Posthemithyroidectomy Hypothyroidism: Updated Meta-Analysis of Risk Factors and Rates of Remission

INTRODUCTION

The aim of this study was to determine the incidence and risk factors for hypothyroidism, both clinical and subclinical, following hemithyroidectomy in preoperatively euthyroid patients, as well as hypothyroidism remission and its time of remission.

MATERIALS AND METHODS

A search was performed in Medline (via PubMed), Web of Science, and the Cochrane Library using the keywords "hemithyroidectomy + postoperative + hypothyroidism" and "hemithyroidectomy + hormone supplementation".

RESULTS

Fifty-four studies with a total of 9,999 patients were included. After a mean follow-up interval of 48.2 mo, the pooled hypothyroidism rate was 29%. The subclinical hypothyroidism rate was 79% of patients with hypothyroidism (18 studies). Moreover, a meta-analysis of 12 studies indicated a pooled hypothyroidism remission rate after hemithyroidectomy of 42% (95% CI: 24%-60%). Older patient age (MD = -2.54, 95% CI = -3.99, -1.10, P = 0.0006), female gender (OR = 0.69, 95% CI = 0.58, 0.82, P < 0.0001), higher preoperative thyroid-stimulating hormone levels (MD = -0,81, 95% CI = -0.96, -0.66, P < 0.00001), pathological preoperative anti-thyroid peroxidase antibodies (OR = 0.37, 95% CI = 0.24, 0.57, P < 0.00001) and anti-thyroglobulin antibodies (OR = 0.52, 95% CI = 0.36, 0.75, P = 00,005), and right-sided hemithyroidectomy (OR = 0.54, 95% CI = 0.43, 0.68, P < 0.00001) were associated with postoperative hypothyroidism development. In metaregression analysis, Asia presented a significantly higher hypothyroidism rate after hemithyroidectomy (34.6%, 95% CI = 29.3%-9.9%), compared to Europe (22.9%, 95% CI = 16.2%-29.5%, P = 0.037) and Canada (1.8%, 95% CI = -22.6%-26.2%, P = 0.013).

CONCLUSIONS

Hypothyroidism is a frequent and significant postoperative sequela of hemithyroidectomy, necessitating individualization of treatment strategy based on the underlying disease as well as the estimated risk of hypothyroidism and its risk factors.

DESIGN AND FABRICATION OF A PEDIATRIC THYROID PHANTOM FOR USE IN RADIO-IODINE UPTAKE MEASUREMENT, IMAGE QUALITY CONTROL AND DOSIMETRY

Estimating internal contamination from 131I for children in nuclear accidents is a crucial subject in the radiation protection field. Throughout this paper, an urgent and simple method was proposed for measuring 131I inside the pediatric thyroid gland by constructing a neck and thyroid phantom. For this purpose, CT scan images of healthy child's thyroids were obtained, and the sizes of different parts were determined by a 3D slicer image processing software. Girls with the body surface area between 0.95 and 1.05 were involved in this study. The fabricated phantom is composed of 5 cylindrical slabs of 2-cm thickness, and several small holes were constructed for TLD dosemeters near the thyroid gland and all other parts of the neck. The phantom was constructed utilizing a 3D printer with acrylonitrile butadiene styrene plastic. The thyroid phantom was filled with radioiodine-131, and calibration curves were plotted for contamination estimation. A nodular thyroid phantom was also constructed. The nodular phantom or the resolution phantom has 4 removable parts containing cylindrical holes with diameters of 3, 6, 9 and 12 mm. These holes on the thyroid glands can be filled with different activities of radionuclides to serve as hot and cold spots for quality control of nuclear medicine images. The results show that the designed phantom is applicable in different fields such as nuclear image quality and resolution tests, dosimetry and iodine thyroid uptake estimation in nuclear medicine departments, and nuclear emergency monitoring.

Prevalence of and risk factors for hypothyroidism after hemithyroidectomy: a systematic review and meta-analysis

PURPOSE

This systematic review and meta-analysis evaluated the prevalence of and risk factors for hypothyroidism following hemithyroidectomy as new evidence obtained in recent years warranted an update of previous meta-analyses.

METHODS

The PubMed, Embase, and Cochrane Library databases were searched through November 1, 2019, for articles examining the hypothyroidism prevalence and risk factors after lobectomy. The prevalence rate, risk ratio (RR), weighted mean difference (WMD) and standardized mean difference (SMD) were assessed by conducting a meta-analysis of proportions, binary variables, and continuous variables, respectively, using random-effects models.

