Tests of prolactin secretion in diagnosis of prolactinomas

Pharmacokinetics and pharmacodynamics of ropinirole in patients with prolactinomas

AIMS

Treatment of prolactinomas with ergoline dopamine agonists can be complicated by intolerance and resistance. This study investigated the pharmacokinetics and pharmacodynamics of the nonergot dopamine agonist ropinirole, to assess its therapeutic potential as a novel therapy for prolactinomas.

METHODS

Five female subjects with prolactinomas participated in this dose-response study. Subjects received up to three doses of ropinirole (0.5, 1.0 and 2.0 mg), each on separate occasions. Frequent blood samples for prolactin and ropinirole were collected for 24 h following drug administration. Data were analysed using noncompartmental and compartmental pharmacokinetic-pharmacodynamic (PKPD) techniques.

RESULTS

Seven 24-h curves revealed increased systemic drug exposure with increasing ropinirole doses. Ropinirole concentrations peaked at 4.4 ± 2.7 h and exhibited a half-life of 5.8 ± 1.7 h. A dose-dependent prolactin nadir occurred 4.4 ± 1.2 h after drug intake and prolactin concentrations transiently normalized in two of five subjects. PKPD modelling revealed that single-dose PK of ropinirole is dose-independent and can be described with a one-compartment model with linear absorption and elimination. An indirect response model successfully captures the inhibitory effect of ropinirole on prolactin secretion and incorporates time-dependent receptor desensitization for three of five subjects whose prolactin concentrations nadired before ropinirole reached C_max .

CONCLUSIONS

This data-rich study has informed our understanding of the clinical pharmacokinetics and pharmacodynamics of ropinirole, which are successfully captured by the proposed semi-mechanistic PKPD model. This model can be used to further investigate the PKPD of ropinirole and may facilitate the identification of optimal dose regimens for the treatment of prolactinomas and the establishment of a new therapeutic option for patients impacted by this rare disease.

Determination of prolactin: the macroprolactin problem

Serum prolactin is frequently measured when investigating patients with reproductive disorders and elevated concentrations are found in up to 17% of such cases. Clinical laboratories rely predominantly on automated analysers to quantify prolactin levels using sandwich immunometric methodologies. Though generally robust and reliable, such immunoassays are susceptible to interference from a high molecular mass prolactin/IgG autoantibody complex termed macroprolactin. While macroprolactin remains reactive to varying degrees in all prolactin immunoassays, it exhibits little if any biological activity in vivo and consequently its presence is considered clinically irrelevant. Macroprolactinaemia, defined as hyperprolactinaemia due to excess macroprolactin with normal concentrations of bioactive monomeric prolactin, may lead to misdiagnosis and mismanagement of hyperprolactinemic patients if not recognised. Current best practice recommends that all sera with elevated total prolactin concentrations are sub-fractionated using polyethylene glycol precipitation to provide a more meaningful clinical measurement of the bioactive monomeric prolactin content. Manufacturers of prolactin assays should strive to minimise interference from macroprolactin in their assays. Clinical laboratories should introduce screening procedures to exclude macroprolactinaemia in all patients identified as having hyperprolactinaemia. Clinicians should be aware of this potential diagnostic pit fall and insist on PEG screening of all hyperprolactinaemic sera.

Pituitary function in patients with enlarged sella turcica and primary empty sella syndrome

The pituitary function in 20 patients with primary empty sella syndrome has been evaluated. The only endocrine symptom was secondary amenorrhoea in four patients. In half of the patients, pituitary function tests showed minor abnormalities, the most common being impaired growth hormone response to glucagon. In addition to the empty sella, other intracranial abnormalities such as pituitary tumour and hydrocephalus were found in four patients. Although commonly a benign condition, the empty sella may occasionally be associated with clinically important endocrine dysfunction, pituitary tumours and other intracranial abnormalities.

Hyperprolactinemia

In several respects prolactin is unique among anterior pituitary hormones. The primary regulation of prolactin secretion is mediated through hypothalamic inhibition, and the diagnosis of hyperprolactinemia can be established without the use of stimulation or suppression tests. Documenting the presence of hyperprolactinemia is not difficult-the challenge is in identifying the cause of the hormone hypersecretion. With immunoradiometric assays falsely low levels of prolactin are occasionally seen in patients with macroadenomas and very high serum prolactin (the hook effect). Macroprolactin should be suspected when a patient with hyperprolactinemia does not present with typical clinical symptoms, and all hyperprolactinemic sera should be screened for macroprolactin. With prolactinomas, prolactin levels generally parallel tumor size. Prolactin secreting macroadenomas are typically associated with levels that exceed 250 microg/l and may exceed 1,000 microg/l. Large non-functioning adenomas also lead to hyperprolactinemia but levels virtually never exceed 94 microg/l. Acquired and isolated prolactin deficiency is rare.

"Hook effect" in prolactinomas: case report and review of literature

OBJECTIVE

To present a case of the "hook effect" occurring in the prolactin immunoassay in a patient with giant prolactinoma and to review this phenomenon.

METHODS

We describe the clinical, biochemical, radiologic, and pathologic data of a patient with a giant prolactinoma, in which dilution testing of serum prolactin levels confirmed the presence of the hook effect. We discuss the historical and mechanistic aspects of the hook effect and then review its occurrence with the prolactin assay.

RESULTS

A 65-year-old man sought medical attention because of headaches, personality changes, and "bulging" eyes. Cranial magnetic resonance imaging disclosed a 10-cm-diameter, lobulated, heterogeneous, locally invasive mass in the anterior skull base and cranial fossa. Initial laboratory testing showed a prolactin level of 164.5 ng/mL (normal range, 1.6 to 18.8). The pathology specimen from his surgical debulking procedure was consistent with prolactinoma. Retesting of the original serum prolactin sample with serial dilutions revealed a prolactin level of 26,000 ng/mL. A postoperative diluted prolactin level was 22,000 ng/mL. Both prolactin samples demonstrated the hook effect. Dopamine agonist therapy was initiated, and the prolactin level and size of the tumor decreased substantially. The hook effect most commonly occurs when excess antigen (for example, prolactin) is present during testing. Dilution testing can counteract this assay phenomenon.

CONCLUSION

Clinicians should be aware of this laboratory phenomenon when evaluating large pituitary or parasellar masses. When the hook effect is suspected, dilution testing of prolactin samples may prevent incorrect diagnosis and unnecessary surgical intervention in patients with prolactinomas.

