Significance of calcium: its correlation with red and white muscle contraction, fatigue and potential

According to the predominant types of muscle fibers in an individual, they will have the ability to perform different types of exercises (both aerobic and anaerobic). To comprehend the mechanism of muscle fibers, which can act in diverse ways, enhancing either resistance or power, it is essential to examine the significance of calcium. Calcium plays a crucial role in both red and white muscle fibers. The release of calcium in white (fast-twitch) muscle fibers is significantly greater and faster, resulting in increased energy consumption, facilitating explosive physical activities. Conversely, in red (slow-twitch) muscle fibers, the release of calcium occurs in smaller amounts and over a prolonged period, leading to sustained energy consumption. The characteristics of contraction in red fibers enable endurance activities. A reduction in the amount of calcium results in diminished muscle contractile capacity, known as fatigue. The primary contributing factor, as previously mentioned, is the decline in calcium, but factors such as lactic acid and the dephosphorylation of the myosin head also contribute to its onset.

Drug induced iatrogenic Cushing抯 syndrome

Drug-induced (iatrogenic) Cushing's syndrome results from excessive or prolonged exposure to glucocorticoids, commonly prescribed for autoimmune, inflammatory, and hematological disorders due to their anti-inflammatory, immunosuppressive, and proapoptotic effects. Despite their therapeutic benefits, these medications can lead to a range of multisystemic symptoms mirroring those of endogenous Cushing抯 syndrome. This review aims to elucidate the causes, clinical presentation, diagnosis, and management of iatrogenic Cushing's syndrome, emphasizing awareness of medications that can trigger its onset. The following review covers cortisol physiology, Cushing's syndrome etiology and subtypes, hypercortisolism complications and prognosis, and strategies for glucocorticoid withdrawal. This article synthesizes key findings and recommendations, highlighting challenges and controversies in the diagnosis and treatment of iatrogenic Cushing's syndrome.