Thyroid function and metabolic state in chronic renal failure

Evaluation of Thyroid Function in Patients Treated with Continuous Ambulatory Peritoneal Dialysis (CAPD)

Abnormal thyroid function has been described in chronic renal insufficiency, and further changes occur with increasing time on hemodialysis. This study on two groups of patients was done to determine whether treatment with CAPD induces changes in thyroid function. Group A included 16 patients with an average duration of treatment of 2.1 ± 1.1 months; group B included 12 patients with 8.1 ± 2 months. We measured total T4 and T3, free T4, TBG, RT3U, FTI, T4/T3 and basal TSH, and TSH induced by TRH stimulation in plasma, and total and free T4 in dialysate. The results showed a significant decrease in total T4 and T3 in plasma, but no change in free T4 or TSH and no appreciable amounts of the hormones in the dialysate. We believe the decrease in total T4 and T3 is secondary to alterations in transport proteins while thyroid function is maintained by normal free T4 and TSH levels more dependable parameters for the interpretation of thyroid function in chronic diseases.

Thyroid disease in end-stage renal disease

PURPOSE OF REVIEW

Hypothyroidism is a highly prevalent endocrine disorder in the end-stage renal disease (ESRD) population, yet many cases may remain latent and undiagnosed.

RECENT FINDINGS

Epidemiologic data show that there is a nearly five-fold higher prevalence of hypothyroidism in advanced chronic kidney disease (CKD) patients vs. those without CKD. Given that the metabolism, degradation, and excretion of thyroid hormone and its metabolites, as well as the regulation of the hypothalamic-pituitary-thyroid axis may be altered in ESRD, certain considerations should be made when interpreting thyroid functional tests in these patients. Growing evidence shows that hypothyroidism and other thyroid functional test derangements are associated with higher risk of cardiovascular disease, worse patient-centered outcomes, and survival in the advanced CKD population, including those with ESRD. Although limited data examining treatment of hypothyroidism suggests benefit, further studies of the efficacy and safety of thyroid hormone supplementation, including clinical trials and rigorous longitudinal observational studies are needed to inform the management of thyroid dysfunction in CKD.

SUMMARY

Given the high burden of hypothyroidism in ESRD patients, and potential ill effects on their cardiovascular health, patient-centered outcomes, and survival, further research is needed to inform the optimal management of thyroid dysfunction in this population.

Thyroidal Status in Uremia - Effects of Hemodialysis and CAPD

Thyroid function was explored in 27 CAPD patients and 25 HD patients. Dialysis was associated with low T3 and T4 levels, increased rT3 concentrations, normal T4: T3 and reduced T4: rT3 ratios, normal FT3 and Thyroglobulin concentrations. TSH levels increased during dialysis but still fell within normal limits. The data rule out a condition of primary hypothyroidism and point out to increased thyroidal dismission associated with the block T4-T3 in peripheral cells. Also the increased FT4 levels in CAPD patients could be due to de novo dismission of thyroidal T4.

TSH Response to TRH in Hemodialysis and CAPD Patients

The thyroid status was studied in 19 uremic patients (11 on HD and 8 on CAPD) and in a group of 17 healthy adult patients. In uremic patients T3 and T4 were significantly reduced (p < 0.001) and rT3 was increased (p < 0.001). The time course TSH response to TRH showed a lower peak response (in 5 patients it did not exceed 5 μU/ml) which on turn was also delayed (the peak was observed at 60 minutes in 63% of them). TSH concentrations in uremics were increased at 0 time (p < 0.02), lower at 20 minutes (p < 0.01) and increased at 120 minutes (p < 0.02). No difference existed between HD and CAPD. The thyroid response to TSH was normal as showed by a normal percent increase over basal values of T3 concentrations at 120 minutes. Uremic patients also showed a peak GH response at 20 minutes which was not observed in controls. The data exclude the existence on a primary form of hypothyroidism and point to the existence of hypothalamic-pituitary abnormalities, which should not be taken as indicative of secondary and/or tertiary hypothyroidism since FT4 values were normal in HD and increased in patients undergoing CAPD (p < 0.05) who on turn showed lower plasma albumin concentrations (p < 0.05).