Low recurrence rate after partial hypophysectomy for prolactinoma: the predictive value of dynamic prolactin function tests

OBJECTIVE

To determine the factors influencing the outcome of transethmoidal partial hypophysectomy for suspected prolactinoma and the predictive value of pre and post-operative dynamic PRL function tests.

DESIGN

A retrospective study of patients undergoing surgery for a suspected prolactinoma in Cardiff between 1979 and 1989.

PATIENTS

Eighty-two hyperprolactinaemic patients (75 women, seven men) diagnosed as having a prolactinoma on the basis of dynamic PRL function tests, radiological investigation and exclusion of other causes.

MEASUREMENTS

TSH and PRL responses to domperidone (10 mg i.v.) and TRH (200 micrograms i.v.) measured preoperatively, 2 months post-operatively, and annually thereafter. CT scan performed preoperatively in 58 patients. Operative findings, including adenoma size, documented in each case.

RESULTS

Forty-two patients (51%) had microadenomas (less than 10 mm), 37 (46%) had macroadenomas and in three no tumour was found at operation. Preoperatively, normal responses of both TSH (incremental rise less than 2.0 mU/l) and PRL (greater than 100% rise) to domperidone were observed in two patients only: both had an abnormal vascular supply to the pituitary rather than an adenoma. Serum PRL was normalized in the early post-operative period (less than 72 h; 'early cure') in 65 patients (79%). The highest early cure rate (96%, n = 26) was in patients with adenomas of 5-9 mm, lower rates being achieved for lesions of 10-19 mm (80%, n = 30), less than 5 mm (63%, n = 19) or greater than or equal to 20 mm (57%, n = 7). The early cure rate was strongly correlated with preoperative PRL, ranging from 100% in patients with PRL less than 1000 mU/l (n = 13) to zero in those with PRL greater than 10,000 mU/l. Dopamine agonist therapy of between 5 weeks and 4 years duration prior to surgery was associated with a significantly reduced early cure rate (60 vs 94%, P less than 0.02) in macroadenoma but not microadenoma patients. Recurrent hyperprolactinaemia during mean follow-up of 51.7 months occurred in eight patients (12%), in five cases within 2 months of surgery and in the others at 26, 48 and 50 months. Recurrence could not be predicted from any preoperative parameter, but a serum PRL greater than 150 mU/l 1-3 days following microadenomectomy was associated with early recurrence and probably indicates failed surgery. An abnormal response of TSH to domperidone was documented 2 months post-operatively in 11/60 patients with normal basal PRL, and preceded all three late recurrences. Of four patients with abnormal responses of both PRL and TSH at this time, two have relapsed to date.

CONCLUSIONS

In carefully selected patients, partial hypophysectomy is an acceptable alternative to medical treatment for prolactinoma. Preoperatively, dynamic tests accurately identified those patients whose hyperprolactinaemia was non-adenomatous in origin and, post-operatively, identified a subgroup of patients at increased risk of late recurrence.

Multihormonal regulation of the human prolactin gene expression from 5000 bp of its upstream sequence

We have cloned DNA sequences extending up to 6000 bp upstream from the first exon of the human prolactin (hPRL) gene. 5000 bp of these upstream sequences were fused to a CAT reporter gene and shown to provide tissue-specific transient expression in rat pituitary GH3 cells. Multihormonal response was found in this transient expression assay, leading to significant 2- to 5-fold induction by addition of 8-chlorophenylthio-cyclic AMP, thyrotropin-releasing hormone, epidermal growth factor, basic fibroblast growth factor, phorbol myristate acetate, a calcium channel agonist (Bay K-8644) and triiodothyronine. A 3-fold inhibition was observed in the presence of the glucocorticoid agonist dexamethasone. The sequence of the hPRL promoter was determined up to coordinate -3470. Computer similarity search between the rat and human sequences showed two highly conserved regions corresponding to the proximal and distal tissue specific enhancers described in both PRL promoters.

Hyperprolactinemia in multiple sclerosis

In order to clarify endocrine abnormalities due to hypothalamic involvement in multiple sclerosis (MS), serum prolactin levels were measured in 27 patients with MS and 22 healthy subjects. The presence of hypothalamic lesions was also studied by magnetic resonance imaging (MRI). Serum prolactin levels were found to be significantly higher in MS patients than in healthy controls in both sexes. Although only one patient had galactorrhea, one-third of the MS patients had mild to moderate hyperprolactinemia, which was a 4-13-fold increase over the mean value of healthy subjects. The results of thyrotropin-releasing hormone, sulpiride, L-DOPA and bromocriptine loading tests suggested a hypothalamic dysfunction, rather than pituitary prolactinoma in MS patients. Four of eight patients with hyperprolactinema had diencephalic hypothalamic lesion(s) contiguous with the third ventricle on the brain MRI, while none of the normoprolactinemic patients had any lesions in the diencephalon. All relapsing-remitting patients with hyperprolactinemia showed a rise in prolactin levels in the acute stage of the relapse and a decrease during the recovering stage and the following remission phase. Our findings suggest that latent hyperprolactinemia due to hypothalamic dysfunction occurs frequently in MS patients in relapse. The increase of serum prolactin is considered to be a sensitive indicator for hypothalamic lesions in MS.

Long-term follow-up of 'cured' prolactinoma patients after successful adenomectomy

The long-term follow-up (greater than or equal to 4 years) of clinical, hormonal and radiological aspects in 22 'cured' prolactinoma patients after adenomectomy was studied. Dynamic secretion of PRL and TSH was also evaluated, in order to identify the persistence of any underlying abnormality of hypothalamic pituitary control and to predict relapses. A relapse into hyperprolactinaemia was shown in 36% of patients 5-90 months (mean 46) after surgery. This was accompanied by reappearance of clinical symptoms but not by the radiological demonstration of the adenoma in any patients. A significant PRL rise after domperidone, a dopaminergic antagonist drug, was shown in cured patients after surgery (mean +/- SEM peak, 2977 +/- 645 mU/l) but this was markedly lower than that observed in control subjects (5732 +/- 440 mU/l). In fact, normal PRL increments were shown in only 6/16 (37%) patients. TSH hyper-responsiveness to domperidone normalized in only 46% of patients. Similar PRL responses to those obtained with domperidone were shown when a TRH test was given. A relapse into hyperprolactinaemia was observed in six of ten (60%) non-responders to domperidone and in four of seven (57%) non-responders to TRH, whereas six normal responders to domperidone and TRH had not relapsed at that time. Plasma PRL levels during pregnancy showed increments lower than those observed in normal pregnant women only in domperidone and TRH non-responder patients. These results indicate that a relapse into hyperprolactinaemia and a blunted PRL rise during pregnancy were present only in patients with persistently reduced PRL response to dynamic tests.

