The thyrotrophin-releasing hormone test in diseases of the pituitary and hypothalamus

The Management of Prolactin-Secreting Pituitary Adenomas

Advances in the investigation and treatment of pituitary tumours over the past decade have necessitated a major reappraisal of the management of these lesions. The recognition that prolactin-secreting pituitary adenomas (prolactinomas) not only represent a further sub-group of secretory tumours but may in fact be the commonest type of pituitary tumour has come at an appropriate time. Refinements in neuroradiological techniques and transphenoidal surgery and the introduction of the dopamine-agonist bromocriptine now offer prospects for early detection and effective treatment, either by selective adenomectomy or by non-invasive therapy with bromocriptine. In a study of 67 patients with large prolactin-secreting pituitary adenomas, 33 have undergone computerised tomography and metrizamide cisternography for assessment of tumour size. In ten of these patients repeat scans following bromocriptine therapy have shown reduction in prolactinoma size in eight. The two patients with no change in tumour size differed from the rest, having received a lower dose of bromocriptine and had prolactinomas as part of the multiple endocrine adenomatosis syndrome (Type I).

Assessment of thyroid function in chronic alcoholics

The clinical manifestations in chronic alcoholics may sometimes mimic those of hyperthyroidism. However, diagnostic aids are somewhat contradictory in many cases. Ten chronic alcoholics with symptoms from the sympathoadrenal system were investigated. A significant increase (p less than 0.01) of T3 at 120 min after TRH stimulation was found despite a blunted TSH response (increment less than 3 mU/l) in some cases. This increase in T3 indicates a preserved thyroid function in chronic alcoholics despite generally low basal T3 levels. It is concluded that T3 determinations at 120 min in connection with TRH test may be an essential parameter in evaluating euthyroid function in chronic alcoholics.

Persistent hypothalamic-pituitary insufficiency following acute meningoencephalitis. A report of two cases

This report concerns two patients, a 43-year-old woman and a 53-year-old man, who developed clinical as well as laboratory signs of permanent gonodal and thyroid failure following an acute intracranial infection--in the woman a meningoencephalitis of unknown origin, and in the man an encephalitis caused by Coxsackie B5. Endocrine investigations were compatible with hypothalamic-pituitary dysfunction, with some of the results favoring a hypothalamic lesion. Perhaps hormone deficiency of hypothalamic and/or pituitary origin is a more common sequel of acute meningoencephalitis than has hitherto been reported.

An evaluation of the thyrotrophin-releasing hormone stimulation test in paediatric clinical practice

AIM

The aim of this retrospective study was to evaluate the clinical usefulness of the thyrotropin-releasing hormone (TRH) test in children with suspected hypothalamic or pituitary dysfunction.

METHODS

We reviewed the case notes of all patients in whom a TRH test had been performed over a 6-year period. Group 1 (n = 85, 34 males, aged 0.9-18.8 years) was the reference group with no evidence of hypothalamic, pituitary or thyroid dysfunction. Group 2 (n = 42, 24 males, 0.1-18.0 years) were being investigated for possible pituitary or hypothalamic insufficiency.

RESULTS

In Group 1, thyrotropin (TSH) responses were higher in females than males (p < 0.01). In Group 2, TSH responses were normal for gender in 26 patients, subnormal in 5, and exaggerated/delayed in 11. Four patients with normal TSH responses and 4 with exaggerated/delayed responses had persistently low free thyroxine (FT(4)) or later developed low FT(4) and were treated with thyroxine. All those with subnormal TSH responses had normal FT(4) and were not treated. The TRH test did not reliably discriminate between hypothalamic and pituitary disorders.

CONCLUSIONS

The TRH test did not give useful clinical information. Clinical decisions regarding thyroxine treatment were based on FT(4), not the TRH test. The TRH test should be abandoned in paediatric practice.

Somatotroph to thyrotroph cell transdifferentiation during experimental hypothyroidism - a light and electron-microscopy study

Somatotroph and thyrotroph pituitary cells share a common precursor cell expressing the transcription factor Pit1 in ontogeny. Cells expressing both thyrotropin (TSH) and growth-hormone (GH) are found in adult rat pituitary and in human pituitary adenomas in acromegaly, and these tumors contain both thyrotropin-releasing hormone (TRH) and the TRH receptors (TRHR). It has been shown that stimulation of TSH expression in primary hypothyroidism promotes changes suggestive of somatotroph to thyrotroph cell transdifferentiation. We tested this hypothesis and the role of TRH in experimental primary hypothyroidism in rats. Adult female Long-Evans rats, 6 months old, were administered the antithyroid drug methimazole (0.1% w/v) in the drinking water for 42 days. Animals were sacrificed by perfusion fixation under anaesthesia at weekly intervals and pituitary tissue processed in acrylic resin for immunofluorescence and immuno-electronmicroscopy for TSH, GH and TRHR. In the hypothyroid rat pituitary immunofluorescent somatotrophs were greatly reduced in number and gradually replaced by thyrotrophs during methimazole administration. Colocalization of GH and TSH in the same cell was noted. Immunoelectronmicroscopy demonstrated the development of enlarged thyrotrophs with dilated rough endoplasmic reticulum containing an electron-dense material and intracisternal granules, both of which are immunoreactive for TSH ('thyroidectomy cells'). The somatotrophs showed reduced GH immunoreactivity and also the presence of TSH-type, small-size secretory granules. This suggests that the greatly increased number of TSH-cells in methimazole-induced-hypothyroidism is due, at least partially, to the transdifferentiation of somatotroph into thyrotroph cells. TRHR immunofluorescence was expressed in many somatotrophs in normal rat pituitary and unlike immunoreactive GH, its expression was enhanced during hypothyroidism. The number of TRHR-immunoreactive cells increased in parallel with the number of TSH-immunoreactive cells. This indicates a role for TRH stimulation in the transdifferentiation process. Taken together, these data suggest that, in addition to the cell mutation mechanism involving an early totipotential progenitor cell, transdifferentiation of existing somatotroph cells also plays a part in the pathogenesis of multihormonal GH-secreting adenomas.

