The TRH test in normal subjects: methodological considerations

The influence of 4-week treatment with sertraline on the combined T3/TRH test in depressed patients

In the present study, the influence of a 4-week treatment with sertraline on the regulation of hypothalamic-pituitary-thyroid (HPT) axis activity in depression was investigated, in particular the impact of sertraline on the thyroid receptor (TR)-mediated negative feedback control as measured by the combined T3/TRH test. In 20 drug-free patients (8 men, 12 women) suffering from a major depressive episode according to DSM-IV criteria the single TRH-stimulation test (administration of 200 microg TRH at 09:00h) was carried out followed by a combined T3/TRH test (pre-treatment with 40 microg 3,5,3'-triiodothyronine [T3] the night before; administration of 200 microg TRH at 09:00h the next day). After 4 weeks of treatment with sertraline at a standard dosage of 50 mg/day, both the single TRH test and the combined T3/TRH test were repeated in the depressed patients. Using repeated-measures ANOVA for statistical analysis, antidepressant therapy with sertraline did not have any significant impact on the TRH-induced TSH and prolactin stimulation (deltaTSH, deltaPRL) during the single TRH test nor during the combined T3/TRH test, neither in responders (n = 10) nor in non-responders (n = 10). Moreover, the percentage suppression of TRH-induced TSH stimulation (deltaTSH) after pre-treatment with 40 microg T3 was comparable before (-61.07%) and after the 4-week treatment with sertraline (-58.92%). Apparently, the therapeutic efficacy of antidepressants such as sertraline is not related to the regulation of HPT axis activity in depressed patients.

The combined T3/TRH test in depressed patients and healthy controls

It is well established that depressed patients show a blunted TSH response in the TRH-stimulation test. However, it has not been investigated so far whether pre-treatment with 3,5,3'-triiodothyronine (T3) is able to further suppress the TRH-induced TSH response in depressed patients or whether it may cause an escape-phenomenon with paradoxically enhanced TSH stimulation in a subsequent TRH test. In 20 drug-free depressed patients (eight men, 12 women) suffering from a major depressive episode according to DSM-IV criteria and in 20 age- and sex-matched healthy controls, the single TRH-stimulation test (administration of 200 microg TRH at 09:00 h) was carried out followed by a combined T3/TRH test (pre-treatment with 40 microg T3 at 23:00 h the night before; administration of 200 microg TRH at 09:00 h the next day). Compared to the controls, the depressed patients showed a significantly blunted TSH response in the single TRH test. However, the percentage suppression of TRH-induced TSH stimulation after pre-treatment with 40 microg T3 was comparable in the depressive patients (61.07%) and the healthy volunteers (64.20%). Prolactin secretion did not differ between patients and controls either in the single TRH test or in the combined T3/TRH test. Apparently, in contrast to the hypothalamo-pituitary-adrenocortical (HPA) system, no disturbance of feedback control in regulation of the hypothalamo-pituitary-thyroid (HPT) axis secretion can be demonstrated in depressed patients when using the combined T3/TRH test.

Acquired prolactin deficiency indicates severe hypopituitarism in patients with disease of the hypothalamic-pituitary axis

OBJECTIVE

Prolactin deficiency has been the subject of many scientific studies, but there is a paucity of information regarding prolactin deficiency in humans. In this report, adults with disease of the hypothalamic-pituitary axis (HPA) were studied to determine the prevalence of severe acquired prolactin deficiency (APD) and the pathophysiological characteristics associated with it.

PATIENTS AND METHODS

APD was defined as a serum prolactin level persistently below the detection limit of the assay, i.e. less than 50 mU/l (normal range: male 85-444, female 85-530). Patients with a diagnosis of acromegaly, prolactinoma or with congenital or drug induced prolactin deficiency were excluded. Three hundred and sixty-nine patients (190 women, age range 17-79 years) with disease of the HPA, meeting the specified criteria were identified.

