1.Cretinism: it is caused due to undersecretion during growth years. It two main effects are:
- Dwarfism: due to failure of the skeleton to grow and mature.
- Mental retardation: due to failure of the brain to develop fully Cretins also show retarded sexual development, yellowish skin colour, round face, large thick producing tongue and thick nose, Metabolism is lowered by 30 to 40 % resulting in low body temperature, and slow heart rate.
2.Myxedema: caused due to undersecretion in adults, this disorder is characterized by edema (retention of fluids) that causes the facial muscles to swell and look puffy. Other effects include slow heart rate, low body temperature, sensitivity to cold, general lethargy and a tendency to gain weight. It is more frequent in females.
3.Simple goitre: It is generally caused due to deficiency of iodine in the diet. It may also develop if the intake of iodine is not increased during conditions that put a high demand on the body for thyroxine (e.g. pregnancy, exposure to cold, high fat and protein diet). It manifests as a disproportionate swelling of the neck.
- The thyroid is enlarged by possibly 2-3 times its original size. Fluid is retained behind the eye which causes the eye to produce
- The metabolic rate becomes abnormally high with effects such as increased pulse, high blood pressure, high body temperature, flushed skin, tremor, sweating and heat intolerance. Appetite increases but the person loses weight. More frequent in females.