Ectopic ACTH syndrome

Ectopic ACTH syndrome represents a cancer-induced amplification of a property [proopiomelanocortin (POMC) peptides production] normally present in the cells from which the cancer originated but with aberrant posttranslational processing of POMC resulting in a greatly elevated secretion of ACTH precursors. The classic ectopic ACTH-producing tumors described in the 1960s were highly malignant but more recently slowly growing tumors such as carcinoids are reported with increasing frequency. Clinical features of patients with ectopic ACTH were analyzed, including biochemical abnormalities, plasma ACTH, cortisol and urinary steroids. Dynamic tests such as high-dose dexamethasone suppression, metyrapone and ovine-CRH (oCRH) stimulation were explored, as well as inferior petrosal sinus ACTH sampling before and after oCRH. Among the tumor markers examined, elevation of ACTH precursors was uniformly present followed by increased output of calcitonin, gut hormones, oncofetal and placental hormones in decreasing order. Since more than 90% of ectopic ACTH tumors are neuroendocrine in nature exhibiting APUD characteristics, their 2 markers, neuron-specific enolase and chromogranins are very useful. The imaging procedures for localization of the tumor ranged from chest X-rays to computed tomography and magnetic resonance of the chest and abdomen. Abdominal ultrasonography was also useful. Finally somatostatin receptor scintigraphy permitted demonstration of unrecognized tumors and/or metastases, even when the tumors were occult. The ACTH content, immunostaining for APUD markers and altered POMC processing were evaluated in ectopic tumors and/or metastases. Occult ectopic ACTH syndrome of more than 4–6 months of symptoms without the emergence of an obvious source was reviewed. Since the tumors are often clinically and biochemically undistinguishable from pituitary-dependent Cushing's disease, inferior petrosal sinus sampling for ACTH after oCRH stimulation established the diagnosis in over 90% of the cases. 60% of the occult tumors were thoracic carcinoids (3/4 bronchial carcinoids), followed by small cell lung cancer and pancreatic neuroendocrine tumors. In 12% the primary etiology was not detected. The rare syndrome of ectopic CRH syndrome (6 published cases) leading to excessive stimulation of the pituitary which became hyperplastic and secreted excessive amounts of ACTH is discussed. Finally, the 12 published cases and 1 unreported patient with ectopic CRH-ACTH tumors were reviewed, the majority being metastatic small cell lung carcinomas, bronchial and thymic carcinoids.     

The met-enkephalin analog FK 33-824 directly inhibits ACTH release by the rat pituitary gland in vitro

Systematic administration of the enkephalin analog FK 33-824 was previously shown to stimulate PRL secretion and to inhibit ACTH secretion in man. Naloxone prevented the effect on PRL release, but not on ACTH release. In this study, the direct action of this analog on hormone release by rat anterior pituitary lobes $\text{in}$$\text{vitro}$ were investigated. 1 uM FK 33-824 inhibited basal ACTH secretion by anterior pituitary glands in vitro, while 0.1 uM and 1 uM attenuated the lysine vasopressin stimulated ACTH release. Naloxone did not reverse the inhibitory action of the analog on ACTH release. β-Endorphin (0.01 - 1 uM) did not directly affect ACTH release. Basal and dopamine-induced inhibition of PRL release by anterior pituitary glands was neither influenced by FK 33-824 (0.1 and 1 uM), nor by β-endorphin (0.1 and 1 uM) with or without bacitracin. This study shows that the long-acting met-enkephalin analog FK 33-824 differentially affects PRL and ACTH secretion by the pituitary gland. It seems to stimulate PRL release at a suprapituitary site and this action probably involves u opiate receptors, because naloxone prevents these stimulatory effects. The inhibitory effect of FK 33-824 on ACTH release, however, is mediated via a direct effect at the pituitary level, which does not involve u receptors, as naloxone did not prevent this effect. In this respect, its action differs from that of β-endorphin, which does not directly affect ACTH release by the anterior pituitary gland.     

Experience with selective venous sampling in diagnosis of ACTH-dependent Cushing's syndrome.