Evaluation of oxidative stress and thyroid hormone status in hemodialysis patients in Gorgan

AIMS

The aim of this study focused on serum malondialdehyde (MDA) levels and erythrocyte superoxide dismutase (SOD) and catalase (CAT) activities in hemodialysis patients and compared with control groups.

MATERIALS AND METHODS

Forty-five hemodialyzed patients and 45 control groups recruited in this study. Serum creatinine and urea, thyroid hormones (THs) levels and erythrocyte antioxidant enzyme activities were determined.

RESULTS

Hemodialysis (HD) patients showed higher levels of MDA than control groups (P < 0.01), but the levels of thyroxin (T3), free triiodothyronine (fT3), and free thyroxin (fT4), SOD and CAT were low in HD patients (P < 0.01). Serum T3, fT3, and fT4 levels were significantly negative correlated with MDA (P < 0.01).

CONCLUSION

It is concluded that serum lipid peroxidation is markedly increased in HD patients. This means that elevated reactive oxygen species may interact with the lipid molecules in HD patients. HD may cause significant changes in TH levels. Thyroid-stimulating hormone level in HD patients is slightly similar to that of control groups. This suggests that thyroid is able to resynthesize for hormonal urinary losses.

Thyroid functional disease: an under-recognized cardiovascular risk factor in kidney disease patients

Thyroid functional disease, and in particular hypothyroidism, is highly prevalent among chronic kidney disease (CKD) and end-stage renal disease (ESRD) patients. In the general population, hypothyroidism is associated with impaired cardiac contractility, endothelial dysfunction, atherosclerosis and possibly higher cardiovascular mortality. It has been hypothesized that hypothyroidism is an under-recognized, modifiable risk factor for the enormous burden of cardiovascular disease and death in CKD and ESRD, but this has been difficult to test due to the challenge of accurate thyroid functional assessment in uremia. Low thyroid hormone levels (i.e. triiodothyronine) have been associated with adverse cardiovascular sequelae in CKD and ESRD patients, but these metrics are confounded by malnutrition, inflammation and comorbid states, and hence may signify nonthyroidal illness (i.e. thyroid functional test derangements associated with underlying ill health in the absence of thyroid pathology). Thyrotropin is considered a sensitive and specific thyroid function measure that may more accurately classify hypothyroidism, but few studies have examined the clinical significance of thyrotropin-defined hypothyroidism in CKD and ESRD. Of even greater uncertainty are the risks and benefits of thyroid hormone replacement, which bear a narrow therapeutic-to-toxic window and are frequently prescribed to CKD and ESRD patients. In this review, we discuss mechanisms by which hypothyroidism adversely affects cardiovascular health; examine the prognostic implications of hypothyroidism, thyroid hormone alterations and exogenous thyroid hormone replacement in CKD and ESRD; and identify areas of uncertainty related to the interplay between hypothyroidism, cardiovascular disease and kidney disease requiring further investigation.

Importance of specific reference values for evaluation of the deteriorating thyroid function in patients with end-stage renal disease on hemodialysis

BACKGROUND/AIM

We evaluated the thyroid function in end-stage renal disease (ESRD) on maintenance hemodialysis.

MATERIAL/METHODS

Thyroid function and clinical hypothyroid score were evaluated in 145 ESRD patients.