TRH raises cytosolic Ca2+ in human adenomatous lactotrophs

The effect of TRH on cytosolic free calcium concentrations, [Ca2+]i, was evaluated on cell suspensions obtained from 6 human PRL secreting pituitary adenomas. In these cells resting [Ca2+]i levels were variable (mean +/- SE; 103.8 +/- 6.5, n = 25); the addition of 100 nM TRH caused a marked [Ca2+]i rise within 20 sec., the peak values ranging from 200 to 437 nM (285 +/- 10.8 nM, n = 10). The transients induced by TRH were composed by a rapid increase, due to mobilization of calcium from intracellular stores, followed within a few seconds by a lower plateau which was due to stimulated influx from the extracellular space. In fact, when EGTA and verapamil were applied after TRH they caused the Ca2+ plateau to dissipate rapidly. The addition of 1 microM dopamine (DA) caused a substantial decrease of resting [Ca2+]i (about 10-30%) as well as an inhibition of the plateau phase induced by TRH. The effect of DA completely depended on extracellular Ca2+. The TRH-induced transients observed in adenomatous cells were quite similar in size and time course to those recorded in normal rat lactotrophs. As previously observed in rat lactotrophs, in adenomatous cells treatment with pertussis toxin (PTx, 1 microgram/ml for 4 h) was unable to affect the [Ca2+]i transients induced by TRH while completely abolished the effect of DA. The effects of TRH on in vivo and in vitro PRL secretion were also evaluated. Before surgery, no patient showed a positive response to the iv administration of 200 micrograms TRH (serum PRL levels: 95 +/- 62 ng/ml in basal conditions vs 124 +/- 92 after TRH, P = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of two thyrotrophin-secreting pituitary adenomas: evidence for dopamine receptor deficiency

Of 22 previously reported patients with TSH-secreting pituitary adenomas challenged with dopamine agonists, 18 showed no decrease in serum TSH. There have been few in-vitro studies of these rare tumours so the mechanism of the dopaminergic resistance has remained obscure. We describe two further patients with thyrotrophinomas; the first was thyrotoxic (T3 6.1 nmol/l, TSH 7 mU/l) and the second was diagnosed after radioiodine for presumed Graves' disease. The second patient had an alpha-subunit: TSH molar ratio less than unity (0.27). In-vivo TSH responses to TRH, bromocriptine and domperidone were compared with those of the resected tumour cells in vitro, the latter studied using a continuous perifusion system. Dopamine receptors were sought in membranes from each tumour using a radioreceptor assay employing 3H-spiperone. Patient 1 showed significant increases in serum TSH (7 to 13 mU/l) and alpha-subunit (18.7 to 385 ng/ml) after 200 micrograms TRH (i.v.) but patient 2 showed no such increases (TSH: 69 to 72 mU/l, alpha-subunit: 4.9 to 5.2 ng/ml). Neither patient showed a change in serum TSH following bromocriptine 2.5 mg (orally) or domperidone 10 mg (i.v.), though serum PRL responded normally. Serum TSH from patient 1 was of apparently normal molecular size but increased bioactivity (B/I ratio 3.8) and that from patient 2 was of increased molecular size but reduced bioactivity (B/I ratio 0.1). Tumour cells from each patient immunostained for TSH beta and alpha-subunit, and secreted TSH in vitro. The first showed dose-dependent TSH release after TRH (1-100 ng/ml) which could not be inhibited by dopamine (5 mumol/l) but the second was unresponsive to TRH in vitro. Neither tumour showed inhibition of TSH release by dopamine (5 mumol/l) or bromocriptine (0.01-10 nmol/l) and neither contained membrane-bound dopamine receptors. The results suggest that the dopaminergic resistance typical of most TSH-secreting pituitary adenomas may be due to altered or absent membrane-bound dopamine receptors.

Perifusion studies of bromocriptine-treated and untreated macroprolactinomas: effects of dopamine, bromocriptine and TRH

There have been no detailed in-vitro studies of PRL secretion by human macroprolactinoma cells exposed to bromocriptine (BC) to within a few days of surgical removal. We have studied cells from four such tumours (serum PRL 7.05-247 U/l) and six untreated tumours (serum PRL 4-80.35 U/l) using a perifusion technique. The BC-treated tumours had shown tumour shrinkage and were treated until 40-96 h before surgery, but in one patient serum PRL had not suppressed below 15 U/l despite chronic treatment. Pretreatment serum PRL responses to TRH were blunted in all 10 patients. During perifusion with dopamine (DA, 5 mumol/l) untreated prolactinomas had a higher PRL secretion rate (19.3 +/- 2.7 microU/mg tissue/min, mean +/- SEM) than BC-treated (3.9 +/- 0.7, P = 0.005). When DA was removed, PRL secretion from untreated tumours increased to 129.7 +/- 18.7 microU/mg/min, but in three of the BC-treated, little increase occurred. In the fourth (from the patient whose serum PRL had not fully suppressed) PRL secretion increased from 4.4 to 25.6 microU/mg/min after DA withdrawal, and DA and BC dose-related inhibition of PRL was similar to that observed in untreated tumours. TRH (10 ng/ml), without DA, provoked increased PRL release from both untreated (266% basal secretion, n = 3) and BC-treated (298%, n = 3) tumours; this effect was completely inhibited by DA (5 mumol/l). The absence of hormones other than PRL following potassium (55 mmol/l) excluded contaminating normal pituitary. We conclude: (1) The effects of BC on prolactinoma PRL secretion may persist for at least 4 days; (2) partial in-vivo BC resistance can be due to factors other than DA receptor malfunction; (3) the apparent discrepancy between in-vivo and in-vitro TRH responses was consistent with the presence of increased hypothalamic DA tone in vivo; and (4) BC may have differential effects on TRH and DA-controlled PRL pools in the tumourous lactotroph.

Abnormal responses to vasoactive intestinal peptide and corticotropin releasing hormone during the spontaneous remission of Cushing's disease

Abnormalities in hypothalamic-pituitary adrenal axis function were demonstrated by measuring plasma adrenocorticotropin abnormal concentrations following Vasoactive Intestinal Peptide (VIP) and Corticotropin Releasing Hormone (CRH) administration during a phase of remission of Cushing's disease in a 45-year-old female patient. When observed 80 days after the first examination, the patient no longer showed cushingoid features and serum cortisol and plasma ACTH were not abnormally high. VIP infusion (75 micrograms during 12 min) induced a significant increase in serum cortisol and ACTH plasma levels with respect to the normal unresponsiveness. Exaggerated plasma ACTH response to CRH (50 micrograms iv) was also observed. We conclude that the study of ACTH and cortisol response to VIP and CRH may be useful in revealing Cushing's disease even during a remission phase of the disorder.