Twenty-three patients with adrenocorticotrophic hormone-(ACTH)-dependent Cushing''s syndrome were subjected to selective venous catheterisation and sampling for ACTH on a total of 26 occasions. Out of 10 patients with pituitary-dependent disease, nine had raised ACTH concentrations in one or both high internal jugular vein samples. Eight patients had 11 proved sites of ectopic hormone production: of these, six were correctly identified by the sampling technique, and in four of them this was the only accurate method of localisation. The results of one catheterisation were misleading, and on 10 occasions they were inconclusive; five patients remained undiagnosed by any method. Overall, 15 of the 26 catheterisations provided diagnostically valuable information. Selective venous catheterisation and sampling for ACTH is effective in confirming a pituitary source of the hormone and may be valuable in locating the source of ectopic ACTH production in some cases.     

Venous Sampling for Cushing Disease: Comparison of Internal Jugular Vein and Inferior Petrosal Sinus Sampling

Objective: Because magnetic resonance imaging (MRI) fails to detect many adrenocorticotropic hormone (ACTH)-secreting pituitary adenomas, inferior petrosal sinus sampling (IPSS) is considered the gold standard to differentiate Cushing disease (CD) from ectopic ACTH secretion syndrome (EAS). Some authors have suggested internal jugular vein sampling (IJVS) as an alternative to IPSS.Methods: We simultaneously compared IJVS to IPSS in 30 consecutive patients referred for ACTH-dependent Cushing syndrome and equivocal MRI exams. Five sites were simultaneously sampled in each patient (right and left IPS, right and left IJV, and femoral vein) before and after the administration of corticotrophin-releasing hormone or desmopressin. The test was considered consistent with CD when the IPS to peripheral ratio was >2 at baseline or >3 after stimulus and the IJV to peripheral ratio was >1.7 at baseline or >2 after stimulus.Results: In 27 of 30 patients, IPSS results were consistent with a central source of ACTH. Two of the other 3 patients had EAS (one lung carcinoid and one occult), and 1 patient had pathology-proven CD. The sensitivity of IPSS was 96.4%. Only 64.2% of these patients had results meeting criteria for a central source of ACTH by IJVS criteria. Twenty patients with centralizing IPPS have undergone pituitary surgery. Of these, the central origin of excessive ACTH was confirmed with certainty in 16 patients. Among these 16 patients, the IPSS sensitivity was 93.8%, whereas 5 patients had false-negative IJVS (68.7% sensitivity).Conclusion: These results do not support the routine use of IJVS in establishing if the pituitary is the source of excessive ACTH.Abbreviations:ACTH = adrenocorticotropic hormoneCD = Cushing diseaseCRH = corticotrophin-releasing hormoneCS = Cushing syndromeDDAVP = desmopressinEAS = ectopic ACTH secretionIJVS = internal jugular vein samplingIPSS = inferior petrosal sinus samplingJVS = jugular venous samplingMRI = magnetic resonance imaging     

Plasma immunoreactive corticotrophin and lipotrophin in Cushing's syndrome and Addison's disease.

Plasma immunoreactive corticotrophin (ACTH) and lipotrophin (LPH) were measured in patients with raised circulating concentrations from a pituitary or an ectopic source. They were measured again in seven patients after they had received hydrocortisone. Plasma ACTH concentrations were higher than LPH concentrations in patients with a pituitary source of their hormones, whereas this relation was reversed when the source was ectopic. After hydrocortisone administration the half life of immunoreactive ACTH was 40 minutes and that of LPH 95 minutes, resulting in a reversal of the normal relation of ACTH to LPH. The use of two antisera with different specificities for measuring LPH has further shown that pituitary LPH differs from ectopic LPH. Relatively less gamma-LPH than beta-LPH was produced from ectopic sources, the relation being reversed in patients with a pituitary source for their raised concentrations. Measuring plasma LPH as well as ACTH might therefore help in deciding whether a patient with Cushing''s syndrome has a pituitary or ectopic source of ACTH, which sometimes presents a difficult clinical problem.     

