Synthetic MIF has no effect on beta-MSH and ACTH hypersecretion in Nelson's syndrome

Corticotroph tumor progression after bilateral adrenalectomy (Nelson's syndrome): systematic review and expert consensus recommendations

BACKGROUND

Corticotroph tumor progression (CTP) leading to Nelson's syndrome (NS) is a severe and difficult-to-treat complication subsequent to bilateral adrenalectomy (BADX) for Cushing's disease. Its characteristics are not well described, and consensus recommendations for diagnosis and treatment are missing.

METHODS

A systematic literature search was performed focusing on clinical studies and case series (≥5 patients). Definition, cumulative incidence, treatment and long-term outcomes of CTP/NS after BADX were analyzed using descriptive statistics. The results were presented and discussed at an interdisciplinary consensus workshop attended by international pituitary experts in Munich on October 28, 2018.

RESULTS

Data covered definition and cumulative incidence (34 studies, 1275 patients), surgical outcome (12 studies, 187 patients), outcome of radiation therapy (21 studies, 273 patients), and medical therapy (15 studies, 72 patients).

CONCLUSIONS

We endorse the definition of CTP-BADX/NS as radiological progression or new detection of a pituitary tumor on thin-section MRI. We recommend surveillance by MRI after 3 months and every 12 months for the first 3 years after BADX. Subsequently, we suggest clinical evaluation every 12 months and MRI at increasing intervals every 2-4 years (depending on ACTH and clinical parameters). We recommend pituitary surgery as first-line therapy in patients with CTP-BADX/NS. Surgery should be performed before extrasellar expansion of the tumor to obtain complete and long-term remission. Conventional radiotherapy or stereotactic radiosurgery should be utilized as second-line treatment for remnant tumor tissue showing extrasellar extension.

Neuropeptide Y in the intermediate lobe of the frog pituitary acts as an alpha-MSH-release inhibiting factor

The presence of neuropeptide tyrosine (NPY) in the intermediate lobe of the frog pituitary was demonstrated using indirect immunofluorescence, the immunogold technique and a specific radioimmunoassay combined with high pressure liquid chromatography (HPLC). A high density of NPY-containing fibers, was found among the parenchymal cells of the intermediate lobe. These fibers originated from the ventral infundibular nucleus, travelled via the median eminence to the pars intermedia. At the electron microscopic level, NPY-like material was found exclusively in nerve fibers where the product of the immunoreaction was associated to dense-core vesicles. High concentrations of NPY-like peptide were found in neurointermediate lobe extracts. After Sephadex G-50 gel filtration the major peak of immunoreactive material appeared to co-elute with synthetic porcine NPY. Conversely, HPLC analysis revealed that the NPY-like peptide of the frog pituitary had a retention time shorter than the porcine NPY. The localization of NPY-like material in the pars intermedia suggested a possible role of NPY in the regulation of melanotropic cell secretion. In fact, graded concentrations of synthetic NPY induced a dose-dependent inhibition of alpha-melanotropin (alpha-MSH) release in vitro. The lack of effect of a dopaminergic antagonist on NPY-induced alpha-MSH release inhibition demonstrated that the local dopaminergic system could not account for the NPY action. These results indicate that NPY located in the hypothalamo-hypophyseal system of the frog may act as a melanotropin-release inhibiting factor.

Effect of Tyr-Pro-Leu-Gly-NH2 on melanotropin-stimulating hormone release in the frog and rat

The tetrapeptide Tyr-Pro-Leu-Gly-NH2 (Tyr-MIFI) has been recently characterized in the hypothalamus and pineal of the rat. Since the concentration of Tyr-MIFI in the brain is increased by pinealectomy and is higher when the animals are in the dark, the possibility that Tyr-MIFI could be a physiological regulator of melanotropin secretion has been investigated. For this study a well-defined perifusion model has been applied, using whole neurointermediate lobes from male frogs (Rana ridibunda Pallas) or male Wistar rats. The amount of alpha-MSH released in the effluent perifusate was measured by means of a sensitive and specific radioimmunoassay method. For concentrations ranging from 10(-10) to 10(-6) M, Tyr-MIFI did not significantly alter the spontaneous release of alpha-MSH in the frog nor did it alter the release of alpha-MSH in the rat. Since it has been recently demonstrated that the tripeptide pGlu-His-Pro-NH2 (mammalian TRH) is a specific MSH-releasing factor in the frog, the possibility that Tyr-MIFI could modulate the response of the intermediate lobe of the frog to TRH has also been investigated. No alteration of TRH-induced alpha-MSH release was observed in the presence of a 100-fold excess of Tyr-MIFI. In addition, Tyr-MIFI was found to be unable to lighten the skin of the frog (Rana pipiens) when applied directly to the pituitary of the darkened animals. Thus these results definitively rule out the possibility that Tyr-MIFI is the melanotropin-release inhibiting factor in the frog or rat.

Similar antagonism of morphine analgesia by MIF-1 and naloxone in Carassius auratus

Prolyl-leucyl-glycinamide (MIF-1), the C-terminal tripeptide of oxytocin, and naloxone were administered intracranially (IC) to goldfish (Carassius auratus) in doses of 0.001, 0.01, 0.1, 1.0 and 10.0 mg/kg and compared to a diluent control group for their ability to reduce the effects of morphine (30 mg/kg IC) in an assay measuring analgesia to electric shock. Threshold levels of pain were determined by the voltage necessary to produce an agitated swimming response (ASR). Both MIF-1 and naloxone were found to significantly reduce the analgesic effects of morphine when compared to the diluent control group. Similar dose-response curves in an apparent sine-wave pattern were noted with both MIF-1 and naloxone when comparisons were made both at 20 minutes after administration of morphine and over the entire 150 minutes of the experiment. The results support the evidence that MIF-1 can act as an opiate antagonist.

ACTH in normal children and children with pituitary and adrenal diseases. I. Measurement in plasma by radioimmunoassay--basal values

Plasma ACTH was measured by radioimmunoassay including preliminary extraction onto adsorbent glass particles. Normal basal values for children 4-16 years of age were 11-82 microgram/ml, corresponding to values found in the literature. Normal values were found in girls with precocious puberty, children with McCune-Albright and Beckwith-Wiedemann's syndrome. Values between 233 and 305 pg/ml were found in untreated children with congenital adrenal hyperplasia. In primary Addison's disease, very high levels (654-1 413 pg/ml) before cortisone therapy and their decline to nearly normal values during therapy are described. ACTH values in a case of pituitary Cushing's syndrome was just above the normal range (104-163 microgram/ml).