The circadian rhythms of thyrotrophin and prolactin secretion

As with other anterior pituitary hormones, the secretion of both thyrotrophin (TSH) and prolactin (PRL) displays a circadian variation with different patterns for each hormone. In recent years there has been a substantial increase in the understanding of the neuroregulation of TSH and PRL. However the primary events involved in the generation of their circadian rhythms remains unclear. Regulatory pathways comprise two major groups: central factors, where the control is exerted by the central nervous system via the hypothalamus and peripheral factors, which include all extra CNS mechanisms. The first group is represented mainly by neuropeptides and neurotransmitters controlling TSH and PRL release, whereas the second one comprises both physical phenomena such as variations in plasma volume or postural changes and hormonal influences arising from target glands such as the adrenal, the thyroid and the gonads.

The natural history of untreated microprolactinomas

The development of radioimmunoassay (RIA) for prolactin (PRL) and sensitive high-resolution computed tomography (HRCT) has resulted in documentation of large numbers of microprolactinomas (microPRL). To try to define the rate and prevalence of tumor growth, the authors performed serial HRCT scans in 38 untreated patients, an average of 31.7 months apart. In no patient, including two patients with exuberant rises in PRL, was there any evidence of subtle tumor growth. The authors conclude that the majority of patients with microPRL have a benign course, with tumor growth occurring, if at all, over a period of years.

Assays for prolactin: guidelines for the provision of a clinical biochemistry service

This paper summarises the views of the authors on the provision of a prolactin assay service. We discuss the pathophysiology of prolactin secretion and the clinical indications that arise from that. We cover the rather complex issue of the definition of normal and elevated prolactin levels. From these considerations, certain guidelines on the analytical performance of prolactin assays and their provision in a clinical biochemistry service are given. The extent to which currently available methods and performance as revealed by the UK External Quality Assessment Scheme (EQAS) match these guidelines are described and certain conclusions are reached. Finally, probable future developments are briefly discussed. The main conclusions and recommendations are as follows: Reagents of appropriate quality are available to enable prolactin immunoassays to be provided in UK clinical biochemistry laboratories. These are provided either separately or in the form of kits from both commercial and NHS sources. There is no requirement for individual laboratories to undertake their own antiserum production or prolactin iodination. Acceptable performance (as defined using internal QC procedures and the UK EQAS) is achievable using these reagents/kits, although one commercial kit shows a consistent marked negative bias. Reference ranges, including 'normal ranges', show considerable between-centre variability. Many centres have not established their own ranges, even those using in-house methods. Reference ranges for use in clinical biochemistry laboratories are proposed in this report. Some general guidance on the provision of a prolactin service is given, although this does not differ in principle from that appropriate for other peptide hormone analytes. There is no evidence that centres with small workloads perform any worse than average, although it may be more cost-efficient for such centres to send the samples elsewhere. As with other peptide analytes, non-isotopic immunometric methodology is likely to replace current radioimmunoassay methods in the near future.

High-resolution computed tomography in pituitary microadenoma: is seeing believing?

Controversy surrounds the reliability of high-resolution computed tomography (CT) in the identification of functioning microadenomas, especially in patients with hyperprolactinaemia and hypercortisolaemia. We studied 34 such patients: each underwent a high-resolution CT examination of the pituitary gland and each had a trans-sphenoidal exploration. Computed tomography showed 28 focal abnormalities but only 20 of these were confirmed to be due to a tumour at operation. In the other eight the tissue at the site of the radiological abnormality was normal histologically. In a total of 29 patients a tumour was found at operation and confirmed histologically; 20 were at the site of an abnormality shown by CT but in nine a tumour was found in a part of the gland judged to be normal radiologically. In general, good correlation between CT and the surgical findings was found only with tumours more than 6 mm in size. Of the indirect signs of a tumour, such as stalk deviation and a convex upper surface of the gland, only the former showed any correlation with the presence of a tumour. The results show that cautious, even sceptical interpretation of pituitary CT scans is essential and suggest that this investigation is not sufficiently reliable to be used as a routine in the assessment of hyperprolactinaemia or Cushing's syndrome. Computed tomography should be reserved for patients undergoing pituitary surgery, those with an enlarged fossa on plain radiography and those with extreme hormone hypersecretion.

The preoperative and postoperative investigation of TSH and prolactin release in the management of patients with hyperprolactinaemia due to prolactinomas and nonfunctional pituitary tumours: relationship to adenoma size at surgery

We report here our results of the pre- and post-operative assessment of prolactin and TSH status in 41 hyperprolactinaemic patients who underwent pituitary surgery over a 5 year period. Preoperatively in patients with prolactinomas (n = 33) the TSH response to domperidone decreased with increasing adenoma size. When the data are expressed on a group mean basis the exaggerated TSH response to domperidone in preoperative prolactinoma patients was reduced significantly in patients rendered normoprolactinaemic by surgery but persisted in those who remained hyperprolactinaemic. Similarly the reduced preoperative PRL responses to domperidone and TRH were significantly increased by successful surgery. In contrast patients with stalk-compression hyperprolactinaemia (n = 6) due to larger lesions which were not prolactinomas all showed reduced or absent TSH responses to domperidone. The PRL responses to domperidone and TRH were reduced or absent both in patients with prolactinomas and in those with stalk-compression hyperprolactinaemia. All patients with stalk-compression hyperprolactinaemia showed a delayed pattern of TSH response to TRH with 60 min values being greater than 20 min ones. In contrast a normal pattern of TSH response to TRH was observed in all patients with hyperprolactinaemia due to prolactinomas. Postoperatively TSH and PRL responses were largely unchanged in patients with stalk-compression hyperprolactinaemia regardless of whether normoprolactinaemia was restored by surgery. In conclusion a reduced or absent PRL response to TRH or domperidone is not diagnostic of the presence of a prolactinoma since it occurs in hyperprolactinaemic patients with prolactinomas or stalk-compression. In contrast, the TSH response to acute dopamine antagonism is exaggerated in most patients with small prolactinomas but not in those with stalk-compression hyperprolactinaemia and we have found this to be helpful diagnostically since the presence of an exaggerated TSH response to dopamine antagonism is evidence against the presence of stalk-compression hyperprolactinaemia. The observation of a delayed TSH response to TRH in a hyperprolactinaemic patient should alert the clinician to the possibility of stalk-compression hyperprolactinaemia due to a large lesion which may not be a prolactinoma.

