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Pituitary incidentalomas
No full textThe widespread use of sensitive neuroradiological imaging studies (i.e. computed tomography scan and magnetic resonance imaging) over the last years lead to the diagnosis of an increased number of asymptomatic pituitary lesions. The management of these so-called "pituitary incidentalomas" is still controversial, due to the limited data so far available on both the clinical relevance and the natural history of such incidentally discovered pituitary masses. Most pituitary incidentalomas are less than 1 cm in diameter (microincidentalomas) and are pituitary adenomas. Although these tumours are in general hormonally inactive, all the patients with incidentalomas should be screened for pituitary hypo- or hyper-function. Macroincidentalomas have greater growth potential and, when associated with hypopituitarism and/or visual disturbances, should be surgically removed. Conversely, incidentalomas not associated with hormonal alterations and dimensionally stable could be managed conservatively. This review will focus on the last data on the natural history and clinical management of pituitary incidentalomas
Medical management of thyrotropin-secreting pituitary adenomas
No full textThyrotropin-secreting pituitary tumors (TSH-omas) are a rare cause of hyperthyroidism and account for less than 1% of all pituitary adenomas. It is however noteworthy that the number of reported cases tripled in the last years as a consequence of the routine use of ultrasensitive immunometric assays for measuring TSH levels. Contrary to previous RIAs, ultrasensitive TSH assays allow a clear distinction between patients with suppressed and those with non-suppressed circulating TSH concentrations, i.e. between patients with primary hyperthyroidism (Graves' disease or toxic nodular goiter) and those with central hyperthyroidism (TSH-oma or pituitary resistance to thyroid hormone action). Failure to recognize the presence of a TSH-oma may result in dramatic consequences, such as improper thyroid ablation that may cause the pituitary tumor volume to further expand. The medical treatment of TSH-omas mainly rests on the administration of somatostatin analogs, such as octreotide and lanreotide. In fact, administration of dopamine agonists failed to persistently block TSH secretion in almost all patients and caused tumor shrinkage only in those with combined hypersecretion of TSH and PRL. On the contrary, somatostatin analogs were effective in reducing TSH and α-subunit secretion in more than 90% of cases with consequent normalization, of FT4 and FT3 levels and restoration of the euthyroid state in the majority of them. In about one third of patients, a clear shrinkage of tumor mass and vision improvement could be demonstrated. Tachyphylaxis, cholelithiasis and carbohydrate intolerance occurred in a minority of treated patients. Whether somatostatin analog treatment may be an alternative to surgery and/or irradiation in patients with TSH-oma remains to be established. Nonetheless, the long-acting somatostatin preparations represent a useful tool for long-term treatment of such a rare pituitary tumors
Thyrotropinomas
No full textThyrotropinomas are easily recognized, owing to the availability of ultrasensitive thyropin immunometric assays. These methods allow a clear distinction between patients who have suppressed and those who have nonsuppressed circulating thyrotropin concentrations. In the latter, it is mandatory to perform a differential diagnosis, as the management of the two disorders is completely different, and failure to recognize the presence of a thyrotropinoma may result in dramatic consequences. Adenomectomy is the firstline treatment of thyrotropinomas, followed by irradiation in the case of surgical failure. Medical treatment with somatostatin analogs is effective in reducing thyrotropin secretion in more than 90% of cases
Mutations of LH and FSH receptors
No full textGonadotropins control male and female gonadal function by acting through specific receptors. The recent description of several mutations in LH and FSH receptors has significantly improved our understanding of the pathophysiology of several sexual disorder. Both gain- and loss-of-function germline mutations leading to constitutive receptor activation or to hormone resistance have been described. The clinical impact of these mutant receptors can be markedly different, depending upon the sex of the affected patient and the degree of functional alteration. Numerous mutations were described in LH receptor gene. Constitutive activation of this receptor leads to male-limited precocious pseudopuberty, whereas hypergonadotropic hypogonadism is the clinical phenotype of LH resistance. On the other hand, few mutations of FSH receptor were described so far. Inactivating mutations of FSH receptor are involved in some cases of hypergonadotropic hypogonadism with a more severe impairment of fertility in female patients. Only one gain-of-function mutation of FSH receptor was reported to maintain fertility in one hypophysectomized man. This review is focused on the known genetic alterations of gonadotropic receptors in humans and their impact on male sexual differentiation and fertility
Central hypothyroidism: consequences in adult life
No full textCentral hypothyroidism (CH) is a rare cause of hypothyroidism, generally due to either pituitary or hypothalamic defects. On the basis of its etiology, it is possible to distinguish acquired and hereditary forms. Hereditary CH can be isolated or associated with combined pituitary hormone deficiency (CPHD). In the former case, alterations of only two genes, TSHbeta and the TRH receptor, have so far been described as responsible for the disorder. In hereditary CH associated with CPHD, inactivating mutations of different pituitary transcription factors (HESX1, PROP-1, POU1F1) have been found involved in the pathogenesis of the disease. Finally, an association between CH and severe obesity has been described in patients with leptin receptor (Leptin-R) mutations. The clinical consequences of CH in adult life vary greatly depending on the etiology, the severity of the thyroid impairment, the extent of the associated hormone deficiencies, and the age of the patient at the time of the onset of the disease. In general, acquired CH is less severe than the congenital form because of the constitutive activity of the wild-type TSH-receptor. Symptoms and signs of thyroid insufficiency are usually milder than those of primary hypothyroidism, and goiter is always absent. In CPHD, most patients have other endocrine manifestations of the disease (growth failure, delayed puberty, adrenal insufficiency, diabetes insipidus) that lead them to seek medical attention before the hypothyroidism becomes severe. Early diagnosis of the congenital form by neonatal screening for hypothyroidism is strongly recommended in order to avoid cretinism. Replacement therapy with L-thyroxine administration has to be established as soon as possible
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