Pituitary gland adenoma

The EPA Office of Pesticide Programs reviewed the data for the tumorigenicity of triphenyltin hydroxide and classified it as a possible human carcinogen (Group B2) based on the tumors found in both rats and mice during chronic studies of carcinogenicity. The most appropriate estimate of the unit risk in human equivalents was a q1 of 2.8 (mg/kg/day) from the data on pituitary gland adenomas in female rats. 

The relationship between Toxoplasma gondii infection and neoplasia, including ocular tumours, gliomas, meningiomas, pituitary gland adenomas, leukemia and lymphomas has been reported (Khurana et al. 2005). In these studies is not clear if Toxoplasma has a role in tumorigenesis or if it is an opportunistic agent whose development is enhanced by host immunosuppression. 

Figure 3.58 (a) Side view of a pituitary gland adenoma, (b) Top view (slice) of the adenoma. (Images courtesy of H.T. Alberry, D. Derico, and M. Farrell, Albany Advanced Imaging, Albany, NY.)... 

ACTH-dependent Cushing s syndrome is usually caused by overproduction of ACTH by the pituitary gland, causing adrenal hyperplasia (Cushing s disease). Pituitary adenomas account for about 80% of these cases. Ectopic ACTH-secreting tumors and nonneoplastic corticotropin hypersecretion are responsible for the remaining 20% of cases. 

Methyl bromide was tested by oral administration in rats and by inhalation in mice and rats. In one 90-day study by oral administration in rats, methyl bromide was reported to produce squamous-cell carcinomas of the forestomach. In a second, 25-week study designed to investigate further the findings of the previous study, early hyperplastic lesions of the forestomach developed after 25 weeks of continuous treatment by gavage. In two inhalation studies in mice, no significant increase in the incidence of tumours was observ ed. In one inhalation study in rats, an increase in the incidence of adenomas of the pituitary gland was observed in high-dose male rats. In another study in rats, no increase in tumour incidence was observed. 

Triphenyltin hydroxide caused dose-related cystoid changes in the pars intermedia of the pituitary gland for male and female mice administered this compound for 52 or 104 weeks at doses of 0.3-6.2 mg/kg/day (Tennekes et al. 1989a). Up to 40% of the males and 80% of the females were affected at 52 weeks by the highest dose. At the end of 104 weeks, 72.3% of the high dose males and 55.6% of the females exhibited the cystoid changes. The lower incidence in females at 104 weeks related to a high early mortality from fatal pituitary adenomas (see Section 2.2.2.8). 

Cushing s syndrome (hypercorticism) is an endocrine hormone disorder caused by high levels of cortisol in the blood. Cushing s disease refers to one specific cause, a non-cancerous tumour (adenoma) in the pituitary gland that produces a large amount of ACTH, which in turn elevates cortisol. It can usually be cured by surgery. 

ECD is nearly always associated with hypertrophy, adenomatous h3q>erplasia or, in the most advanced cases, a functional adenoma of the pars intermedia of the pituitary gland. This condition was first described in 1932 however the exact pathogenesis, diagnostic plan and appropriate treatment regimen are still under dispute. Although, all breeds of horses and both sexes... 

The most common secretory neoplasm of the anterior pituitary gland is a prolactin-secreting adenoma (prolactinoma). An early symptom of prolactin excess is a milky discharge from the breasts. Because hyperprolactinemia may suppress the secretion of gonadotropic hormones (e.g., LH, FSH), menstrual irregularity, amenorrhea, and infertility may occur in women. In men, gonadotropic hormone dysfunction may lead to reduced libido, sexual impotence, and infertility. 

A direct regulatory role for endocannahinoids in normal human anterior pituitary gland and pituitary adenomas has also been postulated (Fagotto et al. 2001). Pituitary adenomas had higher 2VEA and 2-AG concentrations, pointing to a role for endocannahinoids in the development of pituitary adenomas too. 

Fagotto U, Marsicano G, Fezza F, Theodoropoulou M, Grubler Y Arzberger T, Milone A, Losa M, Di Marzo V, Lutz B, Stalla GK (2001) Normal human pituitary gland and pituitary adenomas express cannabinoid receptor type 1 and synthesise endogenous cannabinoids first evidence for a direct role of cannabinoids on hormone modulation at the human pituitary level. J Clin Endocrinol Metab 86 2687-2696... 

Transsphenoidal pituitary surgery is the treatment of choice for TSH-secreting adenomas. Pituitary gland irradiation is often given following surgery to prevent tumor recurrence. Bromocriptine has been used to treat tumors that co-secrete prolactin. 

Cushing syndrome is a rare condition in which elevated levels of cortisol are present in the patient for an extmded period of time (hypercortisolism). Typically, it affects those betweoi the ages of 20 and 50 years. On rare occasions, this disease may result from an inherited condition, which leads to growth of adenomas in endocrine glands, such as the adrenal, parathyroid, pancreas or pituitary glands. 

Pituitary adenomas presenting in the nasal cavity, paranasal sinuses, and nasopharynx are distinctly unusual and can be divided into two types invasive and ectopic.Invasive sinonasal pituitary adenomas are secondary to downward proliferation of a primary sellar tumor. This event occurs in about 2% of all sellar tumors.Ectopic adenomas are those that arise from aberrant embryogenesis of the pituitary gland. 

Lloyd RV, Chandler WF, Kovacs K, et al. Ectopic pituitary adenomas with normal anterior pituitary glands. Am J Surg Pathol. 1986 10(8) 546-552. 

Wahlstrom, T., Stenman, U.H., Lundqvist, C., Tanner, P., Schroder, J., and Seppala, M., 1981, The use of monoclonal antibodies against human chorionic gonadotropin for immunoperoxidase staining of normal placenta, pituitary gland, and pituitary adenomas. J. Histochem. Cytochem. 29 864-865. 

In the studies of long-term exposure of rats to both triphenyltin hydroxide and bis(tributyltin)oxide, most of the tumors were found in endocrine glands. In addition to the pituitary adenomas associated with bis(tributyltin)oxide and triphenyltin hydroxide, there was also an increased incidence of pheochromocytomas of the adrenal gland, parathyroid carcinomas and pancreatic adenocarcinomas in animals from at least one sex. Triphenyltin hydroxide was associated with an increased incidence of testicular Leydig cell tumors in male rats at the highest dose. Hepatic tumors were found in male and female mice following 80 weeks of triphenyltin hydroxide administration. 

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