Allometric relations of total volumes of prolactin cells and corticotropic cells to body length in the annual cyprinodont Cynolebias whitei: effects of environmental salinity,stress and ageing

Summary An analysis of the allometric relations of the total volumes occupied by prolactin (PRL) and corticotropic (ACTH) cells (PRL volume and ACTH volume, respectively) to body length and a study of the immunocytochemical staining intensity of PRL and ACTH cells were used to determine the differences in activity of PRL and ACTH cells in freshwater-reared and in saltwater-reared Cynolebias whitei during the entire lifespan of this annual cyprinodont fish. An inflection in the allometric relation of PRL volume to body length was observed in fish of one-week old. The relatively large PRL volume in younger fish may be related to PRL cell activity before hatching. No inflections were observed in the allometric relations of PRL volume and ACTH volume to body length at the onset of maturation and the onset of ageing, indicating that the increased pituitary growth in maturing and ageing C. whitei is not the result of changes in PRL or ACTH cells. The slope of the allometric relation of PRL volume to body length in freshwater-reared fish was significantly steeper than the slope in saltwater-reared fish. The PRL volume in adult freshwater-reared fish was eight times larger than that in saltwater-reared fish of the same length. The intensity of immunocytochemical staining of saltwater PRL cells was significantly reduced. These volumetric and staining differences correspond to the low functional demand put upon PRL cells in saltwater-adapted fish. In contrast, the slope of the allometric relation of ACTH volume to body length and the intensity of immunocytochemical staining of ACTH cells were similar in freshwater-reared and in saltwater-reared fish. It is concluded that the functional demand put upon ACTH cells is similar in freshwater-reared and saltwater-reared C. whitei; the involvement of ACTH cells in the osmoregulation of the fish in both environments is similar.     

Catecholaminergic control of plasma growth hormone and thyrotropin levels in hypophysectomized rats bearing ectopic pituitary transplants

Transplantation of the anterior pituitary to an ectopic site leads to stimulation of PRL secretion and suppression of the release of other adenohypophyseal hormones. We have previously reported that precursors and blockers of catecholamine synthesis can affect PRL release from the ectopic pituitary. In the present study we have measured the effects of L-3,4-dihydroxyphenylalanine (DOPA), DL-threo-dihydroxyphenylserine (DOPS), alpha-methyl-para-tyrosine (alpha-mpt) and diethyldithiocarbamate (ddc) on plasma growth hormone (GH) and thyrotropin (TSH) levels in hypophysectomized rats with pituitary transplants under the renal capsule. In these animals, peripheral plasma GH levels were elevated by a precursor (DOPA) and reduced by a blocker (alpha-mpt) of catecholamine synthesis. Plasma TSH levels were increased by a precursor (DOPS) and reduced by a blocker (ddc) of norepinephrine synthesis. We suspect that GH and TSH present in the circulation of pituitary-grafted animals were derived, in part, from the ectopic pituitary tissue and suggest that the small but detectable secretion of hormones other than PRL in this animal model is under the control of endogenous catecholamines.     

Prolactin control of growth and prolactin autoregulation in cultured human pituitary cells

A human pituitary cell line (18-54,SF) grows in serum-free medium and secretes prolactin (PRL). Autoregulation of pituitary cell growth and PRL production by exogenously supplied ovine PRL (oPRL) was investigated. Human PRL (hPRL) and oPRL stimulated pituitary cell growth up to 92% and 85%, respectively, at hPRL and oPRL additions of 100-1,000 ng/ml. Short-term (1 h) incubation of the cells with oPRL decreased hPRL secretion from the cells by 72% at 10 ng/ml addition. Intracellular hPRL was stimulated under the same conditions by 50-275% at oPRL concentrations of 10-1,000 ng/ml. Long-term (10 days) incubation of the cells with oPRL had no significant effect on extracellular or intracellular hPRL production. These data suggest that the pituitary gland can serve as a primary feedback site and that PRL can autoregulate its own production as well as affect the growth of pituitary cells.     

