What is a consequence of untreated or under-treated hypothyroidism?

The consequence of untreated or under-treated hypothyroidism can lead to the development of a goiter. A goiter is an enlargement of the thyroid gland that occurs as a compensatory mechanism when the thyroid is producing insufficient hormones. When the body senses low levels of thyroid hormones, it attempts to stimulate the thyroid gland to produce more by increasing the production of Thyroid Stimulating Hormone (TSH). The chronic stimulation by TSH can cause the gland to enlarge, resulting in a goiter.

Thyroid storm is not a result of untreated hypothyroidism; rather, it is a life-threatening condition often associated with hyperthyroidism. Cystitis, which is inflammation of the bladder, is unrelated to thyroid function, and hyperthyroidism is characterized by excessive hormone production, not a deficiency as seen in hypothyroidism. Therefore, among the given options, goiter is the most relevant consequence of untreated or under-treated hypothyroidism.