.10%) were diagnosed with cancer and 3721 (3.71%) had CVD. Per-level increased (in tertile: T1, T2, and T3 level) BSA, height, and BFP was positively associated with the risk of overall cancer [HR (95% CI): 1.10 (1.05-1.15), 1.12 (1.07-1.18), and 1.10 (1.03-1.16), respectively], whereas BMI was insignificant. Compared with the reference group (T2), the highest BSA level (T3) was positively associated with overall cancer incidence for both male [HR (95% CI): 1.28 (1.13-1.45)] and female [HR (95% CI): 1.13 (1.00-1.28)]. The BSA, height, and BFP also significantly associated with some site-specific cancers including thyroid, stomach, breast, urinary system, and skin cancer. Meanwhile, BFP presented a strong positive association with overall CVD [HR (95% CI): 1.22 (1.15-1.30) in trend] in both gender and associated with nearly all CVD subtypes especially the myocardial infarction and heart failure.

CONCLUSION

BSA, height, and BFP have more sensitivity in assessing cancer risk and BFP shows the largest hazard ratios for CVD incident. We provided valuable evidence for the application of height, BSA, and BFP in routine healthcare practice. These encouraging findings should be tested in more well-defined studies for risk prediction.