To investigate the effect of thyroid hormone levothyroxine (L-T₄ ) on pregnancy outcomes and expression of caveolin-1 in rat models of thyroid dysfunction. Materials and Methods: One hundred Wistar rats (SPE grade, 60 female and 40 male) were randomly divided into three groups of control, model (hypothyroidism), and treatment (hypothyroidism + therapy with L-T₄ ) groups. Pregnant rats were investigated for pregnancy outcomes (litter size, number of dead fetus, placental index, body weight and length, and tail length of neonatal rat). Expression of caveolin-1 in placenta was analyzed using qRT- PCR and Western blot. Results: The modeling success rate was 75%. Investigations showed that the litter size, number of dead fetus, placental index, body and length, and tail length of neonatal rat in the models were significantly lower than those in control rats (p < 0.05), and significantly different from those in the treatment group (p < 0.05) except for the tail length (p > 0.05). The expression level of caveolin-1 in placenta was significantly higher in models than that in control (p < 0.05). Conclusion: Propylthiouracil (PTU) can successfully induce hypothyroidism in rat and hypothyroidism can seriously hinder the pregnancy process, resulting in developmental disorders in fetal rat.