RESULTS

Twenty-two (13 women, age range 29-76 years), showed evidence of APD. Thirteen of the 22 patients with APD had been treated for Cushing's disease. In all, 62 patients treated for Cushing's disease were identified, resulting in a prevalence of APD in treated Cushing's disease of 20.97%. Excluding treated Cushing's disease, the prevalence of APD in the remainder of the cohort was 2.93%. Nineteen patients with APD (86.4%) and 183 without APD (52.7%) underwent surgery in the region of the HPA (P = 0.0042). In contrast, nine patients with APD (40.9%) and 283 without APD (80.4%) had received radiotherapy, with fields which included the HPA (P < 0.001). No patient with isolated APD was identified. All patients with APD had evidence of severe GH deficiency (GHD) with a peak GH response to provocative stimuli of < 1.6 mU/l and a median IGF-I standard deviation score (SDS) of -4.85 (quartiles -9.56 to -2.80). Of the 13 patients with APD and Cushing's disease, all were gonadotrophin and TSH-deficient, six were adrenocorticotropic hormone (ACTH)-deficient and six (46.1%) had cranial diabetes insipidus (CDI). Of the remaining nine patients with APD, total anterior pituitary hormone failure was present in all and CDI was present in two (22.2%).

CONCLUSIONS

The presence of APD indicates severe hypopituitarism in adults with HPA disease. It is universally associated with severe GHD. It is more common after surgery to the HP region. It has a low overall prevalence except in patients surgically treated for Cushing's disease.

Subclinical hypothyroidism: a review of neuropsychiatric aspects

The authors review current information about the prevalence, causes, course, and consequences of subclinical hypothyroidism. There is evidence that subclinical hypothyroidism may be associated with cognitive dysfunction, mood disturbance, and diminished response to standard psychiatric treatments. Recommendations are presented for the screening, evaluation and treatment of patients in whom subclinical hypothyroidism may be contributing to neuropsychiatric dysfunction.

The thyrotropin-releasing hormone test: some statistical considerations

Final conclusions and data comparisons from the thyrotropin-releasing hormone (TRH) test results are made difficult by differences in test implementation methods,ie, TRH different administration routes, dosages and blood sampling times. A number of statistical analyses are feasible, which may also influence test interpretation. The authors review some types of statistical analyses and suggest using the area under curve (AUC) method as a means of evaluation. The TRH test was performed before treatment and after a 5-day wash-out period, in 40 depressed patients hospitalized in the Psychiatric Unit of Besancon Teaching Hospital (Centre Hospitalier Universitaire de Besançon). Variation analyses performed by peak and threshold comparison (7.0 IµU/ml) and by the AUC method (386 IµU/ml) in positive and negative patients revealed some statistical differences.

A kinetic study on secretion and elimination of endogenous thyrotropin in the thyrotropin-releasing hormone test

Serum thyrotropin (TSH) concentrations in normal young men were measured by a high-sensitivity immunoradiometric assay before and after intravenous administration of 500 micrograms of TSH-releasing hormone (TRH). A kinetic model was applied to evaluate the secretion rate both before (V0) and after (V0 + V* at maximum rate) the administration of TRH, the elimination constant (K), the latent time (L) between TRH administration and start of the stimulated secretion, and the total amount of TSH (T) released in response to TRH. V0, V* and T varied widely from individual to individual, but correlated well with TSH before TRH administration (r = 0.93, 0.80 and 0.87, respectively). A few minutes (1.89 +/- 1.30 min) after the administration of TRH, the secretion of TSH (0.025 +/- 0.016 microU/min ml) was stimulated, and the total release over about 1 h was 12.5 +/- 5.6 microU/ml. Serum TSH was maximum at 31.5 +/- 5.7 min. The half-time of disappearance of TSH was 42 +/- 9 min. These data confirm that the stimulated secretion continues for more than 30 min, and that the pituitary releases 43.2 +/- 22.9 mU of TSH (assuming the distribution volume of TSH is 5.8% of body weight) in response to TRH, an amount which correlates closely (r = 0.91) with TSH before TRH administration.

TRH: behavioral and endocrine effects in man

1. The tripeptide TRH exerts a spectrum of biological activities in both animals and man. Some of these activities have been extensively studied, particularly in psychiatric patients. 2. Behaviorally, TRH appears to increase the sense of well-being, motivation, relaxation, and coping capacity in both normal subjects and patients with psychiatric and neurologic disease. These effects are not disease-specific; attempts to use TRH as a treatment tool have thus been disappointing. 3. Endocrinologically, administration of TRH stimulates the response of TSH; this response has been reported to be blunted in approximately 30% of patients with major depression. However, TSH blunting is not specific for depression, it has also been observed in a variety of other psychiatric conditions. 4. The relevance of these effects for psychiatry in general, and for psychoneuroendocrinology especially, is discussed in this review.