Is the thyrotropin-releasing hormone test necessary in the diagnosis of central hypothyroidism in children

To determine the value of the TRH test, we analyzed the unstimulated serum T(4) and TSH concentrations in 54 children with central hypothyroidism. A TRH test was performed in 30 patients. Midline brain defects (septo-optic dysplasia, 28; holoprosencephaly, 2) and combined pituitary hormone deficiencies were present in 30 and 52 patients, respectively. The mean serum free T(4), total T(4), and basal TSH concentrations were 0.6 ng/dl, 4.0 microg/dl, and 2.8 microU/ml, respectively. Five patients demonstrated elevated basal serum TSH concentrations. A normal TRH test [increase (delta) in TSH, 4.5-17.8], based on data from 30 controls, was documented in 23.3% of patients. Brisk (deltaTSH, >17.8), absent/blunted (deltaTSH, <4.5), and delayed responses were documented in 16.7%, 30%, and 30% of patients, respectively. The mean age at diagnosis was 2.8 yr, with 8 patients evolving into TSH deficiency. It was not possible to differentiate patients as having pituitary or hypothalamic disease based solely on the TRH test results. Patients with septo-optic dysplasia were diagnosed earlier and had elevated basal serum TSH and PRL concentrations, diabetes insipidus, and evolving disease. Although full pituitary function assessment is mandatory to identify combined pituitary hormone deficiencies, a TRH test is not essential, and the diagnosis should be made by serial T(4) measurements.

[Thyroid function tests in viral chronic hepatitis]

BACKGROUND

One hundred and twenty five patients with virus B or C chronic active hepatitis and postnecrotic cirrhosis and different degrees of liver dysfunction were studied.

AIM

1) To determine a thyroid hormonal profile; 2) to evaluate the prognostic value of these tests in relation to the progression of the disease and mortality; 3) compare these findings with Child-Pugh classification.

PATIENTS AND METHODS

The patients were divided in four groups: a) 31 with chronic active hepatitis; b) 41 with postnecrotic cirrhosis Child A; c) 35 with postnecrotic cirrhosis Child B and d) 18 with postnecrotic cirrhosis Child C. The protocol comprised serum measurements of albumin and bilirrubin, estimates of prothrombin time and clinical evaluation of ascites and encephalopathy, measurement of total serum triiodothyronine, thyroxine, thyroid-stimulating hormone, free thyroxine, reverse triiosothyronine, calculated rT3/T3 index (IrT3) and thyrotropin-releasing hormone test.

RESULTS

Total serum triiodothyromnine showed the most significant difference among the groups, gradually lower as the disease became more advanced (CAH: 149.2 +/- 42.3 ng/dL; PNC-A: 137.4 +/- 37.2 ng/dL; PNC-B: 88.0 +/- 28.4 ng/dL and PNC-C: 41.8 +/- 21.9 ng/dL). Low levels of T4 (4.5 +/- 2.0 micrograms/dL) and FT4 (0.7 +/- 0.4 ng/dL) and elevated levels of thyroid-stimulating hormone (7.2 +/- 11.5 microIU/mL), reverse triiosothyronine (60.8 +/- 52.1 ng/dL) and calculated rT3/T3 index (2.2 +/- 2.6) were more frequent in patients with postnecrotic cirrhosis Child C. Thyrotropin-releasing hormone test was normal in the majority of the patients.

CONCLUSION

The present study shows a positive relationship between the low serum levels of T3 and elevated serum levels of rT3 and IrT3/T3 with the degree of hepatic dysfunction according to the Child-Pugh classification.

Serum thyroid-stimulating hormone measurement for assessment of thyroid function and disease

Third generation thyroid stimulating hormone (TSH) assays have emerged as the single most useful test of thyroid function, and are used widely and appropriately as a screening test. TSH measurement alone may be misleading in complicated patients and those undergoing treatment for thyroid dysfunction. Before obtaining thyroid function tests, clinicians need to consider whether the patient might have pituitary or hypothalamic disease or severe nonthyroidal illness, and whether assessment of the pituitary-thyroid axis reflects steady-state conditions. Subclinical hyperthyroidism is associated with adverse effects on the skeleton and the heart, and is best assessed by measurement of serum TsH with a third-generation assay.

Pattern of recovery of the hypothalamic-pituitary-thyroid axis following radioactive iodine therapy in patients with Graves' disease

PURPOSE

To characterize the time course of recovery of the hypothalamic-pituitary-thyroid (HPT) axis by determining the frequency, onset, duration, and clinical attributes of the central hypothyroid phase following 131I therapy for Graves' disease and to examine whether the central hypothyroid phase is due to direct pituitary thyrotroph suppression or to hypothalamic thyrotropin-releasing hormone (TRH) deficiency.