Use of DES-treated rats as an animal model for assessment of pituitary adenoma imaging agents

Prolactin (PRL) secreting pituitary adenomas are the most common type of pituitary tumors. An imaging agent which specifically localized in prolactinomas would be of considerable clinical value for both initial detection and also for monitoring the effects of dopamine agonist therapy. Tritiated spiroperidol (3HSp) was selected for initial evaluation as a possible imaging agent based on: demonstrated localization in the pituitary and demonstrated binding to human PRL-secreting tumor tissue. DES was implanted in Fischer F344 rats and induced prolactinoma formation was evidenced by increased pituitary weight, elevated serum PRL levels and by an increase in the proportion of PRL-secreting cells in the pituitary. 3HSp concentrations in pituitary and other tissues of DES-treated rats were assessed in female rats and correlation studies showed that a 5-fold increase in serum PRL was associated with a 6-fold increase in both pituitary weight and % dose/organ accumulation of 3HSp. The number of pituitary D2 receptors per mg of protein in tissue homogenates was similar in both normal and DES-treated females. A blocking study with (+)-butaclamol demonstrated a D2 receptor-mediated component to 3HSp localization. In summary, an animal model for prolactinoma was characterized. An assessment of 3HSp accumulation indicates that radiolabelled spiroperidol shows excellent potential for detecting PRL-secreting tumors of the pituitary.

Management of selected patients with hyperprolactinaemia by partial hypophysectomy

Results are reported in 35 patients with prolactinomas who underwent pituitary surgery within the past five years. After surgery prolactin concentrations became normal in 26 patients and symptoms were alleviated, and nine normal pregnancies were achieved in seven women, including all those who had complained of infertility. Normal prolactin concentrations were restored in 16 of 17 patients with tumours 5-19 mm in diameter but in only six of 11 with tumours less than or equal to 4 mm and four of seven with tumours greater than or equal to 20 mm. Normal prolactin concentrations were restored in all those with preoperative concentrations below 1000 mU/l but in none of those with concentrations above 10 000 mU/l. Although not all of the patients were followed up for five years, hyperprolactinaemia did not recur in any patient whose prolactin concentration had returned to normal six weeks after surgery. This included 16 patients with macroprolactinomas (greater than 10 mm in diameter), who were followed up for from two to five years. These data contrast strikingly with those reported by others at similar stages of follow up and show clearly that partial hypophysectomy offers an acceptable alternative treatment for selected patients with prolactinomas.

Treatment of presumed prolactinoma by transsphenoidal operation: early and late results

Seventy seven patients who were presumed to have a prolactinoma on the basis of biochemical findings underwent transsphenoidal operation between October 1977 and September 1983. Sixty one patients were found to have a microadenoma, and hyperprolactinaemia was cured in 46 of these, amenorrhoea in 39 (80% of those with the symptom), galactorrhoea in 32 (80%), and infertility in 31 (82%). Four of eight patients found to have a macroadenoma were also satisfactorily treated with surgery. Two patients had a lesion other than a prolactinoma, and in six a tumour could not be found at operation; four of these last eight patients had a normal serum prolactin concentration after operation. Recurrent hyperprolactinaemia was rare, occurring in only three patients in the series overall; among the 32 patients followed up for more than five years only two of the 22 whose operation had initially been successful developed recurrent hyperprolactinaemia.

The influence of oestrogens on the sensitivity of PRL, TSH and LH to the inhibitory actions of dopamine in hyperprolactinaemic patients

The effects of oestrogen priming on the response of serum PRL, LH and TSH to dopamine (DA) infusion have been studied in hyperprolactinaemia. Seven hyperprolactinaemic females (aged 22-57 years; basal PRL 911-5130 mU/l, normal less than 420 mU/l), had submaximal DA infusions (0.06 micrograms/kg/min) over 3 h. The DA was repeated at the same dose after pretreatment with ethinyl oestradiol (E2) 100 micrograms daily by mouth for 3 d, and after a further 2 week interval, following pretreatment with tamoxifen (TAM) 20 mg twice a day by mouth for 3 d. Ethinyl oestradiol pretreatment stimulated a rise in basal PRL levels in all subjects (mean +/- SE, mU/l; 2903 +/- 761 vs 2293 +/- 684, P less than 0.05) while TAM produced a higher but more variable increase in basal PRL levels (mean +/- SE, mU/l; 3402 +/- 757, P = n.s.). The individual increments in basal PRL levels after both E2 and TAM pretreatment showed a significant positive correlation with the greater decrement in PRL levels during E2 and TAM primed DA infusions (E2, r = 0.93, P less than 0.01, TAM, r = 0.83, P less than 0.05). E2 pretreatment produced a rise in basal LH levels in 5/7 patients, and there was a significant positive correlation between the rise in basal LH levels after E2 and the decremental change in LH levels in E2 primed DA infusions (r = 0.94, P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

The interaction of trh and dopaminergic mechanisms in the regulation of stimulated prolactin release in man

The manner by which dopaminergic and TRH mechanisms interact to control PRL release is not known. Whilst dopamine receptor antagonists and TRH both release PRL, it is not known if the PRL released by these two mechanisms reflects similar aspects of physiological control, or if PRL responses to these mechanisms of release can be dissociated. We addressed this question by studying the PRL responses to maximal stimulatory dose of TRH and domperidone (a DA receptor antagonist), which were administered sequentially, simultaneously or separately on different occasions. Six normal volunteers undertook three sets of studies: (1) standard PRL stimulation tests to 400 micrograms TRH, 5 mg domperidone or simultaneous TRH/domperidone administration, (2) domperidone bolus-infusion study in which either 5 mg domperidone or 400 micrograms TRH was administered i.v. at 120 min during a 240 min infusion of domperidone (50 micrograms/min) which was preceded by a 5 mg i.v. bolus of the drug, and (3) TRH bolus-infusion study in which domperidone or TRH was administered i.v. at 120 min during a 240 min infusion of TRH (0.4 micrograms/min) which was preceded by a 400 micrograms i.v. bolus of the drug. In Study 1, simultaneous TRH/domperidone administration induced an incremental rise in PRL (5195 +/- 940 mIU/l) which was significantly greater (P less than 0.0005) than with either domperidone (3730 +/- 825 mIU/l) or TRH (1335 +/- 300 mIU/l) alone. In study 2, TRH administration at 120 min resulted in a significant rise (P less than 0.01) in PRL (delta PRL 960 +/- 232 mIU/l) whilst the second dose of domperidone did not, thus suggesting that the initial bolus and subsequent infusion had resulted in complete DA receptor blockade. In Study 3, domperidone administered at 120 min induced a marked rise in PRL (delta PRL 3609 +/- 963 mIU/l). In contrast, the corresponding TRH stimulus resulted in a small rise (delta PRL 142 +/- 32 mIU/l) suggesting that the PRL release induced by the initial bolus and subsequent infusion had been near maximal. Thus, TRH is able to induce significant PRL release in the presence of maximal DA receptor blockade, and domperidone, in the presence of maximal TRH stimulation, is also capable of inducing significant PRL release. These observations together with the ability of TRH/domperidone to induce a greater PRL response than either agent alone, suggest that each stimulus has a specific releasing action on a fraction of intracellular PRL which is not accessible to the other.(ABSTRACT TRUNCATED AT 400 WORDS)

