Effect of not taking medicine after thyroid removal?

It is extremely important to take supplementary thyroid medicines when your thyroid is removed. Thyroid hormones regulate multiple metabolic processes and play an essential role in normal growth and development, and normal maturation of the central nervous system and bone. The metabolic actions of thyroid hormones include augmentation of cellular respiration and thermogenesis, as well as metabolism of proteins, carbohydrates and lipids. The protein anabolic effects of thyroid hormones are essential to normal growth and development.
If you don't have any thyroid hormone all these processes cannot be completed, and you'll experience symptoms of hypothyroidism.

Symptoms of Low Thyroid Levels:

Abnormal menstrual periods, Cold intolerance, Constipation, Depression, Fatigue, Joint or muscle pain, Paleness, Thin and brittle hair, Thin, brittle fingernails, Weakness, Weight gain (unintentional), Decreased taste and smell, Dry flaky skin, Hoarseness, Puffy face, hands, and feet, Slow speech, Thickening of the skin, Thinning of eyebrows.

Other symptoms that can occur with this condition:

* Absent menstruation
* Ankle, feet, and leg swelling
* Appetite loss
* Delayed growth of or missing teeth
* Drowsiness
* Dry hair
* Hair loss
* Joint stiffness
* Overall swelling
* Muscle pain
* Muscle spasms (cramps)
* Short stature
* Uncoordinated movement

Levothyroxine is a thyroid hormone. It works by replacing thyroid hormone when your body does not make enough on its own (or make any when your thyroid is removed).

For more information see the links below:
https://www.drugs.com/levothyroxine.html
https://www.drugs.com/pro/levothyroxine.html
https://www.drugs.com/health-guide/hypothyroidism.html