PATIENTS AND METHODS

Twenty-one hyperthyroid patients with Graves' disease evaluated at a university endocrine clinic and treated with radioactive iodine were prospectively studied. Serial thyroid function levels (serum thyroxine [T4], free thyroxine [free T4], triiodothyronine [T3], and thyroid-stimulating hormone [TSH]) were measured and TRH stimulation tests were performed at 2 to 4 week intervals for all subjects following 131I treatment. None of the patients was treated with thionamides after receiving 131I therapy.

RESULTS

Nineteen (90%) of the patients with Graves' disease experienced a transient central hypothyroid phase defined as the presence of a suppressed or inappropriately normal TSH level despite a low free T4 level following 131I treatment. This phase occurred a mean of 62.8 +/- 5.1 days following 131I treatment, persisted for an average of 24.7 +/- 2.4 days, and was not predictive of eventual treatment outcome. All patients had concordantly low T4 and T3 levels during this period and exhibited a blunted TSH response to TRH compared to 29 euthyroid control subjects, suggesting primary feedback suppression at the level of the pituitary thyrotrophs. The suppressed thyrotrophs required a minimum of 2 weeks to recover once patients became hypothyroid. The length of preexisting hyperthyroidism, basal free T4 elevation, and administered dose of 131I failed to predict the duration of the central hypothyroid phase, although a higher dose of 131I was associated with an earlier onset of central hypothyroidism (r = -.51, P < 0.05).

CONCLUSIONS

Clinicians should be aware of the delay in the recovery of the HPT axis that occurs in the majority of patients with Graves' disease treated with 131I and is manifested by a transient central hypothyroid phase. The blunted TSH response to TRH stimulation during this period suggests that suppression occurs primarily at the level of the pituitary thyrotrophs. The use of sensitive TSH measurements alone to monitor these patients during this period is not helpful and may be misleading.

Hypothalamic-pituitary dysfunction in patients with craniopharyngioma

OBJECTIVE

Previous studies of preoperative pituitary function in patients with craniopharyngioma have been limited in scope and have focused on children. We have evaluated the impact of craniopharyngiomas and their surgical treatment on pituitary function in a large group of mostly adult patients.

DESIGN

We performed a retrospective study of patients treated at our centre between 1980 and 1992.

PATIENTS

Twenty-two men and 13 women, most of them adults, treated surgically for craniopharyngioma during the above period.

MEASUREMENTS

Serum glucose, GH, LH, FSH, TSH and cortisol were measured both before and after a combined insulin induced hypoglycaemia, GnRH and TRH test. Basal concentrations of thyroid hormones, PRL and gonadal steroids were also measured. Preoperative computed tomographic scan was performed in all patients, and a detailed study of visual function before and after surgery was available for 32 of them. Endocrine function was reevaluated post-operatively.

RESULTS

In preoperative studies, 29 patients had some anterior pituitary deficit and 13 had diabetes insipidus. The most common abnormality was gonadotrophin deficiency, followed by GH deficiency. Dynamic studies suggested a hypothalamic origin for these deficits. In post-surgical evaluation, impaired pituitary function was observed in most patients. Panhypopituitarism was present in 28 cases and diabetes insipidus in 24.

CONCLUSIONS

Our report illustrates the high incidence of endocrine deficits in patients with craniopharyngioma. Additional hypothalamic-pituitary dysfunction usually occurs following surgical treatment of these tumours.

The evaluation of hypothalamic somatostatin tone using pyridostigmine and thyrotropin releasing hormone in patients with acromegaly

To indirectly evaluate the hypothalamic somatostatin (SS) tone in patients with acromegaly, the effects of pyridostigmine (PD), a cholinesterase inhibitor which can inhibit hypothalamic SS secretion, on TRH-induced TSH secretion and the effects of SMS 201-995 on TSH or GH secretion were studied in acromegalic patients (31-69 yr, n = 10), normal young (21-24 yr, n = 7) and normal old male subjects (62-71 yr, n = 7). After pretreatment with PD (60 mg po, -30 min), normal young subjects showed significantly enhanced TSH responses to TRH (500 micrograms i.v., 0 min) compared to single administration of TRH, whereas normal old and acromegalic patients did not show such enhancement. Plasma TSH response to a single administration of TRH in acromegalic patients was significantly lower than that of normal young and old subjects. Although normal young and old subjects showed significantly enhanced GH responses to GHRH (100 micrograms i.v. at 0 min) after the pretreatment with PD (60 mg, -30 min), no such enhancement was observed in acromegalic patients. In contrast, the decrement in plasma TSH after SMS 201-995 administration was similar between normal subjects (5 young 5 old) and 7 acromegalic patients. Further, the maximal plasma GH decrement after administration was significantly greater in acromegalic patients than in the 5 normal young and 5 old subjects p < 0.01). In conclusion, hypothalamic SS tone does not appear to be elevated in acromegalic patients compared to normal young and probably old subjects.