Kinetic modeling of hormone release: application to time-averaged met-enkephalin release

The time course of hormone concentrations in response to a stimulus can be characterized with kinetic methods to express rates of hormone release and elimination, total amount of hormone release and expected best times for blood sampling. Routine application of kinetic methods should increase the sensitivity and applicability of hormonal challenge tests. Applications to the TRH test and to prolactin release measurements are reviewed. A new kinetic model for continuously collected samples is applied to measurements of met-enkephalin release in rats. Calculations indicated an initial concentration of 1876 pg/ml and a ventricular volume of distribution of 0.25 ml. After exposure of rats to nitrous oxide, the rate of release of met-enkephalin-like activity into the ventricles rose from 3.4 to 8.3 pg/min.

Neuroendocrine aspects of primary endogenous depression--IV. Pituitary-thyroid axis activity in patients and matched control subjects

In order to ascertain the extent of hypothalamo--pituitary--thyroid (HPT) axis dysfunction in endogenous depression, we determined nocturnal serum thyrotropin (TSH) concentrations, TSH responses to thyrotropin releasing hormone (TRH) administration, and serum triiodothyronine (T3) and thyroxine (T4) concentrations in 40 Research Diagnostic Criteria primary, definite endogenous depressives and 40 individually matched normal control subjects. We also examined the relationships of the HPT measures to pre- and post-dexamethasone (DEX) serum and urine cortisol measures and, in the patients, to subject characteristics, the diagnosis of endogenous/melancholic depression by different systems, and the overall severity and specific dimensions of depressive symptomatology. Compared to their matched controls, the patients showed significant reductions in nocturnal serum TSH and serum T3 concentrations. Neither the TSH responses to TRH nor serum T4 concentrations were significantly different between the two groups of subjects. In the patients, none of the subject characteristics, diagnostic schemes for endogenous/melancholic depression or specific aspects of depressive symptomatology were significantly related to HPT activity. The measures of HPT activity were unrelated to measures of hypothalamo--pituitary--adrenal cortical (HPA) axis activity in both groups of subjects.

Effects of age and diagnosis on thyrotropin response to thyrotropin-releasing hormone in psychiatric patients

The thyrotropin (thyroid-stimulating hormone; TSH) response to thyrotropin-releasing hormone (TRH) was studied in 64 age-matched healthy volunteers, 44 patients with endogenous depression, and 21 patients with schizophrenia. A significant negative correlation between delta TSH and age was found both in healthy subjects and in depressed patients. We based our comparison on normal ranges for delta TSH calculated from the delta TSH values in the healthy subjects related to age. It was then seen that blunted TSH response to TRH does not occur significantly more often in depression (13.6%) than in healthy controls (4.7%). Blunted TRH test results were also found in a considerable number of severely ill schizophrenic patients (19%). Application of an improved radioimmunoassay revealed a highly significant correlation between TSH values at baseline and after stimulation, and showed decreased baseline TSH levels in subjects with blunted TRH test results.

The TRH stimulation test and reverse T3 in depression

Blunted TSH response to TRH and elevation of reverse T3 (rT3) have been reported in depression, though the relationship between these two abnormalities has not been clear. The authors measured basal levels of T4, T3, rT3 and the TSH response to TRH in a group of 28 depressed men and women, unipolar and bipolar subtypes. No significant difference was found between these two subtypes of depression with respect to mean basal hormonal levels or magnitude of the TSH response to TRH. Two males had slight, but significant elevations of rT3 though only one of them had a blunted TSH response to TRH levels and the TSH response to TRH. Finally no significant correlation was found between rT3 levels and the TSH response to TRH.

Dexamethasone suppression, protirelin stimulation, and insulin infusion in subtypes of recovered depressive patients

Twenty-eight patients (10 bipolar, 13 depressive spectrum disease, and 5 familial pure depressive), recovered from depression for an average of 1 year, underwent a series of basal and provocative endocrine tests. No significant differences were found among depressive subtypes in thyrotropin, cortisol, or growth hormone measurements either before or after provocative testing with the exception of growth hormone response to insulin-induced hypoglycemia. Patients with depressive spectrum disease showed a significantly different growth hormone response to insulin-induced hypoglycemia than patients with bipolar disorder, a finding which suggests differences in alpha-adrenergic receptor sensitivity between these groups.