A total of 12 studies were recruited for the current analysis for analyzing the impact of adding lithium to radioactive iodine for the management of hyperthyroidism. The cure rate of hyperthyroidism patients treated with lithium and iodine was considerably higher than that of those treated with iodine alone (p = 0.007). While splitting the total number of studies into subgroups, the variable result was reported as a substantial (p = 0.004) cure rate advantage for the lithium group in trials with 100 or more individuals. In randomized clinical trials, the difference between the two groups was not statistically significant (p = 0.10), however, the difference between the two groups in observational studies was statistically significant (p = 0.01; see also Observation Studies). Analysis of the influence of the intervention on thyroxine level, however, revealed no significant effect (P = 0.13).
LiCO3 has a 12-hour half-life, is completely absorbed after oral administration, is not metabolized, and is eliminated in its original form by the kidneys. All of the dose travels via the blood, the lymph, and the interstitial fluid before trickling slowly into the cells.[33] People who had a large thyroid gland, rapid iodine washout, and reduced iodine uptake had a lower cure rate status after RAI.[34] Lithium prolonged the half-life of RAI [35] and blocked the release of TH.[36] On the other hand, Thamcharoenvipas et al.[27] found that LiCO3 was detrimental for patients with Graves' illness who experienced a high rate of relapse. This may be owing to the fact that you took a very high dose of LiCO3 for three weeks—a total of 18,600 mg. Additionally, it was common practise at their hospital to use LiCO3 with 3.7 mBq/g of RAI for Graves' cases with quick turnover up take. The cumulative dose in the ten-day non-randomized experiment conducted by Oszukowska et al.[24] was 7500 mg. Additionally, the doses used in the randomized studies by Bal et al.[32] and Thamcharoenvipas et al.[27] were 18,600 mg for 21 days and 4,200 mg for seven days, respectively.
As for the secondary result, there was no significant statistical difference between the LiCO3 group and the control group, with three studies reporting lower serum T4. Patients treated with RAI alone increased their T4 levels and decreased their TSH levels for seven days, as shown by Sekulic et al.[23] Irradiation of the glands caused this reflex, whereas in the LiCO3 group, it disappeared. After four months, T4 and T3 levels suddenly dropped in the RAI group, as explained by Lingudu et al.[29] Especially in the case of geriatric and cardiac patients, this speedy regulation could prove beneficial.
The current meta-analysis found that patients treated with lithium prior to radioactive iodine had shorter remission times from hyperthyroidism and less severe elevations in thyroid hormones. This reduction in hormone levels was observed despite the fact that all patients in the study had been pretreated with antithyroid drugs, a common practice used to lessen the severity of hyperthyroidism following RAI. Whether or not this difference is clinically significant is debatable, but it may be relevant to the management of those most vulnerable to the morbidity associated with thyrotoxicosis, such as the elderly and those with cardiac comorbidities.
Further researches are needed to validate the safety and effectiveness of adjuvant lithium found in the majority of our trials, but if this is done, lithium may play a larger role in the treatment of hyperthyroidism. Failure rates for the treatment of Graves disease are as high as 10–15%, even when using high dose (10–15mCi) RAI therapy.[14, 37] Nearly 20% of cases with toxic multinodular goiter fail to respond to treatment.[38] Increasing RAI doses to decrease the failure rate has not improved the cure rate,[39, 40] and it has increased both the expense and the risk of complications. Although lithium improves the cure rate, this effect appears to be more pronounced at larger doses of RAI, suggesting that its use may translate to a lower failure rate in this scenario.
Lingudu et al.,[29] published findings for thyroid volumes 20 g and 20 g. Whereas Bal et al.[32] and Bogazzi et al.[22] published data based on thyroid volumes of 40 g and > 40 g, respectively. Therefore, only the RCTs [22, 32] comparing thyroid volume ( 40 g and > 40 g) could be included. Significant heterogeneity existed between the two RCTs. As the largest study, Bal et al. 2002,17 had a disproportionally large impact on the outcome of the meta-analysis. In addition, Bal et al.[32] employed a lower dose of RAI than the current recommendation (reference 3) and discontinued anti-thyroid medication for the shortest duration of all examined RCTs. These two variables may have contributed to the reduced cure rate in the included RCTs. Bogazzi et al.[22] did demonstrate a considerably higher cure rate with adjuvant Li compared to RAI. However, it was a considerably smaller study that lacked sufficient power. Only two randomized controlled trials [28, 32] examined the efficacy of adjuvant Li with RAI in the toxic nodular thyroid group. In these investigations, a limited number of patients had toxic nodular thyroid disease. Therefore, both studies had insufficient power to evaluate the outcome of toxic nodular thyroid disease. In addition, Bal et al.[32] contributed 51.9% to our research and demonstrated a 60% cure rate in the RAI plus adjuvant Li group (in toxic nodular thyroid group). Compared to Hammond et al.[28], the RAI with adjuvant Li group had an 80% cure rate. Lower cure rate reported by Bal et al.[32] may be explained by the methodology stated previously. Given the limited evidence, it is necessary to design randomized controlled trials to determine if adjunctive Li usage is useful for patients with toxic nodular thyroid disease and at various thyroid volumes.
Limitations
Because so many papers were omitted from the meta-analysis, numerous conclusions are possible. However, such papers were excluded from our meta-analysis since they did not meet the inclusion criteria. In addition, the influence of race, age, and gender on the presented results is not evaluated in all of the included studies. introducing bias into a study. The bias assessment of individual research found a lack of clarity regarding the risk of bias in a number of crucial categories, indicating that a significant degree of bias may exist within these studies. The risk of bias across research revealed an unbalanced publishing trend, indicating the possibility of bias in the body of literature. These findings collectively call for care in the interpretation of the data. Additional research is required to corroborate these results.