Magnetic resonance and the diagnosis of short stature of hypothalamic-hypophyseal origin

Magnetic resonance imaging was performed in 23 patients with short stature (7 had multiple pituitary hormone defect, 11 had isolated growth hormone deficiency and 5 had normal variant short stature) to investigate if there is a relation between magnetic resonance findings and results of endocrine tests. Magnetic resonance imaging of patients with multiple pituitary hormone deficiency or with serious isolated growth hormone deficiency (growth hormone < 3 micrograms/l) revealed an interrupted pituitary stalk and ectopic neurohypophysis or a mass. In patients with less serious isolated growth hormone deficiency (growth hormone > 3 micrograms/l) or with normal variant short stature, the technique revealed a normal or hypoplastic hypophysis. Magnetic resonance appears to be a useful second-level diagnostic tool in defining the type of alteration in growth defects of endocrine origin.

Simultaneous occurrence of transient resolving thyrotoxicosis due to painless thyroiditis, hypopituitarism and diabetes insipidus following pituitary apoplexy

A rare case of concomitant association of transient thyrotoxicosis due to painless thyroiditis, hypopituitarism and central diabetes insipidus following spontaneous pituitary apoplexy is presented.

The effect of calcitonin on growth hormone secretion in acromegaly

To determine whether human calcitonin inhibits GH secretion in acromegaly, as previously described for healthy subjects, the effect of an i.v. bolus injection of calcitonin or saline on GH levels in patients with active acromegaly was studied and compared to that of an i.v. bolus injection of the synthetic somatostatin analogue, octreotide. After the injection of calcitonin, GH levels decreased by 46% of initial values, whereas octreotide reduced GH levels by 87% and saline had no significant effect. Administration of calcitonin to acromegalics did not cause the transient rise in plasma PRL and TSH levels seen in normal subjects. Octreotide induced a decrease in plasma PRL in three out of seven patients. It is concluded that human calcitonin suppresses GH secretion in acromegaly, but not to normal levels; moreover the effect is less than that found for octreotide. In addition, acromegalic patients did not exhibit the PRL and TSH-releasing activity of calcitonin found in normal subjects, while octreotide inhibited PRL secretion in some acromegalic patients.

The influence of diabetes mellitus on thyrotropin response to thyrotropin-releasing hormone in untreated acromegalic patients

Impairment of thyrotropin (TSH) response to thyrotropin-releasing hormone (TRH) has been documented in patients with uncontrolled diabetes mellitus (DM). In acromegalic patients, however, there have been no data regarding TSH secretion studied taking the existence of DM into consideration. Therefore, we investigated the TSH response to TRH [expressed as TSH increment (delta TSH)] in 14 untreated acromegalic patients, who did not show the suprasellar extension of adenoma, divided into two groups on the basis of either presence or absence of uncontrolled DM, and in 28 normal subjects. The mean max delta TSH was significantly reduced (p less than 0.02) in acromegalic patients despite similar mean serum T4 and free T4 index (FT4l) levels. Furthermore, the mean basal and max delta TSH in 7 patients with DM (FBS, 120-300 mg/dl; HbA1, 8.8-15.2%) were significantly lower than those in 7 patients without DM (p less than 0.05 and p less than 0.02, respectively) despite similar the mean serum T3, T4, FT4l, growth hormone (GH) and prolactin (PRL) levels and sellar volume. In 4 patients with DM the TSH response to TRH 6-8 weeks after insulin therapy, when their HbA1 levels were normal, increased compared to that before insulin therapy. The mean max delta TSH after selective adenomectomy in 8 patients (3 in DM group and 5 in non-DM group), whose fasting basal GH fell to less than 5 ng/ml, was almost identical to that in normal subjects. In conclusion, the present study suggests that the abnormality in TSH secretion in acromegalic patients may be increased by the existence of uncontrolled DM.

Symptomatic hypothalamic-pituitary dysfunction in nasopharyngeal carcinoma patients following radiation therapy: a retrospective study

Endocrine assessment was performed in 32 relapse-free southern Chinese patients (21 males and 11 females, aged 27-50 years at the time of assessment) 5-17 years following radiation therapy (RT) alone for early nasopharyngeal carcinoma (NPC). Initial screening was done using questionnaires emphasizing on impaired sexual function and menstrual disturbance plus measurement of serum levels of thyroxine, free thyroxine index, thyrotropic hormone, prolactin, and additionally testosterone for males only. Those showing abnormalities were subjected to detailed pituitary function tests. Hypothalamic-pituitary dysfunction was found in 7 female patients and only 1 male patient. A delayed TSH response to thyrotropin releasing hormone suggesting a hypothalamic disorder was seen in 6 of the affected female patients, and hyperprolactinaemia in also 6. None of the patients had evidence of diabetes insipidus. Hypopituitarism became symptomatic 2-5 years after RT with a mean latent interval of 3.8 years. A practical protocol for regular endocrine assessment for NPC patients after RT has been proposed. Multiple linear regression analysis of the radiotherapeutic data from the 11 female patients indicates that the likelihood of late occurrence of symptomatic hypothalamic-pituitary dysfunction following RT is dependent on the TDF of the target dose to the nasopharyngeal region and the height of the upper margin of the opposed lateral facial fields above the diaphragma sellae (coefficient of multiple correlation = 0.9025). Except when the sphenoid sinus or the middle cranial fossa is involved, it is advisable to set the height of the upper margin of the lateral facial field at a level no higher than the diaphragma sellae. The hypothalamus and possibly the pituitary stalk as well may sustain permanent damage by doses of radiation within the conventional radiotherapeutic range for carcinomas.

