Hipotireoidismo primário simulando volumoso macroadenoma hipofisário

Abstract

A 21-year-old woman complaining of 8-month amenorrhea associated to weight gain, galactorrhea and frequent headaches, presented for clinical evaluation; her laboratory tests were: TSH: 1192 mUI/ml (0.27-4.2); TT4: 1.0 microg/dl (4.4-11.4 l); TT3: 0.41 ng/ml (0.7-2.1); prolactin: 69.2 ng/ml (3-20) and a diagnosis of myxedema associated to galactorrhea was made. A hypothalamic-pituitary magnetic resonance imaging (MRI) showed a suprasellar and intrasellar mass lesion of 1.9 x 1.4 x 1.9 cm, determining compression and deviation of the optic chiasm. Due to the possibility of hyperplasia of the TSH-producing cells, treatment of hypothyroidism was initiated with levothyroxine. Two months later, upon normalization of thyroid hormones and TSH levels, a second MRI showed an anatomically normal pituitary gland. Regression of the pituitary mass after treatment with levothyroxine confirmed the hypothesis of pituitary hyperplasia secondary to primary hypothyroidism. Our findings support the importance of determining thyroid function tests during the investigation of pituitary masses and thus avoiding an unnecessary surgery.

Pituitary hyperplasia resulting from primary hypothyroidism

“…In the literature, it has been suggested that in presence of markedly elevated TSH, absence of clinical features of hyperthyroidism, and low thyroid hormone values, one should suspect a diagnosis of pituitary enlargement secondary to primary hypothyroidism. [1,4] In this type of pituitary hyperplasia, the thyrotroph cells becoming enlarged by lack of negative feedback; indeed, the hormonal profile is usually straightforward, displaying unambiguous marked primary hypothyroidism with low circulating thyroid hormones and elevated TSH, easily reversible upon thyroid replacement. [5] Recognition of this entity is crucial (as in present case).…”

“…[1][2][3]5] This case also illustrates the importance of determining thyroid function tests during the investigation of pituitary masses and avoiding the need to perform pituitary surgery. [4]…”

Primary hypothyroidism masquerading pituitary macroadenoma

“…(11) Clinically the patients with pituitary hyperplasia can present with headache, visual symptoms and features of hypothyroidism. (1,3,7,14) It is important to understand that the headache may be due to hypothyroidism, although the exact underlying mechanism is not clear. (7) In many cases pituitary hyperplasias may be clinically silent and focal pituitary hyperplasia can be an incidental finding at autopsy.…”

Persistence of hyperprolactinemia after treatment of primary hypothyroidism and withdrawal of long term use of estrogen: are the tuberoinfundibular dopaminergic neurons permanently lesioned?

“…Several mechanisms are possibly involved in this occurrence: reduced secretion of some Prl inhibitory factors, increased secretion of TRH and enhanced pituitary sensitivity to tonic TRH secretion (1). Long lasting primary hypothyroidism can induce hyperplasia of TSH and Prl producing cells, causing a radiological image suggestive of a pituitary tumor (4)(5)(6)(7)(8).…”