These are due to the hypocalcaemia that results from the decreased parathyroid function.
1. Paraesthesia - this is a sensation of numbness and tingling, like pins and needles, usually felt in the fingers, toes and around the mouth, and is due to impaired activity of sensory nerves.
2. Cramps - altered calcium levels cause abnormalities of muscle contraction resulting in cramps around the body. In particular it can cause laryngospasm (spasm of the muscles of the larynx).
3. Tetany - this is prolonged sustained involuntary contraction of muscles due to muscle nerve conduction problems. This can result in carpopedal spasm.
Carpopedal spasm - click to enlarge
4. Agitation and seizures - abnormal levels of brain activity can cause seizures and agitation