Hypothalamic hypopituitarism following cranial irradiation for nasopharyngeal carcinoma

Eight patients, one male and seven females, with no pre-existing hypothalamic-pituitary disease, who developed symptoms of hypopituitarism following cranial irradiation for nasopharyngeal carcinoma were studied 5 years or more after radiotherapy. All were GH deficient. Four of the patients with no GH response during insulin tolerance tests (ITT) showed increased GH in response to synthetic human growth hormone releasing factor (GRF-44). Four patients had impaired cortisol responses to ITT, and gradual but diminished cortisol responses to ovine corticotrophin releasing factor (CRF-41). There was no significant difference between mean peak increments in response to ITT and those in response to CRF-41. TSH responses to TRH were delayed in five and absent in two patients; four of these had low free T4 index. Prolactin was raised in all seven women and increased further in response to TRH. Two patients had impaired gonadotrophin responses to LHRH. None of the patients had clinical or biochemical evidence of diabetes insipidus. These data suggest that post-irradiation hypopituitarism in these patients results from radiation damage to the hypothalamus leading to varying degrees of deficiency of the hypothalamic releasing or inhibitory factors.

Exaggerated response of thyrotropin to thyrotropin-releasing hormone in patients resected for Crohn's ileitis

We have studied the response of thyrotropin to exogenous thyrotropin-releasing hormone in 13 patients who had previous intestinal resection for Crohn's disease, and in 42 healthy controls. An exaggerated and prolonged response curve was found in eight of the patients and one control (P less than 0.01), while baseline hormone levels were normal in all. These results may be related to the state of iodine deficiency known to develop in inflammatory bowel disease, but the pathophysiology requires further elucidation.

Endocrine profiles in pediatric andrology. I. Thyroid-stimulating hormone response to thyrotropin-releasing hormone in normal and protein-calorie malnourished infants

Thryotropin-releasing hormone (TRH) was intravenously administered to eight normal control infants and ten infants with kwashiorkor. Stimulation caused by TRH was measured at various time intervals. The basal total protein mean value +/- SE was 6.9 +/- 0.3 and 4.0 +/- 0.3 g/dl for the control and kwashiorkor groups, respectively. Serum total thyroxine was 7.7 +/- 0.6 and 4.8 +/- 0.8 micrograms/dl for the control and kwashiorkor groups, respectively. Serum levels of thyroid-stimulating hormone (TSH) were 3.2, 13.5, 9.0, 7.4, and 8.0 microU/ml for the controls before stimulation and 20, 60, 90, and 120 min after stimulation, respectively. The corresponding values for the infants with kwashiorkor were 5.7, 13.9, 14.9, 15.2, and 15.3 microU/ml, respectively. The delayed TSH response to TRH stimulation in the infants with kwashiorkor was attributed to disturbance in the hypothalamic-pituitary-thyroid axis.

Response to TRH in suspected hypopituitarism

A retrospective analysis was made of 405 thyrotrophin-releasing hormone (TRH) stimulation tests on children who were successful applicants for growth hormone (GH) therapy in the UK between 1977 and 1981 inclusive. Thyroid-stimulating hormone (TSH) responses to TRH were divided into normal and those indicating pituitary or hypothalamic disease on the basis of criteria which eliminated variation in TSH assay between laboratories. Among children known to be hypothyroid 93% had abnormal TRH stimulation tests, but 35% of those children who were clinically euthyroid and who had normal serum thyroxin levels also had abnormal TSH responses to TRH. Abnormal TRH tests in the latter group were most common in euthyroid children who had GH deficiency with clearly defined aetiology and least common in those with idiopathic GH deficiency. Further work is required to clarify the interpretation of an abnormal TRH stimulation test in this group of children, but until this is done, such patients should be kept under regular review with respect to thyroid function.

External pituitary irradiation as a cause of TRH deficiency in patients with pituitary adenomas

The influence of external pituitary irradiation (XRT) on thyrotroph function and PRL secretion was studied in twenty-five patients with pituitary adenomas, of whom eight had acromegaly. Twenty-one patients had undergone subtotal operative removal of their adenomas 8-190 weeks (median 12 weeks) before XRT. Following irradiation there was a significant reduction in peak serum TSH levels in response to i.v. TRH (P less than 0.05, compared with before XRT). Peak TSH levels returned to normal at 3 months. Similarly a transient reduction in TRH-stimulated beta-TSH release was observed. Serum T3 and T4 concentrations also fell after XRT, the levels at 3 months being significantly lower than control values (P less than 0.02), though no difference was seen at 6 and 12 months. A delayed (hypothalamic) serum TSH response to TRH (60 greater than 20-min level) developed at 6 months. In contrast, PRL concentrations (basal and TRH stimulated) were not altered during the 12 months following XRT. These findings demonstrate that thyrotroph function can be transiently impaired following external pituitary irradiation. None of the patients studied required T4 replacement therapy. The development of a delayed TSH response to i.v. TRH may indicate endogenous TRH deficiency. It was not associated with supra-sellar tumour enlargement in our patients and may be due to hypothalamic damage by irradiation.

Pituitary-thyroid axis after bilateral orchiectomy in men

The functional interaction between the testis and thyroid was evaluated in 13 patients affected by prostatic carcinoma before and after bilateral orchiectomy. Two different patterns of thyroid hormones were noted. Immediately after surgery, free thyroxine (T4) increased and total triiodothyronine (T3) decreased probably as a result of surgical stress at anesthesia. Later, free T4 levels decreased while total T4 and thyroxine binding globulin (TBG) were unchanged. Such changes may be due to qualitative changes in binding proteins.

