Hypothyroidism Has an Adverse Effect on Human Spermatogenesis: A Prospective, Controlled Study

Background: Abnormalities of spermatogenesis are associated with numerous diseases and aging. The objective of this study was to investigate the impact of hypothyroidism on human spermatogenesis and different sperm function tests. Methods: Twenty-five hypothyroid men and 15 normal individuals were investigated. Semen analysis, fructose and acid phosphatase measurements, teratozoospermia index (TZI), and acridine orange test were determined before and 6-9 months after the initiation of treatment with levothyroxine. Results: Morphology is the only sperm parameter that differs significantly between hypothyroid patients and controls (p < 0.0001). After treatment, morphology improved significantly (p < 0.001). Motility was also decreased before treatment in comparison with controls, and improved after treatment. However, the difference was not significant. TZI correlated with free thyroxine. Conclusions: Hypothyroidism has an adverse effect on human spermatogenesis. Morphology is the only sperm parameter that is significantly affected. Motility may also be affected, but further studies regarding this are needed. Screening for thyroid dysfunction in males who present with a defect in spermatogenesis is strongly recommended, and if hypothyroidism is noted, the response to thyroid hormone should be evaluated before initiating other treatments.