RESULTS

Comparison of thyroid function between 127 ESRD patients, excluding 18 patients with suppressed or elevated serum TSH level, and age/sex-matched healthy controls (76 in midlife group aged under 65 and 51 in late-life group aged 65 or over) using a multivariate logistic regression analysis suggested significant difference (P < 0.0001), mainly in serum fT4 level (P = 0.0099) and age (P = 0.0492), but not in serum fT3 (not significant; ns), TSH (ns) level or fT3/fT4 ratio (ns). Serum fT3 level and fT3/fT4 ratio were significantly lower (P < 0.001) in late-life group only in ESRD. Reference values calculated for midlife ESRD patients, such as 0.6-1.3 ng/dl for fT4 compared with 0.8-1.7 ng/dl for healthy control, were helpful for the diagnosis of mild but definite hyperthyroidism in whom serum fT4 level was 1.5 ng/dl. The prevalence of primary thyroid dysfunction, compared with the values for ESRD, was 0.7 % for hyperthyroidism, 1.4 % for overt hypothyroidism and 10.3 % for subclinical hypothyroidism. Hypothyroid score was high among those with ESRD independent of thyroid dysfunction.

CONCLUSIONS

Serum fT4 level was markedly lower without a change in fT3/fT4 ratio in ESRD. This may suggest typical carbohydrate-sufficient non-thyroidal illness. The specific reference values for ESRD were useful to evaluate borderline thyroid dysfunction and to evaluate the prevalence of the patients with primary thyroid dysfunction in ESRD.

Prevalence and clinical characteristics of hypothyroidism in a population undergoing maintenance hemodialysis

BACKGROUND

The prevalence of hypothyroidism in persons with chronic kidney disease is documented to be higher, compared to the normal population. However, no data is available about the prevalence rate of hypothyroidism among hemodialysis patients in Nepal.

METHODS

A cross-sectional analysis was done on consecutive patients enrolled for maintenance hemodialysis in the Hemodialysis Unit of Gandaki Medical College Teaching Hospital, Pokhara, Nepal, during the period of one year (1(st) January 2011 to 31(st) December 2011). Total 64 subjects with end stage renal disease were recruited for the study. Thyroid function tests were performed at the time of starting regular hemodialysis. Classical symptoms and signs of hypothyroidism were assessed in all patients.

RESULTS

Among the study subjects 17 (26.6%) had serum thyroid stimulating hormone levels above the laboratory reference range (>6.16 μIU/ml). Among them 12 (18.7%) patients had clinically significant symptoms or signs requiring thyroxin replacement. Cold intolerance, constipation, tingling sensation, dry skin, periorbital odema, pericardial effusion, pleural effusion and ascites were found at significantly higher rate in the hypothyroid patient group (p<0.05).

CONCLUSION

The diagnosis of hypothyroidism can be easily missed in the end-stage kidney disease population, because the symptoms of chronic kidney disease and hypothyroidism overlap. In our study we have found high prevalence of hypothyroidism. Clinicians should pay attention on this factor and screen routinely for thyroid disorders in the chronic kidney disease population.

Thyrotropin isoforms: implications for thyrotropin analysis and clinical practice

Serum thyrotropin (TSH) is considered the single most sensitive and specific measure of thyroid function in the general population owing to its negative logarithmic association with free triiodothyronine and free thyroxine concentrations. It is therefore often the test of choice for screening, diagnosis, and monitoring of primary hypothyroidism. Serum TSH concentrations can be analyzed quantitatively using third-generation immunoassays, whereas its bioactivity can be measured by TSH activity assays in cell culture. Theoretically, if serum TSH concentrations are directly related to TSH activity, the two tests should yield comparable results. However, on occasion, the results are discordant, with serum concentrations being higher than TSH biological activity. This review focuses on the dissociation between the clinical state and serum TSH concentrations and addresses clinically important aspects of TSH analysis.

Hypothyroidism and mortality among dialysis patients

BACKGROUND AND OBJECTIVES

Hypothyroidism is highly prevalent among ESRD patients, but its clinical significance and the benefits of thyroid hormone replacement in this context remain unclear.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

This study examined the association between hypothyroidism and all-cause mortality among 2715 adult dialysis patients with baseline thyrotropin levels measured between April of 2005 and April of 2011. Mortality was ascertained from Social Security Death Master Index and local registration systems. The association between hypothyroidism (thyrotropin greater than assay upper limit normal) and mortality was estimated using Cox proportional hazards models. To reduce the risk of observing reverse-causal associations, models included a 30-day lag between thyrotropin measurement and at-risk time.