Autonomous thyroid nodules in adolescents: clinical characteristics and results of TRH testing

Seven adolescents with autonomous thyroid nodules were evaluated over a three-year period. They had hyperfunctioning nodules on radionuclide scan which failed to suppress with exogenous administration of thyroid hormone. They were clinically euthyroid and had normal T4, free T4, and basal TSH values. However, as a group they had elevated total serum T3 concentrations, blunted TSH response to TRH, and accelerated closure of cranial sutures, all of which suggested subtle hyperthyroidism. These patients have been followed for one to five years. Four have undergone partial thyroidectomy because of persistent elevation in the serum T3 concentration or enlargement of the nodule. The clinical presentation and laboratory findings in this group are similar to those found in adults with autonomous nodules.

Delayed TSH release in anorexia nervosa following injection of thyrotropin-releasing hormone (TRH)

We studied plasma concentrations of thyrotropin (TSH), prolactin and growth hormone (GH) after injection of 500 microgram of thyrotropin-releasing hormone (TRH) in 10 patients with acute anorexia nervosa, subsequent to initial nutritional stabilization and again after weight recovery. Plasma thyroxine levels were normal throughout, whereas plasma triiodothyronine levels were low initially but rose with weight gain. The TSH secretory response to TRH was delayed and prolonged during the initial study but showed a normal overall quantitative response, except for two patients who showed no TSH rise. Following weight gain the TSH response was more rapid, and positive correlations were found between body weight and peak TSH levels and rapidity of TSH response. Six of 10 patients, however, continued to exhibit a delayed TSH peak response, the average response was markedly increased in comparison with that in normal females. The prolactin response curves were normal at both times. Rises in GH following TRH were observed in two patients prior to and in one patient after weight gain. We conclude that acute anorexia nervosa, with its concomitant profound weight loss, is accompanied by abnormalities in the hypothalamo-pituitary-thyroid axis, which are reversed only in part with improvement in the illness and weight gain, suggesting the persistence of disordered neuroendocrine function in this illness.

Impaired dopaminergic control of thyroid stimulating hormone secretion in chronic renal failure

After administration of intravenous metoclopramide, a dopaminergic receptor blocking agent, no rise in thyroid stimulating hormone (TSH) could be found in patients with chronic renal failure, in contrast to non-uraemic controls. Basal TSH values were normal in the uraemic patients but the TSH response to thyrotrophin-releasing hormone (TRH) was significantly reduced. These results suggest that a discrete abnormality in the hypothalamo-pituitary axis exists in uraemia which may in part be due to interference with central dopaminergic control by a uraemic toxin.

Studies of hypothalamic function in Huntington's chorea

In eight patients with classical Huntington's chorea hypothalamic function was assessed by the insulin tolerance test, the thyrotrophin releasing hormone test, the gonadotrophin releasing hormone test and water deprivation and the results compared with those of 10 control subjects. All patients ceased to have choreiform movements for approximately 60 minutes during the insulin tolerance test. Four of the patients failed to show clinical features of stress in response to hypoglycaemia. The fasting blood glucose level and blood glucose response to insulin were similar for the two groups. However, the response of plasma cortisol (p less than 0.05) and of growth hormone (p less than 0.05) to hypoglycaemia was earlier in patients than controls, though peak responses were the same for each group. The thyrotrophin releasing hormone test revealed no difference in basal levels of thyroid stimulating hormone in either group, or in peak response to thyrotrophin releasing hormone or in the increment at 20 minutes. One of the patients had a delayed response typical of a hypothalamic disorder, whereas none of the controls had such a response. Mean free thyroxine index levels for each group were similar. There was no difference in basal prolactin level, or in the increment or in the peak level in response to thyrotrophin releasing hormone between each group as a whole or when the males and females were analysed separately. Because of small subgroups, the data from the gonadotrophin releasing hormone test were difficult to analyse, but no clear differences or obvious abnormalities emerged. Water deprivation revealed no evidence of inability to concentrate urine in either group and hence no indication of impaired antidiuretic hormone function. The study supports previous findings of altered hypothalamic function in patients with Huntington's chorea but further suggests that serotoninergic rather than dopaminergic mechanisms may be altered.

Pituitary function tests in Sheehan's syndome

Fourteen patients with a typical history of Sheehan's syndrome underwent pituitary function tests with simultaneous injections of 100 micrograms LH-RH, 200 micrograms TRH and 0.05--0.1 units of soluble insulin per kg body weight. Serum prolactin levels remained unchanged in all of eleven subjects given TRH. GH levels did not rise after hypoglycaemia in five subjects. In contrast serum LH and FSH rose significantly in twelve out of fourteen subjects given LHRH and serum TSH rose significantly in five out of seven subjects given TRH. It is concluded that pituitary function is relatively preserved for LH and FSH but not for prolactin and GH in Sheehan's syndrome. It is further suggested that absence of a rise in prolactin following TRH stimulation may provide the most sensitive test of pituitary hypofunction in postpartum haemorrhage.

Amyloid goitre in familial Mediterranean fever

Three patients known to suffer from familial Mediterranean fever (FMF), systemic amyloidosis and chronic renal failure developed large amyloid goitres. Amyloid goitre is an extremely rare complication of systemic amyloidosis not previously described in FMF. The clinical and pathological features of these three cases were similar to those previously described in amyloid goitre. In two of the patients abnormalities in thyroid function were consistent with those documented in chronic renal failure. There was evidence of hypothyroidism in a third patient. There was no evidence of amyloid induced dysfunction of other endocrine organs.

