Growth hormone releasing hormone excess and blockade in X-LAG syndrome.
Daly, Adrian Francis ; ; et al
in Endocrine-related cancer (2016)
X-linked acrogigantism (X-LAG) syndrome is a newly-described form of inheritable pituitary gigantism that begins in early childhood and is usually associated with markedly elevated growth hormone (GH) and ... [more ▼]
X-linked acrogigantism (X-LAG) syndrome is a newly-described form of inheritable pituitary gigantism that begins in early childhood and is usually associated with markedly elevated growth hormone (GH) and prolactin secretion by mixed pituitary adenomas/hyperplasia. Microduplications on chromosome Xq26.3 including the GPR101 gene cause X-LAG syndrome. In individual cases random GH-releasing hormone (GHRH) levels have been elevated. We performed a series of hormonal profiles in a young female sporadic X-LAG syndrome patient and subsequently undertook in vitro studies of primary pituitary tumor culture following neurosurgical resection. The patient demonstrated consistently elevated circulating GHRH levels throughout preoperative testing, which was accompanied by marked GH and prolactin hypersecretion; GH demonstrated a paradoxical increase following TRH administration. In vitro, the pituitary cells showed baseline GH and prolactin release that was further stimulated by GHRH administration. Co-incubation with GHRH and the GHRH receptor antagonist, acetyl-(D-Arg(2))-GHRH (1-29) amide, blocked the GHRH-induced GH stimulation; the GHRH receptor antagonist alone significantly reduced GH release. Pasireotide, but not octreotide, inhibited GH secretion. A ghrelin receptor agonist and an inverse agonist led to modest, statistically significant increases and decreases in GH secretion, respectively. GHRH hypersecretion can accompany the pituitary abnormalities seen in X-LAG syndrome. These data suggest that the pathology of X-LAG syndrome may include hypothalamic dysregulation of GHRH secretion, which is in keeping with localization of GPR101 in the hypothalamus. Therapeutic blockade of GHRH secretion could represent a way to target the marked hormonal hypersecretion and overgrowth that characterizes X-LAG syndrome. [less ▲]Detailed reference viewed: 37 (16 ULg)
Cabergoline in the treatment of hyperprolactinemia: a study in 455 patients.
; ; et al
in Journal of Clinical Endocrinology and Metabolism (1999), 84(7), 2518-22
Cabergoline is a new long-acting dopamine agonist that is very effective and well tolerated in patients with pathological hyperprolactinemia. The aim of this study was to examine, in a very large number ... [more ▼]
Cabergoline is a new long-acting dopamine agonist that is very effective and well tolerated in patients with pathological hyperprolactinemia. The aim of this study was to examine, in a very large number of hyperprolactinemic patients, the ability to normalize PRL levels with cabergoline, to determine the effective dose and tolerance, and to assess the effect on clinical symptoms, tumor shrinkage, and visual field abnormalities. We also evaluated the effects of cabergoline in a large subgroup of patients with bromocriptine intolerance or -resistance. We retrospectively reviewed the files of 455 patients (102 males and 353 females) with pathological hyperprolactinemia treated with cabergoline in 9 Belgian centers. Among these patients, 41% had a microadenoma; 42%, a macroadenoma; 16%, idiopathic hyperprolactinemia; and 1%, an empty sella. The median pretreatment serum PRL level was 124 microg/L (range, 16-26,250 microg/L). A subgroup of 292 patients had previously been treated with bromocriptine, of which 140 showed bromocriptine intolerance and 58 showed bromocriptine resistance. Treatment with cabergoline normalized serum PRL levels in 86% of all patients: in 92% of 244 patients with idiopathic hyperprolactinemia or a microprolactinoma and in 77% of 181 macroadenomas. Pretreatment visual field abnormalities normalized in 70% of patients, and tumor shrinkage was seen in 67% of cases. Side effects were noted in 13% of patients, but only 3.9% discontinued therapy because of side effects. The median dose of cabergoline at the start of therapy was 1.0 mg/week but could be reduced to 0.5 mg/week once control was achieved. Patients with a macroprolactinoma needed a higher median cabergoline dose, compared with those with idiopathic hyperprolactinemia or a microprolactinoma: 1.0 mg/week vs. 0.5 mg/week, although a large overlap existed between these groups. Twenty-seven women treated with cabergoline became pregnant, and 25 delivered a healthy child. One patient had an intended abortion and another a miscarriage. In the patients with bromocriptine intolerance, normalization of PRL was reached in 84% of cases, whereas in the bromocriptine-resistant patients, PRL could be normalized in 70%. We confirmed, in a large-scale retrospective study, the high efficacy and tolerability of cabergoline in the treatment of pathological hyperprolactinemia, leaving few patients with unacceptable side effects or inadequate clinical response. Patients with idiopathic hyperprolactinemia or a microprolactinoma, on average, needed only half the dose of cabergoline as those with macroprolactinomas and have a higher chance of obtaining PRL normalization. Cabergoline also normalized PRL in the majority of patients with known bromocriptine intolerance or -resistance. Once PRL secretion was adequately controlled, the dose of cabergoline could often be significantly decreased, which further reduced costs of therapy. [less ▲]Detailed reference viewed: 77 (2 ULg)