The true causes of many common illnesses often remain a mystery to medical researchers no matter how intense the investigation becomes. Internal shaking, muscle spasms, and extreme or chronic fatigue are no exception. While researchers continue their probing, much about the aetiology of these prevalent conditions remains unknown.
Hyperthyroidism refers to an overactive thyroid gland which is believed to cause the jitters and shaking, among other conditions.
Shaking or trembling are just two of the symptoms of anxiety and panic disorders, which can last up to 90 minutes.
Muscle spasms may result when muscles are overworked, especially by athletes and manual labourers.
Muscles that are not properly hydrated are also prone to developing muscle spasms because their cells contract.
Systemic illnesses and neurological disorders may both cause muscle spasms.
According to author John Zajaros, some suggest that stress may be a factor causing extreme fatigue or chronic fatigue syndrome. However, he points out, many prominent researchers have looked into the aetiology of chronic fatigue but "to no avail." But some researchers believe a genetic link may explain chronic fatigue since the condition has been diagnosed in members of the same family.