Function of the hypothalamo-hypophysial-thyroid axis in chronic renal failure

Hypothalamo-hypophysial-thyroid function has been studied in twenty-five patients with chronic renal failure. Eight were receiving conservative treatment, nine peritoneal dialysis and eight haemodialysis. All were clinically euthyroid. Total thyroxine (T4) and triiodothyronine (T3) levels were reduced but free T4 levels were normal, while free T3 was reduced in patients with the most severe renal failure. It is suggested that the binding of thyroid hormones by the transport proteins is reduced and that peripheral conversion of T4 to T3 is impaired in renal failure. The thyrotrophin response to thyrotrophin-releasing hormone (TRH) is reduced in renal failure but this reduction is probably independent of alterations in thyroid hormone metabolism. Growth hormone was released by TRH in seven of the patients studied, possibly as a result of protein malnutrition.

Pre- and postoperative evaluation of hypothalamo- pituitary function in children with craniopharyngiomas

Pre- and postoperative evaluation of hypothalamic-pituitary function was performed in six children, aged 5.5 to 13.3 years with craniopharyngiomas. Before surgery growth hormone deficiency (GHD) was documented in four, hypothalamic hypothyroidism in three, and secondary ACTH-deficiency and hyperprolactinaemia in one patient. Diabetes insipidus was absent in all patients. After neurosurgical treatment GHD was present in all, hypothyroidism in five, ACTH-deficiency in three, hyperprolactinaemia in three, and diabetes insipidus in four children. The study shows that all endocrine functions tested may be defective even before surgery, although diabetes insipidus seems to be a rare preoperative complaint. Surgical intervention, however, often leads to additional endocrine disorders. From the data presented here one may suggest that TRH stimulation tests, evaluation of serum prolactin, and lysin-vasopressin stimulation tests are the most useful investigations to distinguish between hypothalamic and primary pituitary disorders.

Pituitary microadenoma: diagnostic studies

Forty-one women with oligo-menorrhoea and/or galactorrhoea were subjected to hypothalamic pituitary-thyroid testing in an attempt to establish the presence or absence of an underlying pituitary microadenoma. They were divided into two groups in accordance with the serum level of prolactin (PRL): Group I (N = 25, mean +/- SE 17.6 +/- 1.5 ng/ml) and Group II (N = 16, 102.8 +/- 29.7 ng/ml). The dynamic tests performed were a TRH test, a stimulation test with metoclopramide (MCP) and a suppression test with bromocriptine. The results of these tests were compared with those obtained in nine normal women and eleven patients with surgically proved pituitary microadenoma. Radiologically abnormal pituitary fossas were found in ten subjects from Group I and in fourteen from Group II. All patients were euthyroid. A persistently elevated serum TSH in response to TRH was observed in patients of Group II suggesting an hypothalamic abnormality and a progressive decrease in the 120-min use of serum T3 was noted with increasing evidence of the existence of a pituitary tumour. A negative correlation was found between the basal serum PRL and the rise of serum PRL with TRH. Patients from Group II showed a lower PRL response to MCP when compared to Group I and again a negative correlation between basal level of serum PRL and the change after MCP was observed. No clear difference in the 4-h response to bromocriptine was found between the different groups of subjects. In conclusion, none of the three tests analysed permitted us to establish which of the patients had an underlying pituitary microadenoma.

[Diagnostic procedures in diencephalo-hypophyseal insufficiency (author's transl)]

A functional diagnosis of the diencephalohypophyseal system was carried out in patients with Sheehan syndrome, chromophobic adenoma, craniopharyngioma, prolactin-producing pituitary tumours, acromegaly, hypothalamo-pituitary dwarfism and constitutional retardation. A combined insulin hypoglycaemia/LH-RH/TSH test was performed to define frequency and extent of anterior pituitary insufficiency. With these illnesses, almost generally, a somatotropic insufficiency (except in acromegaly) was found. An impairment of gonadotropic function was often present, in general a pathologic LH-RH test correlating with a more or less developed androgen deficiency. An adrenocorticotropic insufficiency was found in most patients with sheehan syndrome, chromophobic adenoma and craniopharyngioma while in acromegaly and hypothalamo-pituitary dwarfism it was present less frequently, necessitating a substitution with corticoids. The TRH test reflects only incompletely a secondary hypothyroidism, and can be normal with organic processes of the diencephalo-hypophyseal region, making a T3 and T4 estimation in the blood decisive for a thyroid hormone substitution. A clear-cut separation of the hypothalamic from the pituitary cause of the insufficiency is neither possible with the LH-RH nor with the TRH test.

XY gonadal dysgenesis associated with hGH and gonadotrophin deficiencies

A girl of remarkably short stature, referred for investigation with the diagnosis of gonadal dysgenesis and the finding of a male karyotype, proved to be deficient in growth hormone and gonadotrophin secretion, and was treated with growth and sex hormones. It was concluded that this case demonstrates an apparently casual coincidence of pituitary insufficiency with XY gonadal dysgenesis, evidently the first to be reported.

