The increased level of TSH may potentiate the risk of thyrotroph
hyperplasia and possible adenoma formation (29-32).
Invasion is characteristic of thyrotroph adenomas, silent corticotroph adenomas, and the unusual plurihormonal silent subtype 3 adenomas.
Pituitary thyrotroph hyperplasia mimicking prolactin-secreting adenoma.
Pituitary pseudotumor (pituitary thyrotroph
hyperplasia) caused by unrecognized and untreated hypothyroidism has been described as a rare condition, mostly in adults.
Thyroid stimulating hormone is a peptide hormone, composed of a distinct [beta]-subunit and a common [beta]-subunit that is secreted by the thyrotroph
cells of the anterior pituitary gland.
TSH below normal TSH above normal Primary hyperthyroidism Primary hypothyroidism Pituitary/hypothalamic disease Pituitary thyrotroph
adenoma with central hypothyroidism Pituitary resistance to thyroid hormone (central hyperthyroidism) Generalized thyroid hormone resistance Prolonged thyrotroph
cell Thyrotoxicosis from overly rapid suppression after recent correction of severe hypothyroidism hyperthyroidism in euthyroid with parenteral [T.
3], suggests altered pituitary thyrotroph
or hypothalamic responsiveness to circulating thyroid-hormone levels.
Both TRH and somatostatin are also detectable by radioimmunoassay in thyrotrophs
at embryonic day 14 (Harvey et al.
More resilient cells include corticotrophs and thyrotrophs
The anterior lobe consists of several different cell types (somatotrophs, mammotrophs, corticotrophs, thyrotrophs
, and gonadotrophs), which are involved in the biosynthesis and secretion of key hormones (growth hormone, prolactin, adenocorticotropic hormone, thyroid-stimulating hormone, and follicle-stimulating hormone/ luteinizing hormone, respectively) that regulate multiple, diverse, and important physiologic and metabolic functions in the human body (2).
Investigations revealed hyperprolactinemia and ACTH deficiency with normal function of the rest of the pituitary hormone-producing cells including thyrotrophs
In hypothalamic disease, there is a delayed and exaggerated response to TRH because the thyrotrophs
take some time to "wake up" after a prolonged lack of stimulation by endogenous TRH.