Correlation between sperm parameters and circulating thyroid hormones and testosterone concentrations in Labrador Retriever dog

Thyroid hormones physiologically regulate the semen quality, by altering testosterone concentrations, and different seminal parameters, as well as sperm motility, viability and semen volume. Serum thyroxine (T₄), free thyroxine (fT₄), thyroid-stimulating hormone (TSH) and testosterone (T) concentrations were measured in 26 adult Labrador Retriever dogs (n. 20 normospermic and n. 6 azoospermic groups), aged 3 ± 0.5 years old, to determine their specific references, by taking into account the related conventional and kinematic sperm parameters and clinical ultrasound evaluations. The mean values of T₄, fT₄, TSH and T concentrations, as soon as those of sperm parameters and clinical evaluations of normospermic group were in line with dog’s physiological range of literature data. Normospermic group showed significant correlations between T₄ and T (r = −0.681; p <.01), sperm progressive motility (%) (r = −0.623; p <.01), and sperm non-progressive motility (%) (r = 0.625; p <.02). The azoospermic group showed higher T₄, fT₄, TSH and lower T concentrations, compared to normospermic group, and a positive correlation between T₄ and T (r = 0.8548; p <.046). The use of breed-specific hormonal ranges and sperm parameters will improve the knowledge of their interaction in Labrador Retriever dogs, adding a new segment of scientific literature.