Amenorrhoea, body weight and serum hormone concentrations, with particular reference to prolactin and thyroid hormones in anorexia nervosa

Twenty women with anorexia nervosa were investigated at varying stages during weight gain. Basal prolactin and TSH and prolactin responses to TRH were normal and unrelated to body weight. LH, FSH and 17 beta oestradiol were low in emaciated patients and rose with weight gain. There was no correlation between serum gonadotrophin and prolactin concentrations. T3 and T4 concentrations were low but T3 rose with weight gain during refeeding over 4-6 weeks, whereas T4 remained low. A positive correlation was found between the TSH response to TRH and body weight. The abnormalities in the hypothalamic-pituitary-thyroid axis were similar to those seen in a variety of chronic illnesses and appear to be unrelated to the amenorrhoea. The failure of restoration of normal function at least after short-term refeeding requires further investigation. It was concluded that the amenorrhoea in anorexia nervosa is not associated with changes in prolactin secretion but is determined primarily by changes in the hypothalamic-pituitary-gonadal axis. These changes are induced largely by nutritional factors but psychological factors may also be involved.

Assessment of pituitary function

Sellar and parasellar tumours comprise 10-15% of all intracranial neoplasms. Neurologists will this often be faced with the problem of assessing pituitary function. A thorough clinical examination is of the foremost importance. In addition a small number of simple and rapid tests is required. Knowledge of the physiological variation in pituitary function is, however, necessary to allow a safe interpretation of the results. A simple routine procedure for assessing pituitary function is proposed.

Comparison of long-acting analogues of luteinizing hormone releasing hormone in man

Currently, LHRH, when used therapeutically, is given by parenteral injection every 8 h. We have looked at the release of LH and FSH induced by five analogues of LHRH and compared this with gonadotrophin release after synthetic LHRH. The analogues were substituted in position 6 or in positions 6 and 10 and were given intravenously, intranasally or subcutaneously in three separate studies. After intravenous administration of 100 micrograms, all analogues caused greater release of LH and FSH than did synthetic LHRH. Given intranasally in a dose of 500 micrograms, three of the four analogues tested caused greater LH and FSH release than did LHRH. With tryptophan substitution in position 6 (D-TRP6-LHRH), mean LH levels in five subjects were still above the normal range 24 h after a single intranasal dose. The intranasal administration of selected analogues of LHRH has great potential in the treatment of conditions associated with deficient gonadotrophin secretion, provided that pituitary overstimulation, which may eventually lead to a decrease in LH and FSH output by the anterior pituitary, is avoided.

Hypothalamo-pituitary-thyroid function in anorexia nervosa: influence of weight gain

The functional state of the hypothalamo-pituitary-thyroid axis was assessed in 14 women and girls with anorexia nervosa when at low body weight and again in 12 cases after they had gained weight. Mean serum thyroxine concentrations were low before and after weight gain. Mean serum triiodothyronine (T3) concentrations were substantially reduced at low weight and doubled after weight gain, the absolute values being linearly correlated with body weight expressed as a percentage of the ideal. Concentrations of reverse T3 were greatly increased in some patients initially and fell with weight gain. Basal concentrations of thyroid-stimulating hormone (TSH) were unchanged after weight gain but the TSH response to thyrotrophin-releasing hormone was significantly augmented; delayed patterns of response were found in seven out of 12 patients tested before and three out of 12 patients tested after weight gain. Changes in the hypothalamo-pituitary-thyroid axis are common in anorexia nervosa and probably represent both peripheral and central adaptations to the altered nutritional state.

Thyroid function in children with growth hormone deficiency, either idiopathic or caused by diseases of the central nervous system

Thyroid function was assessed in thirty two patients with growth hormone deficiency (GHD) by clinical examination and by measurement of T4-levels, free T4-indices, basal TSH values and TSH responses to TRH (100 mu/m2). Sixteen patients (50%) were hypothyroid. In thirteen patients, the endocrine disorders were considered to be of hypothalamic origin. Ten of them showed prolonged responses to TRH and in the other three the responses were exaggerated. In three patients hypothyroidism was due to a primary pituitary disorder. Sixteen patients were euthyroid although three of them showed impaired TSH responses. In the cases with idiopathic hypopituitarism (n = 20) there a high incidence of abnormal births in the children with additional hypothalamic hypothyroidism, but not in the euthyroid patients. It is concluded that in patients with previous breech or vacuum extraction delivery, growth hormone deficiency when combined with hypothalamic hypothyroidism may be due to birth trauma.

Thyrotropin and prolactin in patients with hypothalamus-pituitary diseases

Seventy patients with hypothalamus-pituitary diseases were studied. 13 of them were studied before surgical treatment and then 15-20 days and 6 months later. A comparison was made with 59 controls. In all these subjects PRL and TSH were studied under basal conditions and after TRH stimulation. As for TSH the highest percentage of abnormal responses was found in the group of patients with chromophobe adenoma and parasellar dysplasias. This area of the pituitary appears relatively undamaged in acromegalic patients. In clinically hypothyroid patients, normal or high TSH responses to TRH were often found. As for PRL, a hyperprolactinaemia was mostly found in the group of patients with chromophobe adenoma, parasellar dysplasias and craniopharyngioma, although there was a different pattern in the TSH responses. No correlation was found between the basal PRL levels and the TSH responses to TRH. There was no significant difference in the TSH responses of the patients with PRL secreting and non-secreting chromophobe adenomas. The hypothesis of two autonomous systems is supported by the finding of differences in the functional recovery of the two pituitary areas studied at different times after surgical treatment.