Hyperprolactinaemia, amenorrhoea and galactorrhoea due to a pituitary thyrotroph adenoma

A case of hyperprolactinaemia/amenorrhoea-galactorrhoea syndrome is described. A prolactinoma was diagnosed, but histology of the excised tumour revealed it to be a thyrotoph adenoma. alpha-subunit and beta-TSH levels were lowered after the operation. The significance of this tumour is discussed.

Long-term bromocriptine therapy may restore the inhibitory control of prolactin release in some patients with pathological hyperprolactinemia

While bromocriptine is effective in controlling hyperprolactinemia, it is not known if bromocriptine therapy can restore the abnormal regulation of prolactin (PRL) release found in patients with pathological hyperprolactinemia. We report 15 hyperprolactinemic patients treated for a mean duration of 5.5 +/- 0.6 years (mean +/- SE) in whom stimulation tests to assess PRL control mechanisms [thyrotropin releasing hormone (TRH) and metoclopramide] were performed before and at least one month after withdrawal of bromocriptine therapy. The basal PRL level after withdrawal of bromocriptine therapy was significantly lower (p less than 0.001) than that before therapy. All patients had blunted PRL stimulatory responses to TRH and metoclopramide (% delta 16.0 +/- 5.6%) before treatment. After withdrawal of bromocriptine, PRL responses to stimulatory tests were significantly improved in seven patients (termed 'responders', % delta 376 +/- 55%) but remained unchanged in eight patients (termed 'non-responders', % delta 9.2 +/- 3.0%). Basal PRL levels were significantly lower (p less than 0.01) in responders (290 +/- 35 mIU/l) than in non-responders (10360 +/- 6790 mIU/l). Four of the responders have maintained normoprolactinemia and normal stimulated PRL responses for 15 months to three years following cessation of bromocriptine therapy and appear to be in remission. Favourable factors amongst the responders were the female sex, absence of a macroadenoma, and a pre-treatment PRL level below 3000 mlU/l. PRL stimulation tests performed before therapy could not predict which patients would respond. No relationship was found between duration of therapy, or age at presentation, and improvement after bromocriptine.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential effects of acute DA receptor blockade with domperidone on LH and TSH release in patients with hyperprolactinemia

Since dopamine (DA) has been implicated in the inhibitory control of both TSH and LH, we have compared TSH and LH levels following dopamine (DA) receptor blockade with domperidone in patients with hyperprolactinemia due to presumed prolactinomas. Eight euthyroid patients (aged 19-37 yr) with presumed prolactinomas each received domperidone (10 mg iv) at 11:00 and 23:00 h and tests were separated by at least one week. Basal TSH levels were significantly greater at 23:00 than at 11:00 h (2.7 +/- 0.5 vs 1.7 +/- 0.4 mU/l, mean +/- SE, p less than 0.01) whereas basal LH levels did not differ. All subjects showed clear rises in basal TSH levels following drug administration and these were significantly greater at 23:00 than at 11:00 h (p less than 0.02 at each time point). In contrast there was no alteration in LH levels following drug administration at either time of day. These data suggest that the mechanisms underlying the dopaminergic control of TSH and LH are different in these patients. Furthermore the data argue against an anterior pituitary or median eminence site of action of DA in the inhibition of LH release in hyperprolactinemia since domperidone does not penetrate the blood brain barrier to any appreciable extent.

The inability of dynamic tests of prolactin and TSH secretion to differentiate between tumorous and non-tumorous hyperprolactinemia

Certain hyperprolactinemic patients have an obvious pituitary tumor while others with normal pituitary radiology may or may not harbor a pituitary microadenoma. A variety of biochemical tests have been proposed to distinguish between those with and those without pituitary tumors. The aims of this study were: firstly to examine these tests to assess their efficacy in differentiating between patients with radiologically-demonstrated pituitary tumors and normal controls; and secondly to establish if those hyperprolactinemic patients with normal radiology formed two distinct groups biochemically as might be expected if some did and some did not have tumors. The prolactin (PRL) and thyroid stimulating hormone (TSH) response to domperidone and the PRL response to TRH and insulin-induced hypoglycemia have thus been examined in hyperprolactinemic subjects with and without radiological evidence of an adenoma and in normal controls. The basal serum PRL was similar in patients with and without radiological evidence of a pituitary adenoma. The serum PRL response to all stimuli studied, expressed as a percentage of initial values, was blunted in patients with known pituitary tumors with total separation from values in control subjects. Results for patients with normal pituitary radiology were similar to those for patients with tumors with minimal overlap with controls. The peak TSH increment after domperidone was exaggerated in patients with known tumors, but overlap with control values was observed in 25%. In patients with normal radiology the peak TSH increment after domperidone was similarly increased but again overlap with control values occurred in 28%. Cluster analysis showed no evidence of two subgroups of response with in the hyperprolactinemic patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Multiple intracranial metastases from a prolactin secreting pituitary tumour

A 28 year old man presented with partial hypopituitarism and signs of a pituitary tumour. A chromophobe adenoma was partially removed by right frontal craniotomy. Seven years later complete hypopituitarism and hyperprolactinaemia were documented, at which time there was no evidence of tumour recurrence of CT scan. The patient was treated with bromocriptine but the pituitary tumour redeveloped a year later. Nine years after the original operation the first metastasis was demonstrated together with very high prolactin levels. The intracranial metastasis, and the pituitary tumour were removed at a second craniotomy following which the prolactin concentration fell. Further metastases developed subsequently and the patient died 12 years after the initial diagnosis. At autopsy multiple metastases were found in the brain, tumour cells were present in the subarachnoid space and in cerebral veins. The pituitary tumour and secondaries were shown by immunocytochemistry to contain prolactin but not ACTH or growth hormone. This appears to be the third well documented case of a metastasizing, prolactin secreting pituitary tumour.