Development and retention of phenotypically specialized cells in pituitary allografts in the hamster (Mesocricetus auratus)

Summary We used immunohistochemistry to identify cells present in pituitary allografts in the hamster. Hypophyses removed from neonatal hamsters or adenohypophyses removed from adult females were placed beneath renal capsules of hypophysectomized adult females. Serum PRL, LH, and GH concentrations were measured at two, five, and eight weeks after placement of allografts. Allografts were removed after eight weeks and stained for cells containing PRL, LH, FSH, GH, or ACTH. Allografts did not release LH or GH. Those of adult adenohypophyseal tissue released significantly more PRL. The morphology of allografts of neonatal hypophyseal tissue resembled that of the adult adenohypophysis in situ. Lactotrophs, corticotrophs, somatotrophs and LH-cells were observed; very few FSH-cells were present. Allografts of adult adenohypophyseal tissue contained pituitary cells, numerous cavities, often enclosing lymphoid cells, and fibrous tissue. Atypical lactotrophs were the numerically dominant cells in these allografts; all other cells were present. The LH-cells outnumbered FSH-cells. These observations suggest that: (a) development of normal adenohypophyseal morphology can occur in an ectopic position; (b) intracellular hormones are present in cells in an ectopic site; (c) development and retention of intracellular FSH is more dependent on occupation of the normal position of the adenohypophysis than is retention of intracellular LH; and (d) release of PRL occurs from atypical cells in allografts of adult adenohypophyseal tissue.     

Multiple hormone storage by cells of the human pituitary

While immunostaining serial semi-thin sections of acrylic resin-embedded normal human pituitary using antisera to human pituitary hormones, it became clear that several cells were stained by more than one antiserum. The tissue had been surgically excised from a patient with a prolactinoma. The tumor, which was immunoreactive only with antiprolactin antiserum, was distinctly different from the pieces of tissue under study which had normal pituitary architecture and demonstrated immunoreactivity with antisera against all six of the common pituitary hormones. A major immunoelectron microscopic investigation, using immunocolloidal gold and immunoperoxidase methods, revealed cells in which follicle-stimulating hormone (FSH), luteinizing hormone (LH), and prolactin (PRL) were co-localized to the same electron-dense granules. Some similar cells also possessed electron-lucent granules immunoreactive only for anti-PRL antiserum. Adrenocorticotrophic hormone (ACTH) and PRL were also found in the same cell but were very largely localized to separate, morphologically different populations of electron-dense and -lucent storage granules. By employing double immunolabeling, a few granules in the ACTH/PRL cells were shown to be immunoreactive to both anti-ACTH and anti-PRL antisera. The possibility that the multipotential stem cells is discussed.     

Growth hormone is secreted by ectopic pituitary grafts and stimulates maternal behavior in rats

The onset of maternal behavior at parturition in rats is hormonally regulated. Recently, we reported that treatment of behaviorally inexperienced, hypophysectomized (hypox), ovariectomized (ovx) rats with a sequential steroid treatment of progesterone (P) and estradiol (E2), and either ectopic anterior pituitary grafts or prolactin (PRL), stimulated maternal responsiveness toward foster young. That growth hormone (GH) has a number of PRL-like activities led us to ask whether the actions of PRL on maternal behavior were specific to PRL or might be shared by other PRL-like protein hormone, i.e., GH. In Experiment 1 we quantified plasma concentrations of GH and PRL by RIA in groups of hypox female rats that were ovariectomized and treated with a combination of ectopic pituitary grafts (Days 1-23) and Silastic capsules filled with P (Days 1-11) and E2 (Days 11-23). Blood samples were collected from Days 1 to 23 of treatment. Both plasma PRL and GH levels increased after grafting, initially rising 10- to 60-fold by Day 4 and gradually declining throughout the remainder of the 23-day sampling period. Throughout the 3-week period after grafting plasma GH levels were as high or higher than those of PRL. In Experiment 2 the behavioral effects of exogenously administered ovine (o)-GH were measured in groups of hypox, ovx rats that were treated with P and E2 as in Experiment 1. Experimental rats were injected twice daily with 0.25 mg oGH beginning on Day 1. Testing for maternal behavior toward foster young was conducted daily from Day 12 to Day 22. In steroid-treated rats, GH treatment stimulated a more rapid onset of maternal behavior (latencies of 3 vs greater than 10 days for vehicle-injected controls). These data indicate that GH, like PRL, is secreted by ectopic pituitary grafts and is capable of stimulating maternal behavior.     

