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The thyroid gland is one of the largest endocrine glands in the human body. The thyroid gland is a highly vascular, brownish-red gland located in the visceral compartment of the anterior region of the neck, spanning the regions between the C5 and T1 vertebrae and encircling the anterolateral trachea . The left and right lobes of the thyroid gland are connected by a central isthmus. Important processes in metabolism, growth, cardiac function, and calcium homeostasis are regulated by the thyroid hormones (thyroxine and triiodothyronine) and calcitonin.

Last updated: December 3, 2024 832 views

  • Thyroid gland characteristics: butterfly-shaped, endocrine gland composed of two lobes located inferior to the larynx and anterior to the trachea.
  • The isthmus connects the right and the left lobes of the thyroid.
  • The thyroid gland develops from the fusion of the median thyroid anlage with the two lateral thyroid anlages, which are derived from the pharyngeal pouches.

  • Production of thyroid hormones essential for regulating metabolism and growth
  • Parafollicular cells (C cells) produce calcitonin, which influences calcium homeostasis by lowering serum calcium (PTH antagonism).

  • The hypothalamus produces TRH ➜ TRH binds to membrane receptors in the pituitary glands and stimulates the formation and secretion of thyroidin stimulating hormone (TSH)
  • TSH is binds to receptors in the thyroid gland, which then receive additional iodine and synthesize triiodothyronine (T3) and thyroxine (T4).
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    • T3 and T4 inhibit the secretion of TRH as well as TSH
    • TSH also inhibits TRH secretion.