I Shimon, X Yan, S Melmed (Univ of California, Los Angeles)
Human Fetal Pituitary Expresses Functional Growth Hormone-Releasing Peptide Receptors. J Clin Endocrinol
Metab 83:174-178, 1998.
Background- The synthetic hexapeptide (GH)-releasing peptide (GHRP) induces a dose-dependent release of GH in humans and animals through a specific receptor in the hypothalamus and pituitary glands.
Campino C, Torres C, Ampuero S, et al (Pontificia Universidad Catolica de Chile, Casilla; Instituto Chileno de Medicina Reproductiva, Santiago, Chile)
Bioactivity of Prolactin Isoforms: Lactation and Recovery of Menses in Nursing Women.
Hum Reprod 14; 898-905, 1999
Background : Among women, breastfeeding may coexist with amenorrhea or with normal menstrual cycles. The factors associated with the resumption of menstrual cycles during lactation are not well understood. Whether differences in plasma prolactin (PRL) isoforms relate to the resumption of menses during lactation by comparing PRL isoforms between amenorrheic and cycling nursing women was examined.
Conclusions: The results demonstrate that lactation in the presence or absence of menses is associated with differences in plasma BIO-PRL and in the presence of particular PRL isoforms. The main difference between amenorrheic and cycling nursing women was the presence of BIO-PRL eluting at pH 7 to 6.1, with a high BIO/IR (Immunoreceptive) ratio exclusively in the amenorrheic nursing women.
Barkan AL, Chandler WF (Univ of Michigan, Ann Arbor)
Giant Pituitary Prolactinoma with Falsely Low Serum Prolactin: The Pitfall of the “High-Dose Hook Effect” : Case Report.
Neurosurgery 42: 913-916, 1998
Background : In most clinical laboratories, current practice is to measure prolactin using 2-site monoclonal immunoradiometric assay (IRMA) or chemiluminometric assay (ICMA). Though these assays are more rapid, accurate, and specific than the earlier radioimmunoassays, they have a pitfall that may severely compromise their performance and provide a grossly accurate measure of prolactin excess.
Conclusion: Clinicians should consider the presence of a high-dose hook effect in all patients with pituitary adenomas larger than 3 cm and normal serum prolactin concentration. Subsequent assay of diluted serum will reliably demonstrate this phenomenon, enabling correct diagnosis and treatment.
Verhelst J, Abs R, Maiter D, et al (Middelheim Ziekenhuis, Antwerp, Belgium; Universitair Ziekenhuis, Antwerp; Cliniques Universitaires St-Luc, Brussels, Belgium; et al)
Cabergoline in the Treatment of Hyperprolactinemia: A Study in 455 Patients.
J Clin Endocrinol Metab 84:2518-2522, 1999.
Background: Cabergoline is a new long-acting dopamine agonist that is being used in the treatment of patients with pathologic hyperprolactinemia. It appears to be well-tolerated and very effective against the clinical symptoms and visual field abnormalities and in shrinking the tumor. Cabergoline’s longer half-life and increased patient tolerability seem to give it several advantages over bromocriptine. However, few clinical studies have been done on this drug. The experience of a group of patients with pathologic hyperprolactinemia treated with cabergoline, and a subgroup treated with cabergoline who were intolerant of or resistant to bromocriptine, was examined.
Results : Serum PRL levels returned to normal for 86% of all patients treated with cabergoline, specifically for 92% of the patients with idiopathic hyperprolactinemia or microprolactinomas, and for 77% of aptietns with macroadenomas. Serum PRL levels were normalized for 70% of the bromocriptine-resistant and 84% of the bromocriptine-intolerant patients. Visual field abnormalities evident before cabergoline treatment were normalized for 70% of patients. For 67% of the patients, tumor shrinkage was noted.
Although side effects were experienced by 13% of patients, only 3.95 discontinued use of cabergoline. In 89% of the women (227 of 254), the menstrual cycle returned to normal, and 27 of the patients became pregnant, with 25 healthy deliveries, 1 elective abortion, and 1 miscarriage.
Conclusions- Cabergoline demonstrated a high degree of efficacy and tolerability in this large-scale study. There were few instances of unacceptable side effects or inadequate clinical response. Cabergoline was highly effective in normalizing PRL secretion in the total group and among patients intolerant of or resistant to bromocriptine. The cost of therapy could be reduced, since dosage could be lowered significantly once PRL secretion was under control.
Freda et al remind us that pergolide is also an excellent treatment for prolactinomas, even if it is not FDA-approved for this use.
Another nice series recently reported was that of patients with cysts occurring in the hypothalamus (21 craniopharyngiomas, 26 Rathke’s cleft cysts, and 5 arachnoid cysts) seen at the University of Toronto. The fact that many of these patients had hyperprolactinemia (38% of craniopharyngiomas, 46% of Rathke’s cleft cysts, and 20% of arachnoid cysts.
Landolt AM, Haller D, Lomax N, et al (Klinik im Park, Zurich, Switzerland)
Octreotide May Act As a Radioprotective Agent in Acromegaly
J Clin Endocrinol Metab 85: 1287-1289, 2000
Patients with acromegaly can be treated by:
(2) Antisecretory drugs (octreotide)
(3) Radiation therapy
in order to decrease circulating levels of GH and insulin-like growth factor I(IGF-I) to normal levels.
This retrospective study was conducted on 31 patients with acromegaly to determine the effect of octreotide therapy on the results of stereotactic surgery.
It was found that octreotide therapy has a radioprotective effect on the pituitary adenomas of patients, with acromegaly. Hence, it is recommended that patients should not receive octreotide, when stereotactic radiosurgery is done. Octreotide can be started or resumed after completion of radiosurgery.
Kojima M, Hosoda H, et al (Natl Cardiovascular Ctr Research Inst, Osaka, Japan; Miyazaki Med College, Japan)
Ghrelin is a Growth-Hormone-Releasing Acylated Peptide From Stomach
Nature 402: 656-660, 1999
Release of growth hormone (GH) from the pituitary is stimulated by GH secretagogues (GHSs) that act through a G-protein -coupled receptor (GHS-R)
Ghrelin found in the rat stomach, function as an endogenous ligand specific for GHS-R
GH releasing hormone (GHRH) had no effect on cells potently induced by ghrelin to increase intracellular calcium concentration; ghrelin inhibited the action of an antagonist, raising calcium concentration back to preantagonist levels.
In humans, the GH-releasing activity of ghrelin compared favourably with GHRH. When ghrelin was injected into anaesthetized rats, only GH concentrations rose to maximal levels, indicating ghrelins specifity for GH.
The authors concluded that release of GH from the pituitary may be regulated by both hypothalamus GHRH and ghrelin.
Beuschlein F,Strasburger CJ et al (Klinikum der Albert Ludwigs-Universitat Freiburg, Germany; Klinikum Innenstadt der Ludwig-Maximilians-Universitat, Munich; German Cancer Research Ctr, Heidelberg, Germany)
Acromegaly caused by secretion of growth hormone by a non-Hodgkin’s lymphoma.
N Engl J Med 342: 1871-1876, 2000
This is a case report of a patient with recurrent non-Hodgkin’s lymphoma and acromegaly resulting from ectopic production of GH by the lymphoma. The lymphoma was strongly immunoreactive to GH