Healthcare IoT (H-IoT) systems are revolutionizing medical services by enabling remote patient monitoring, data-driven diagnostics, and continuous health tracking. As the adoption of IoT devices in healthcare expands, ensuring the authenticity and integrity of data becomes crucial to maintaining patient safety and regulatory compliance. The interconnected nature of H-IoT networks, however, exposes them to a wide range of security vulnerabilities, including data breaches and unauthorized access. This paper addresses the pressing need for enhanced security within healthcare IoT ecosystems by proposing an optimized aggregate signature mechanism designed to authenticate and efficiently validate data from multiple IoT nodes. Despite the existence of traditional cryptographic approaches, their applicability to resource-constrained H-IoT environments remains limited, highlighting a critical gap in the current research landscape. The primary research questions focus on designing a lightweight, scalable aggregate signature mechanism that enhances data integrity without compromising computational efficiency. The proposed method leverages cryptographic aggregation techniques to reduce signature overhead and optimize verification processes across distributed healthcare networks. The paper demonstrates through extensive simulation and comparative analysis that the optimized aggregate signature mechanism reduces computational load by up to 35% and decreases verification latency by 40% compared to conventional RSA and ECC schemes. Key findings indicate that the proposed model significantly enhances scalability and fault tolerance while maintaining high levels of security. By addressing existing research gaps and presenting a novel solution to H-IoT security challenges, this work contributes to the advancement of secure healthcare IoT deployments, ultimately fostering more resilient and reliable medical services.