FUNCTIONAL PITUITARY TUMOR IN AN ADULT POSSIBLY SECONDARY TO LONG-STANDING MYXEDEMA

Combined thyrotroph and lactotroph cell hyperplasia simulating prolactin-secreting pituitary adenoma in long-standing primary hypothyroidism

Primary hypothyroidism accompanies more than 50% of clinically significant pituitary thyrotroph adenomas. Hypothyroidism may also produce pituitary enlargement secondary to thyrotroph hyperplasia and present with a sellar mass and hyperprolactinemia. Three hypothyroid patients who presented with presumed prolactin-producing adenomas are reported. Although laboratory and radiologic abnormalities of pituitary enlargement may resolve after corrective thyroid therapy, our patients showed no such response and underwent operation. Histologic examination revealed no adenomas, but thyrotroph and lactotroph hyperplasia were present. Thyrotroph hyperplasia probably results from lack of negative feedback of thyroid hormone upon the anterior pituitary. Whether this is due to hypothalamic release of thyrotropin-releasing hormone (TRH) or another mechanism is unclear. Lactotroph hyperplasia may result from excess TRH, which stimulates lactotrophs with resultant hyperprolactinemia, or from reduced hypothalamic dopamine, thereby facilitating prolactin secretion. This study suggest that (a) hyperprolactinemia in hypothyroidism is not necessarily due to the "stalk section effect" secondary to pituitary enlargement, and (b) patients with primary hypothyroidism and sellar mass should initially be managed medically so that potentially reversible pituitary hyperplasia is not mistaken for adenoma.

Pituitary thyrotroph hyperplasia mimicking prolactin-secreting adenoma

A 32-year-old woman with persistent postpartum galactorrhea, hyperprolactinemia and a sellar configuration compatible with pituitary adenoma underwent transsphenoidal surgery. Mild hyperthyroidism had been suspected clinically preoperatively and thyroxine plus cortisol therapy was given. Morphological features of pituitary thyrotroph hyperplasia were present as shown by light microscopy, immunoperoxidase staining and electron microscopy. The thyrotroph hyperplasia was secondary to primary hypothyroidism as demonstrated by the TSH response to TRH stimulation and subsequent suppression with thyroid hormone treatment. Although prolonged severe hypothyroidism has been reported to cause pituitary enlargement, this is the first case of thyrotroph hyperplasia with detailed morphologic study of the surgically-removed adenohypophysial tissue. The presentation of this patient calls attention to the possibility of mistaking pituitary enlargement due to primary hypothyroidism for a prolactinoma.

Pituitary thyrotropic adenoma associated with congenital hypothyroidism. Report of two cases

Two patients with congenital hypothyroidism and thyroid-stimulating hormone-secreting pituitary adenomas are described. Both patients had a history of long-standing, inadequately treated hypothyroidism accompanied by markedly elevated levels of serum thyroid-stimulating hormone. Pituitary tissue, obtained at autopsy in the first patient and at surgery in the second, disclosed a thyrotropic adenoma. Immunocytochemical studies with anti-thyroid-stimulating hormone antisera showed both tumors to be strongly immunoreactive. Such thyrotropic adenomas of the pituitary gland are presumed to occur as the result of protracted pituitary stimulation secondary to long-standing thyroid deficiency.

Gonadotroph cell adenoma of the pituitary in a women with long-standing hypogonadism

A 57-year-old woman, with long-standing hypogonadism secondary to irradiation of the ovaries, was found to have a pituitary tumor which was removed and investigated by histology, immunocytology and electron microscopy. Histologically, the tumor corresponded to a chromophobe, slightly PAS positive adenoma and the immunoperoxidase stain revealed the presence of both FSH and LH in the cytoplasm of the adenoma cells. The structural features of the adenoma cells resembled those of FSH cells in the nontumorous adenohypophysis. We thus believe that pituitary adenomas consisting of gonadotrophin-producing cells occur and that these may produce both FSH and LH. The relation between the gonadotrophin-producing adenoma and the preceding hypogonadism is uncertain.

Clinical, biochemical, and radiologic reversibility of hyperprolactinemic galactorrhea-amenorrhea and abnormal sella by thyroxine in a patient with primary hypothyroidism

A case of primary hypothyroidism associated with postpartum galactorrhea-amenorrhea is reported. The configuration of the sella was compatible with pituitary adenoma, but prolactin dynamics did not support an autonomous secretory state. Replacement therapy with thyroxine led to complete reversal of clinical, radiologic, and biochemical abnormalities.

Primary hypothyroidism and galactorrhea

Ten of 16 women with primary hypothyroidism and high thyrotropin (TSH) concentrations had high serum prolactin (PRL) concentrations. A positive correlation was observed between the basal TSH and PRL levels in the hypothyroid patients. Five of these patients complained of persistent galactorrhea after delivery. After treatment with triiodothyronine (T3), the elevated TSH and PRL levels fell to within normal ranges, and the galactorrhea disappeared. It is suggested that the elevated serum PRL levels of patients with primary hypothyroidism are mediated by feedback-induced thyrotropin-releasing hormone (TRH) secretion or an enhanced response to endogenous TRH, and that the combination of delivery and the PRL excess may induce persistent galactorrhea in patients with primary hypothyroidism.

Primary thyroid failure presenting as a pituitary tumour

A 20-year-old female was referred as a pituitary tumour with failure to grow. Primary hypothyroidism from the age of 8 had been diagnosed at the age of 11, when the patient was put on thyroid replacement therapy. Routine investigations showed normal anterior pituitary function, and confirmed the diagnosis of primary hypothyroidism. A needle biopsy of the pituitary gland revealed an empty fossa. The possible relation of the empty sella with the primary hypothyroidism is discussed. A chromosome anomaly, deletion of the short arm of an X chromosome, was found and its contribution to the delayed growth is discussed.

Galactorrhea in males with tumors in the region of the pituitary gland

✓ The pathophysiology of galactorrhea in males with pituitary tumors is discussed, two cases are presented, and previously-reported cases are reviewed. Hypersecretion of prolactin is probably the basis for the galactorrhea. Prolactin may be secreted by the tumor itself, or the remaining normal pituitary tissue may oversecrete if the hypothalamus or the pituitary stalk is compressed.