雌激素诱发大鼠原位与移植垂体催乳素瘤中催乳素基因与TGFα和TGF …

利用本实验室建立的１７β－雌二醇诱致Ｓｐｒａｇｕｅ－Ｄａｗｌｅｙ（ＳＤ）大鼠原位垂体和异体移植于肾囊的垂体同时形成催乳素瘤的动物模型,采用Ｎｏｒｔｈｅｍ印迹杂交方法,我们观察了Ｅ２长期作用（１２０ｄ）后诱发的原位与移植垂体ＰＲＬ瘤中ＰＲＬ基因和两种转化生长因子ＴＧＦα和ＴＧＦβ１基因表达水平的改变。结果表明：在Ｅ２长期作用后,原位垂体与异体移植于肾囊,从而远离下丘脑的垂体均可形成垂体ＰＲＬ瘤;原位     

Ectopic corticotrophin-releasing-factor and growth hormone releasing factor secretion: diagnosis using human pituitary cell culture

Cell culture of human pituitary tissue has been used to diagnose a patient with Cushing's syndrome due to ectopic secretion of corticotrophin-releasing factor (CRF; case 1) and a case of acromegaly associated with ectopic secretion of a growth-hormone releasing factor (GRF; case 2). In both patients a pituitary tumour was not detected. Case 1 had a small cell carcinoma and symptoms of the ectopic ACTH syndrome, but in culture the carcinoma failed to secrete detectable ACTH. However, the culture medium used to maintain this carcinoma in vitro was found to contain a substance which stimulated ACTH secretion by human pituitary corticotrophs in cell culture. Radioimmunoassays and HPLC indicated that this substance had similar elution characteristics to human CRF and cross-reacted with antiserum to ovine CRF. Case 2 was found to have a lung tumour, the removal of which led to regression of her acromegalic symptoms. In culture, this tumour did not secrete GH, but did secrete a GRF. We conclude that the Cushing's syndrome and acromegaly, in cases 1 and 2, respectively, were due to ectopic secretion of CRF and GRF leading to hyperstimulation of the pituitary gland.     

Human prolactin heterogeneity in pituitary effluent blood

We have used column chromatography to study prolactin (PRL) heterogeneity in plasma obtained from the inferior petrosal vein, a sampling site very close to the anterior pituitary gland. Blood specimens were obtained from four hyperprolactinemic subjects over varying time intervals during inferior petrosal vein venography. All patients demonstrated an increase in PRL secretion during the sampling period which was presumably secondary to the mild stress of the procedure. In each study subject there was an increase in the percent and amount of PRL secreted as small PRL (peak III) as the PRL concentration in the inferior petrosal vein increased to a maximum. The percent secreted as intermediate PRL (peak II) fell while the amount either remained constant or increased slightly. The percent and amount eluting as large PRL (peak I) was small and unchanging in patients 1, 2 and 3, despite the increase in total PRL concentration. Patient 4 had an unusual elution pattern in which the 0 minute specimen contained predominantly large PRL. As the total PRL concentration increased the percent and amount eluting as small PRL dramatically increased while the percent eluting as large PRL fell in proportion to the increase of small PRL. Intermediate PRL was virtually absent in this patient. Thus, this study indicates that the increase in PRL concentration during a secretory pulse is primarily from small PRL while the contributions of large and intermediate PRL are modest and variable.     

Effects of oxytocin alone and in combination with selected hypothalamic hormones on ACTH, beta-endorphin, LH and PRL secretion by anterior pituitary cells of cyclic pigs