Prolactin response to thyrotropin-releasing hormone (TRH) in patients with hypothalamic-pituitary disease

The prolactin (PRL) response to thyrotropin-releasing hormone (TRH) was evaluated in 686 patients over a 4-year period. Of the 170 control subjects tested, none had a blunted PRL response to TRH. Eighty patients with prolactinomas documented by surgery were tested. Ninety-five percent (76 of 80) of these patients had an abnormally blunted PRL response to TRH. Of the 87 patients with a prolactinoma who did not undergo surgery, 98% (85 of 87) had a blunted PRL response to TRH. Many patients with other pituitary and hypothalamic diseases (pituitary tumors other than prolactinomas [Cushing's disease, acromegaly, chromophobe adenoma], craniopharyngioma) also had an abnormal PRL response to TRH (79 of 153, 52%). In the majority of patients with hyperprolactinemia due to dopamine antagonist medications, TRH stimulation did not produce a normal rise in PRL. The TRH test may be helpful in confirming the diagnosis of prolactinoma, but it is not a decisive factor in the diagnosis or management of this entity.

Twenty-four-hour prolactin secretory patterns in women with galactorrhea, normal menses, normal random prolacting levels and abnormal sellar tomograms

During a systematic study of women with idiopathic galactorrhea, we observed several patients with normal random serum prolactin (PRL) levels and normal menses, but abnormal sellar tomograms characteristic of a pituitary adenoma. To test the hypothesis that these women might have intermittent PRL hypersecretion, we studied PRL secretion by sampling blood every half hour for 24 h in 10 patients and for 17.5 h in another, and compared the findings to those of a group of 5 normal women. The mean 24-h PRL of the 10 patients (16.8 +/- 7.8 ng/ml; mean +/- SD) was not significantly different from that of the normal women (13.6 +/- 3.2 ng/ml), and each patient showed a normal sleep-associated PRL increment. Three individuals exhibited an abnormally elevated 24-h PRL (greater than 20 ng/ml). Increased PRL secretion occurred primarily at night or in the afternoon. Thyrotropin releasing hormone (TRH) administration caused normal or exaggerated PRL responses in all patients tested. High resolution CT scanning of two of the hypersecretors suggested a microadenoma in one case. In another case whose PRL was normal over 17.5 h, transsphenoidal surgery, carried out because of the tomographic findings and the symptom of headaches, demonstrated a 5-mm chromophobe adenoma that did not contain PRL by immunohistochemistry. Postoperatively the galactorrhea persisted. We conclude that most women with galactorrhea, normal PRL, normal menses, and abnormal tomograms have normal PRL secretion. However, a minority of patients with this syndrome do demonstrate intermittent PRL hypersecretion. The etiology of intermittent PRL hypersecretion and its relevance to galactorrhea have not been determined.(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanisms involved in the prolactin-releasing effect of benserazide

The mechanism(s) underlying the prolactin (PRL)-releasing effect of benserazide (Bz), a peripheral inhibitor of L-aromatic amino-acid decarboxylase, was investigated in the rat. In intact male and female rats, Bz was ineffective to increase significantly plasma PRL at 0.8 mg/kg i.p. but elicited an already maximal effect at 1.6 mg/kg. Bz added to in vitro incubated anterior pituitaries (APs) did not alter PRL secretion at the dose of 3.8 X 10(-6)M but increased PRL release at 10(-4)M. Bz, even at very high doses (up to 10(-3) M), did not displace [3H]spiroperidol binding from AP membrane preparations. In rats having had mechanical ablation of the medio basal hypothalamus (MBH), Bz (15 mg/kg i.p.) induced no rise in plasma PRL and did not counteract the striking inhibitory effect of a dopamine (DA) infusion (5 micrograms/kg per min per 120 min). Administration of Bz (15 mg/kg i.p.) into intact male rats decreased significantly the DA concentrations in the median eminence (ME) but not in the residual hypothalamus and the AP. In the same rats 1-dopa (50 mg/kg i.p.) increased significantly the DA concentrations not only in the ME but also in the hypothalamus and the AP. Bz given concurrently with 1-dopa markedly reduced the rise in DA concentrations induced by 1-dopa in the ME, and greatly potentiated the increase in DA concentrations in the hypothalamus. These data indicate that the mechanism whereby a single administration of Bz increases PRL secretion in the rat is not consistent with the postulated DA receptor antagonist action of the drug, but instead implies inhibition of the decarboxylation of 1-dopa at dopaminergic nerve terminals of the ME.

Nomifensine, TRH and insulin-induced hypoglycemia tests in the diagnosis of prolactinomas

Nomifensine, TRH and insulin-induced hypoglycemia tests were carried out in 37 cases of hyperprolactinemia: 25 were due to PRL-secreting pituitary tumors, 6 cases to GH and PRL-secreting pituitary tumors and 6 to pituitary and suprasellar non secreting tumors. Nomifensine failed to suppress the serum PRL in all subjects and PRL responses to TRH and insulin-induced hypoglycemia were impaired in all patients, irrespective of the origin of hyperprolactinemia. The uniform pattern of PRL response to the above tests in patients with hyperprolactinemia of variable etiology suggests that none of them is specific for prolactinomas.

