Thyroid Diseases by Paolo Vitti & Laszlo Hegedüs

Author:Paolo Vitti & Laszlo Hegedüs
Language: eng
Format: epub
Publisher: Springer International Publishing, Cham

Acquired

Neoplasias, affecting the hypothalamus-pituitary region as well as therapeutic interventions on sellar and extrasellar tumor masses (i.e., surgery and radiotherapy), represent the most frequent causes of acquired CH. In particular, pituitary macroadenomas may induce hypopituitarism by affecting either pituitary cells or the pituitary stalk. In this respect, nonfunctioning pituitary adenomas are the tumors most frequently involved. At presentation, isolated or multiple pituitary deficits are diagnosed in 62% of patients with pituitary nonfunctioning macroadenomas, with CH found in 27% of them (Ferrante et al. 2008; Dekkers et al. 2008). The risk and extent of postsurgical hypopituitarism depend on tumor size, tumor extension, and the experience of the surgeon. In particular, new pituitary hormone deficiency is described in 10% of patients who have undergone pituitary surgery in referral centers, with CH occurring in less than 3% of such cases (Losa et al. 2013).

Craniopharyngiomas are typically slowly growing extrasellar tumors, and visual field defects and hypopituitarism are the most common presenting clinical manifestations. In children, GH deficiency is the most common pituitary deficit diagnosed at presentation (up to 100% of patients), followed by TSH deficiency (up to 25% of patients). In adults, CH has been described in 40% of cases, growth hormone deficiency in 80–90% of cases, gonadotropin deficiency in 70% of patients, and ACTH in 40% of patients (Karavitaki et al. 2005, 2006; Muller 2014). Surgical intervention is associated with hypopituitarism in the majority of patients with craniopharyngiomas, with CH reported in 40 to 95% of cases (Karavitaki et al. 2006; Muller 2014).

Importantly, hypopituitarism may occur in patients who undergo neurosurgical intracranial procedures for conditions other than pituitary tumors. In this setting, the main pituitary hormone deficiencies are related to ACTH, GH, and LH/FSH insufficiency and only rarely to TSH insufficiency (Fleck et al. 2013).

Direct and indirect irradiation of the hypothalamic-pituitary axis may cause hypopituitarism. The risk of developing CH is related to both the effective dose given to the area and the total radiation dose delivered (Kanumakala et al. 2003; Schmiegelow et al. 2003). Radiation-induced CH occurs in patients who undergo radiotherapy, not only for pituitary tumors and craniopharyngiomas but also in 10–50% of patients irradiated for nasopharyngeal or paranasal sinus tumors (Samaan et al. 1987; Ratnasingam et al. 2015) and in 12–65% of patients irradiated for any site brain tumors (Constine et al. 1993; Kyriakakis et al. 2016). Unfortunately, data on the long-term effects on hypothalamic-pituitary function of proton beam therapy – whether by Leksell Gamma Knife or stereotactic linear accelerator – are still scarce and inconclusive. However, recent findings suggest that hypopituitarism (including CH) occurs even after these new irradiation methods (Xu et al. 2013). Analyses of the effects of Leksell Gamma Knife on pituitary function in a series of patients affected with Cushing’s disease have demonstrated that new pituitary deficiency occurs in 58% of patients, with a latency of up to 160 months after radiation delivery. The most commonly deficient endocrine axis was the GH (33%) followed by the gonadotroph axis (28 %). Of interest, TSH deficiency was

Download

Copyright Disclaimer:
This site does not store any files on its server. We only index and link to content provided by other sites. Please contact the content providers to delete copyright contents if any and email us, we'll remove relevant links or contents immediately.