Oxytocin (OT) is involved in the stimulation of secretion of anterior pituitary hormones in females during the periovulatory and periparturient periods. In the present study we examined the role of OT in control of ACTH, beta-endorphin, LH and PRL secretion in vitro from dispersed anterior pituitary cells collected from gilts during the luteal (Days 10-12; n=6) and follicular (Days 18-20; n=5) phases of the estrous cycle. Isolated anterior pituitary cells (1 x 10(6)/ml) were transferred into 24-well plates, separately for each animal, and were pre-incubated for three days at 37 degrees C in atmosphere of 5% CO(2) and 95% air. The cells which attached to the dishes were incubated (3.5 h, 37 degrees C) in McCoy's medium in the absence (control) or in the presence of the following factors: CRH alone (10(-10), 10(-9), 10(-8), 10(-7) M), OT alone (10(-8), 10(-7), 10(-6) M), LVP alone (10(-7) M), OT (10(-7) M) plus CRH (10(-9) M) and LVP (10(-7) M) plus CRH (10(-9) M) for studying ACTH and beta-endorphin secretion; OT alone (10(-8), 10(-7), 10(-6) M), GnRH alone (100 ng/ml), CRH alone (10(-9) M), OT (10(-7) M) plus GnRH (100 ng/ml) and OT (10(-7) M) plus CRH (10(-9) M) for studying LH and PRL secretion. Concentrations of the studied hormones in media were analyzed by RIA. Oxytocin alone increased ACTH (at doses 10(-7), 10(-6) M), beta-endorphin (at dose 10(-8) M), LH (at dose 10(-8) M) and PRL (at doses 10(-7), 10(-6) M) secretion by pituitary cells isolated only from luteal-phase gilts. None of the studied hormone concentrations in the medium was increased in response to OT when pituitary cells of follicular-phase gilts were examined. Oxytocin in combination with CRH exerted an additive effect on beta-endorphin secretion during the luteal phase. Summarizing, in the present study the stimulatory effect of oxytocin on ACTH, beta-endorphin, LH and PRL secretion by pituitary cells isolated from gilts during the luteal phase was demonstrated. However, the cells collected from follicular-phase gilts appeared to be unresponsive to OT. Moreover, interaction between OT and CRH in affecting beta-endorphin secretion was shown. These results suggest that OT may be transiently involved in the modulation of anterior pituitary hormone secretion in cyclic pigs.     

Immunohistochemical localization of hormones and peptides in the human pituitary cells in a case of hypercortisolism by ACTH secreting microadenoma

This study assesses the action of hypercortisolism on the hormone and peptide periadenoma region of removed ACTH-producing microadenoma. Our findings show that cortisol excess affects both ACTH and GH production, with no immunoreaction for these hormones. The remaining pituitary hormones (TSH, FSH and PRL) and POMC-derived peptides (betaEnd, alphaMSH and betaMSH) were not modified. Likewise, we observed pituitary immunoreactive cells for Neurotensin (NT), Intestinal vasoactive peptide (VIP), Substance P (SP) and Angiotensin-II (Ang-II). The colocalization demonstrated that NT was expressed in thyrotrope and gonadotrope cells, VIP in gonadotrope cells and SP in corticotrope cells. The results about Ang-II were inconclusive. On the other hand, immunoreaction for the NPY and Gal peptides were not present. In the adenomatous cells, the peptide NT is present in ACTH cells as well as SP. These results suggest a peptide regulation of pituitary cells in the pathological state that can differ between normal and tumoural cells of the same pituitary.     

Effect of dexamethasone on the release of pituitary hormones in monolayer cultures of rat pituitary cells

The effect of dexamethasone on the release of ACTH, GH, PRL, LH and TSH was studied in monolayer cultures of rat pituitary cells in 4-hour incubation. With or without the addition of rat hypothalamic extract, the release of GH was significantly inhibited by dexamethasone at concentrations higher than 10(-9) M, although less remarkably than that of ACTH. Intracellular ACTH and GH were unchanged. PRL, LH and TSH were not affected. These results indicate that dexamethasone, when exerted for 4 hours, suppressed the release of GH as well as ACTH, at least in part, at the pituitary level.     

Suppression of the prolactin surges in the pseudopregnant rat by urethane anesthesia

In pseudopregnancy of the rat prolactin (PRL) is released in the form of twice daily surges (nocturnal and diurnal surges). An attempt was made to examine the effects of urethane anesthesia on PRL surges during pseudopregnancy of the rat. In a preliminary study, using the continuous blood sampling method, the nocturnal PRL surge was completely blocked when urethane (1.0g/kg BW) was administered at 0:00 hr. Urethane (1.0g/kg BW) was injected at 0:00 or 12:00 hr, and serum and pituitary PRL concentrations were measured at 6:00 or 18:00 hr, respectively, to study the effects of urethane on nocturnal or diurnal PRL surges. There were no serum PRL surges during either the nocturnal or diurnal periods following urethane injection. The experiment examining pituitary PRL concentration at 6:00 or 18:00 hr confirmed that urethane (1.0g/kg) anesthesia suppressed the release of PRL surge from the pituitary.