RESULTS

Fifty-one studies showed a pooled risk of 29.9% (95% confidence interval (CI), 24.6-35.2%) for hypothyroidism following hemithyroidectomy. Risk factors for the development of postoperative hypothyroidism included the female sex (RR, 1.169; 95% CI, 1.040-1.314; P = 0.009), a higher preoperative thyrotropin (TSH) level (RR, 2.955; 95% CI, 2.399-3.640; P = 0.000), a lower preoperative FT4 level (SMD, -0.818; 95% CI, -1.623--0.013; P = 0.047), concomitant lymphocyte infiltration (RR, 1.558; 95% CI, 1.203-2.018; P = 0.001), Hashimoto's thyroiditis (HT) (RR, 1.480; 95% CI, 1.192-1.838; P = 0.000), a lighter weight of the remaining gland (WMD, -2.740; 95% CI, -3.708--1.772; P = 0.000), and a right side lobectomy (RR, 1.404; 95% CI, 1.075-1.835; P = 0.013).

CONCLUSIONS

Hypothyroidism is a significant complication after lobectomy, and appropriate and personalized surgical strategies should be designed after a careful preoperative assessment based on the estimated risk of hypothyroidism and risk factors.

Retrospective Study of Tc-99m Thyroid Scan in Patients with Graves' Disease: Is There Significant Difference in Lobar Activity?

PURPOSE

Graves' disease (GD) is the most common cause of hyperthyroidism. It was reported that the right thyroid lobe is generally larger, and it is more likely to be affected by thyroid disorders. The aim of the current study is to verify preferential affection of one of the thyroid lobes and incidence of higher activity of either thyroid lobe in patients with GD through analysis of quantitative data of Tc-99m thyroid scan and possible relation of different thyroid lobar activity to gender, age, and total thyroid uptake (TTU) level.

MATERIALS AND METHODS

Retrospective analysis of quantitative data of Tc-99m thyroid scan in patients with GD was done. Total and lobar thyroid uptake levels were analyzed and correlated with age, gender, and TTU.

RESULTS

GD was reported in 222 patients, representing 76.6% of those with hyperthyroidism, women represent 70.3% of patients. The right thyroid lobe uptake (RLU) figures were significantly higher compared to the left in the whole group as well as in women and in young patients (<40 years). This significance was lost in men and in old patients. Equal lobar uptake was found in 11 patients. 138 patients (62.2%) had higher RLU, while the remaining 73 patients (32.8%) had higher left thyroid lobe uptake, with statistically significant difference. This significant difference was found in women and in young patients and was absent in men and old patients. There is an increase in the incidence of patients with higher RLU in association with an increase in TTU. All women with TTU >30% had higher RLU figures.

CONCLUSION

There is significant preferential thyroid lobar affection in favor of the right thyroid lobe in patients with GD, with significantly higher RLU figures and significantly more incidence of patients with higher right lobar activity. This significance is maintained in women and in young patients and lost in men and old patients. The incidence of higher right thyroid lobe activity also increases in association with increase in TTU. Our results emphasize the value of Tc99m thyroid scan in patients with GD, especially when surgery is the treatment of choice, helping to tailor suitable surgical procedure for each individual patient.

The Recovery of Thyroid Function in Low-Risk Papillary Thyroid Cancer After Lobectomy: A 3-Year Follow-Up Study

PURPOSE

Management strategies after lobectomy for low-risk papillary thyroid carcinoma (PTC) are controversial. This study aimed to identify the proportion of patients among low-risk PTC patients who do not require hormone replacement therapy and to evaluate the risk factors for postoperative hypothyroidism after lobectomy.

PATIENTS AND METHODS

The records of 190 PTC patients who underwent thyroid lobectomy from January 2017 to December 2018 were retrospectively reviewed. Clinicopathological characteristics and follow-up data were collected. Univariate and multivariate analyses were performed to identify the risk factors associated with postoperative hypothyroidism and the recovery of thyroid function.

RESULTS

In summary, 74.21% of patients (141/190) had normal thyroid function without levothyroxine supplementation, while 40.53% (77/190) developed temporary or permanent hypothyroidism. Multivariate analysis indicated that higher preoperative thyroid-stimulating hormone (TSH) levels (>2.62 mIU/L), Hashimoto's thyroiditis (HT), and right lobectomy were associated with hypothyroidism (all P<0.05). The Area Under Curve (AUC) by logistic analysis was 0.829. Twenty-eight (28/77, 36.4%) patients recovered to the euthyroid state in the first year after surgery, and this recovery was significantly associated with preoperative TSH level. Forty-nine (49/77, 63.6%) patients developed persistent hypothyroidism. The thyroid function of most patients (11/28, 39.3%) recovered in the third month after surgery.

