Case report described 18 months therapy strategy and management of unusual combination two rare diagnoses in the young cat. A 13-month-old neutered female domestic shorthair cat was presented with a 5-month history of repeated episodic weakness, dyspnoea, flaccidity, fainting, deteriorating over time to collapses with breathlessness and unconsciousness. Simultaneously polydipsia with polyuria and polyphagia with voluminous droppings and decreased interest in contact were observed. Hypersensitivity of carotid sinus and hyperthyroidism were documented. A permanent transjugular pacemaker was placed to prevent further life-threatening syncope, followed by subtotal thyroidectomy after 2 weeks. During 15 months until follow-up, there were neither recurrences of syncope nor signs of hyperthyroidism. Recently, the cat is completely without medication. Our observation indicates that hyperthyroidism can occur also in a young cat and that hypertensive carotic sinus can be successfully resolved by VVI pacemaker implantation.