Thyroxine production would be halted at point C in the figure, leading to hypothyroidism and an enlarged goiter due to the lack of iodine for thyroid hormone synthesis.
In the context of iodine deficiency and its impact on thyroxine production, point C in the figure represents a critical stage where the synthesis of thyroid hormones is disrupted. Iodine is an essential component of thyroid hormones, including thyroxine (T4) and triiodothyronine (T3). Without sufficient iodine, the thyroid gland cannot produce these hormones effectively.
At point C, the absence of iodine hinders the thyroid's ability to incorporate it into the structure of thyroid hormones. As a consequence, the synthesis of thyroxine is halted. The body's negative feedback mechanisms respond to the low levels of thyroid hormones by increasing the release of thyroid-stimulating hormone (TSH) from the pituitary gland, attempting to stimulate the thyroid to produce more hormones.
However, in the absence of iodine, the thyroid remains unable to meet the demand for thyroid hormone production. Persistent stimulation by TSH, coupled with the inability to synthesize adequate thyroid hormones, leads to a condition known as hypothyroidism. One prominent manifestation of hypothyroidism is the development of a goiter, an enlarged thyroid gland.