The interrelationships between prolactin and thyrotrophin secretion following dopaminergic blockage in patients with mild hyperprolactinaemia without any demonstrable pituitary tumour

PRL, TSH and gonadotrophin responses to the dopaminergic antagonist, metoclopramide, were studied in mildly hyperprolactinaemic patients with normal sella radiology and CT scan. Eleven female patients with basal PRL levels ranging from 23 to 124 ng/ml were challenged with intravenous metoclopramide (10 mg) and on subsequent occasions with TRH (200 micrograms) and LHRH (100 micrograms). On the basis of the PRL secretory pattern following metoclopramide and TRH stimulation, the patients were divided into two groups. Group I comprised six subjects who were PRL non-responsive to TRH and metoclopramide. Group II (five subjects) demonstrated PRL responses to TRH and metoclopramide indistinguishable from female controls. Mean +/- SD basal PRL levels were 68.5 +/- 29.9 ng/ml in Group I and not different in Group II (40.6 +/- 12.0 ng/ml). Basal LH levels were increased in Group II, whereas FSH was increased in Group I. Basal TSH levels were lower in Group I than the controls. Following metoclopramide, Group I patients had an increase in TSH from a basal of 2.4 +/- 0.7 microU/ml to a peak of 5.9 +/- 2.7 microU/ml (P less than 0.005) which occurred at 30 min. TSH values were increased above basal at all time intervals following metoclopramide. In contrast, TSH levels did not change in Group II patients or the controls after metoclopramide administration. Both patient groups had TSH responses to TRH similar to the controls. Following LHRH, the LH increase was greater in Group II and the FSH in Group I. In neither group nor the controls did gonadotrophin levels change after metoclopramide. In Group II females, PRL responsiveness to metoclopramide was associated with TSH non-responsiveness. In Group I females, PRL levels failed to rise, whereas TSH increased. The PRL and TSH profile in Group I females is typical of a prolactinoma. It is concluded that PRL as well as TSH determinations following metoclopramide are useful indices in the assessment of hyperprolactinaemia and may be of value in differentiating the functional state from that of a pituitary tumour.

Studies of anterior pituitary-grafted rats: I. Abnormal prolactin response to thyrotropin releasing hormone, clonidine, insulin, and fasting

Although the rat implanted with extra anterior pituitary glands (AP) under the kidney capsule has been widely used as a model of chronic hyperprolactinemia, its hormonal status has not been fully characterized. Using conscious, unrestrained female pituitary-grafted rats and sham-operated littermates, we investigated prolactin (PRL) secretion in response to the following stimuli: thyrotropin releasing hormone (TRH), clonidine, insulin, and fasting. The AP-implanted rats had a greater and more sustained rise in serum PRL after TRH than control rats, reflecting a direct effect of TRH on the ectopic lactotropes. In contrast after clonidine, which acts via the hypothalamus, the serum PRL rose to much higher levels in sham-operated rats than in rats bearing ectopic pituitary tissue. Both insulin-induced hypoglycemia and fasting decreased serum PRL in control rats, but the AP-implanted animals manifested a rise in serum PRL in response to these stimuli. Thus, the AP-implanted rat is not only a valid model of excess and abnormal PRL secretion, but it may also be useful for distinguishing between stimuli requiring an intact hypothalamic-pituitary unit and agents which act directly on the pituitary gland.

Reciprocal pattern of the TSH and PRL responses to dopamine receptor blockade in women with physiological or pathological hyperprolactinaemia

The TSH and PRL responses to administration of the two dopamine (DA) receptor antagonists sulpiride and domperidone, were studied in fifteen normoprolactinaemic subjects, twenty-two post-partum women and sixteen subjects with presumptive evidence of (six subjects) or surgically confirmed (ten subjects) prolactinomas. Sulpiride (100 mg i.m.) or domperidone (10 mg i.v.) elicited a slight increase in basal TSH levels in both normoprolactinaemic and post-partum women, but induced a clear-cut TSH rise in subjects with a tumour. Conversely, sulpiride and domperidone strikingly stimulated PRL secretion in normoprolactinaemic and post-partum women, but only slightly enhanced base-line PRL levels in women with prolactinomas. The reason for the reciprocal pattern of TSH and PRL responsiveness to DA receptor blockade of post-partum women and subjects with prolactinomas is presently obscure. Since baseline PRL levels in the two hyperprolactinaemic states overlapped widely, it would appear that hyperprolactinaemia per se is not responsible for such behaviour.

Psychiatric and social aspects of premenstrual complaint

A number of fundamental methodological problems exist in the area of premenstrual symptomatology and psychiatric ill-health. In the study described these have all been taken into account. The study has been so designed as to make expressly clear the definition of premenstrual complaint being employed and material gathered by means of a retrospective questionnaire is checked by means of an interview administered to a sub-sample and the use of a menstrual diary (Sampson & Jenner, 1977; Dalton, 1978). The use of an interview also permits a careful check to be made of the accuracy displayed by women asked to estimate their particular position in the menstrual cycle at the time of completion of the questionnaire. The use of the premenstrual interview, together with a standardized, semi-structured psychiatric interview specifically designed for the population under study, and a standardized, semi-structured social maladjustment schedule, permits a detailed assessment of the inter-relationship between premenstrual, psychiatric and social variables. Finally, the use of a general practice sample of women attending their general practitioners for many and varied reasons, together with a sample of women drawn from attenders at a specialized premenstrual tension treatment clinic, permits a comparison to be made between the symptom profiles of women in a general practice population who have not overtly identified themselves to the treatment agencies as premenstrual sufferers with a group of women who have so identified themselves. In this way, a more accurate estimate of the numbers of women in general practice samples who manifest a degree of premenstrual complaint equivalent to that shown by special treatment clinic attenders can be achieved.

Effects of oral and intravenous TRH and metoclopramide on PRL and TSH secretion in women

Pituitary secretion of PRL and TSH is under the control of inhibitory dopaminergic and stimulatory TRH-mediated mechanisms. To evaluate the relationships between these regulatory systems, ten healthy women were treated with oral TRH (20 mg twice daily), a dopamine blocking drug, metoclopramide (MC) (10 mg t.d.s.) or placebo for 1 week (from 8th to 14th cycle day). Serum concentrations of PRL, TSH, T3 and T4 were determined before, at the end, and 3 days after the treatments. In addition, PRL and TSH responses to i.v. TRH (200 micrograms) or MC (10 mg) were studied at the end of the oral treatments. Oral TRH treatment was accompanied by increases in basal T3 and T4 concentrations, no change in PRL, and a decrease in TSH 3 days after the end of treatment. Oral TRH did not modify the PRL response to i.v. MC while it eliminated the TSH response to i.v. MC, possibly because of elevated concentrations of thyroid hormones. Oral MC treatment raised the concentrations of PRL, T3 and T4, and also potentiated the PRL response to i.v. TRH, whereas the TSH response remained unaltered. These results demonstrate that dopaminergic and TRH-mediated mechanisms are related in the control of PRL and TSH secretions, perhaps directly or through thyroid hormones.

Use of cavernous sinography to detect aneurysms of anomalies of the infraclinoid carotid artery

✓ Four cases are described to illustrate the ability of cavernous sinography to detect coincidental aneurysms or anomalies of the infraclinoid carotid artery. Sinography may be used as a preliminary step before a transsphenoidal operation, in order to identify the small proportion of cases in which arteriography should be performed.