CONCLUSION

Patients with a lower level of preoperative TSH, with left lobectomy and without Hashimoto's thyroiditis had a higher chance of normal thyroid function within the first year after lobectomy. The recovery of thyroid function was associated with the level of preoperative TSH.

Clinical Features of Early and Late Postoperative Hypothyroidism After Lobectomy

CONTEXT

Lobectomy is preferred in thyroid cancer to decrease surgical complications and avoid lifelong thyroid-hormone replacement. However, postoperative hypothyroidism, requiring thyroid-hormone replacement, may occur.

OBJECTIVE

We aimed to identify the incidence and risk factors of postoperative hypothyroidism to develop a surveillance strategy after lobectomy for papillary thyroid microcarcinoma (PTMC).

METHODS

This historical cohort study involved 335 patients with PTMC treated by lobectomy. Postoperative thyroid functions were measured regularly, and patients were prescribed levothyroxine according to specific criteria. Patients not satisfying hormone-replacement criteria were closely followed up.

RESULTS

Postoperative hypothyroidism occurred in 215 patients (64.2%) including 5 (1.5%) with overt hypothyroidism and 210 (62.7%) with subclinical hypothyroidism. Forty patients (11.9%) were required thyroid hormone replacement. One hundred nineteen patients (33.5%) experienced temporary hypothyroidism and spontaneously recovered to euthyroid state. High preoperative thyroid-stimulating hormone (TSH) was the most important factor predicting postoperative hypothyroidism and failure of recover from hypothyroidism (odds ratio [OR], 2.82 and 1.77; 95% confidence interval [CI], 2.07 to 3.95 and 1.22 to 2.63; P < 0.001 and 0.002, respectively). Of the 215 patients eventually developing postoperative hypothyroidism, 70 (32.6%) developed hypothyroidism after the first postoperative year. Postoperative 1-year TSH levels were able to differentiate patients developing late hypothyroidism or euthyroidism (OR, 2.29; 95% CI, 1.68 to 3.26; P < 0.001).

CONCLUSIONS

Preoperative and postoperative TSH levels might be predictive for patients who develop postlobectomy hypothyroidism and identify those requiring long-term surveillance for hypothyroidism. Additionally, mild postoperative hypothyroidism cases should be followed up without immediate levothyroxine replacement with the expectation of spontaneous recovery.

Genetic and environmental influence on thyroid gland volume and thickness of thyroid isthmus: a twin study

OBJECTIVES

Decreased thyroid volume has been related to increased prevalence of thyroid cancer.

SUBJECTS AND METHODS

One hundred and fourteen Hungarian adult twin pairs (69 monozygotic, 45 dizygotic) with or without known thyroid disorders underwent thyroid ultrasound. Thickness of the thyroid isthmus was measured at the thickest portion of the gland in the midline using electronic calipers at the time of scanning. Volume of the thyroid lobe was computed according to the following formula: thyroid height*width*depth*correction factor (0.63).

RESULTS

Age-, sex-, body mass index- and smoking-adjusted heritability of the thickness of thyroid isthmus was 50% (95% confidence interval [CI], 35 to 66%). Neither left nor right thyroid volume showed additive genetic effects, but shared environments were 68% (95% CI, 48 to 80%) and 79% (95% CI, 72 to 87%), respectively. Magnitudes of monozygotic and dizygotic co-twin correlations were not substantially impacted by the correction of covariates of body mass index and smoking. Unshared environmental effects showed a moderate influence on dependent parameters (24-50%).

CONCLUSIONS

Our analysis support that familial factors are important for thyroid measures in a general twin population. A larger sample size is needed to show whether this is because of common environmental (e.g. intrauterine effects, regional nutrition habits, iodine supply) or genetic effects.

The thyroid lobes: the different twins

Although differences in size of the right and left thyroid lobes are well defined, differences in morphology, follicles structure, cAMP production, thyrotropin receptor, and protein involved in cell signalling have not previously been reported. This study provides morpho-functional data of right and left thyroid lobes by biochemical, immunohistochemistry, immunoblotting and immunofluorescence analysis. We demonstrate that, in comparison with the left lobe, the right lobe has a higher activation index, is more sensitive to thyrotropin treatment, is rich in thyrotropin receptor and caveolin 1 involved in thyroid hormone synthesis as well as in epithelial thyroid cell homeostasis, is characterised by a high content of molecules involved in cell signalling such as stat3, raf1, sphingomyelinase and sphingomyelin-synthase whose activity ratio is necessary for epithelial cell activity and finally has more areas calcitonin-dependent. The relation between structure/function of right lobe and its susceptibility to the higher risk of pathological modifications with respect the left lobe is discussed.