Methods
Protocol and registration: The study protocol was established and recorded in the International Prospective Register of Systematic Reviews (Prospero: CRD42020198387).
Eligibility criteria: Studies investigating the proportion of human subjects with accompanying thyroid disorders among PE or DE sufferers or vice versa, correlation studies evaluating serum TSH with IELT and/or PRO measures of the EjD sufferers and measuring treatment effects that aim to establish a euthyroid state on the IELT and/or PRO measures of thyroid dysfunction sufferers were considered for this review. Both studies performed in the population and hospital settings were eligible in the case of appropriate ethical review board approval.
Information sources and search: An electronic data search was performed on Medline (via PubMed) without any time limit. A query by the different combinations of the following keywords: “ejaculation” and “thyroid,” “serum TSH,” “serum T3,” and “serum T4”was performed on July 3rd 2020 and updated on November 3rd 2020.
Study selection: Initial screening via review keywords on PubMed was performed by the first author and title and abstract of the journal articles were evaluated for eligibility. Randomized and non-randomized studies on human subjects that declare ethical approval and clearly report all of the components of the population, interventions, comparators, and outcome measures of the trial were eligible for our review. Reviews and meta-analyses of existing data were not included in the current study. Irrelevant reports were removed, and candidate studies for the scope of the current review were finally evaluated for eligibility with their full-text files. Finally, the relevance of the studies was assessed with both review authors not blinded to the names and institutions of the study authors. The study flow diagram is shown in Figure 1 and characteristics of the included studies are shown in Table 1.
Risk of bias in individual studies: We established the risk of bias assessment tool for eligible studies specific to the current review and classified all of the included studies according to their grade and type of bias according to GRADE recommendations for evaluation of certainty of the evidence (Table 2) (Guyatt et al., 2008).
Summary measures: We rendered the presence of EjD, either PE or DE, as a dichotomous qualitative outcome measure. The mean PRO measures of the subjects and the mean of the IELT measurements in the reviewed studies were quantitative outcome measures.