RESULTS

Among 350 (12.9%) hypothyroid and 2365 (87.1%) euthyroid (assay within referent range) patients, 917 deaths were observed during 5352 patient-years of at-risk time. Hypothyroidism was associated with higher mortality. Compared with thyrotropin in the low-normal range (0.4-2.9 mIU/L), subclinical hypothyroidism (thyrotropin >upper limit normal and ≤10.0 mIU/L) was associated with higher mortality; high-normal thyrotropin (≥3.0 mIU/L and ≤upper limit normal) and overt hypothyroidism (thyrotropin >10.0 mIU/L) were associated with numerically greater risk, but estimates were not statistically significant. Compared with spontaneously euthyroid controls, patients who were euthyroid while on exogenous thyroid replacement were not at higher mortality risk, whereas patients who were hypothyroid were at higher mortality risk. Sensitivity analyses indicated that effects on cardiovascular risk factors may mediate the observed association between hypothyroidism and death.

CONCLUSIONS

These data suggest that hypothyroidism is associated with higher mortality in dialysis patients, which may be ameliorated by thyroid hormone replacement therapy.

Microbicidal efficacy of povidone-iodine in a noncontact manner applied to a continuous ambulatory peritoneal dialysis connection system

In peritoneal dialysis (PD) the dialysate is introduced into the peritoneal cavity, and the peritoneal membrane is used as the dialysis membrane. In PD, patients exchange the dialysate by themselves through the connection tube attached to the indwelling catheter that is inserted into the peritoneal cavity. Microbes may enter the peritoneal cavity during dialysate exchange, and, therefore, peritonitis is a potential complication of PD. To prevent microbial contamination, the connection tube tip is generally sealed with a protection cap containing povidone-iodine (PVP-I) during the dwelling time. This cap is designed to make direct contact with the tube tip so that microbes attached during dialysate exchange are killed by the next dialysate exchange. However, if excess PVP-I flows into the peritoneal cavity and is absorbed into the body, the complications, including thyroid dysfunction, peritoneal inflammation, and fibrous thickening, can develop. Therefore, in this study, a new manual connection system (Zero System, JMS Co., Ltd., Hiroshima, Japan) for continuous ambulatory peritoneal dialysis was investigated to confirm that the PVP-I solution within the protection cap of the new system would not flow into the fluid passing through the tube. An experiment was also performed to confirm that the microbes on the connector tip become completely nonviable after attachment of the cap for 3 hours. The cap is fitted with a sponge containing a 10% PVP-I solution, the same as for the conventional cap system. However, the system is designed to achieve disinfection without contact, unlike with the conventional system, in which disinfection is achieved by direct contact of the PVP-I-containing sponge with the open end of the attached connector. The test results demonstrated that adequate disinfection with this system can be achieved by the next exchange, while avoiding entry of PVP-I into the peritoneal cavity from the cap. The results suggest that the use of this connection system can avoid adverse reactions arising from the absorption of PVP-I and prevent the onset of peritonitis caused by microbial invasion of the peritoneal cavity.

Thyroid Hormone Transport is Disturbed in Erythrocytes from Patients with Chronic Renal Failure on Hemodialysis

AIMS

To now, there are no studies reporting whether thyroid hormones (THs) transport play a role in thyroid hormone dysfunction observed in chronic renal failure (CRF). Therefore, the aim of this study was to investigate the transport of THs in erythrocytes from patients with CRF on hemodialysis (HD).

METHODS

[125I]-L-triiodothyronine ([125I]T3) and [125I]-L-thyroxine ([125I]T4) erythrocytes uptake was measured at 1 min and 5 min. To study L-triiodothyronine (LT3) and L-thyroxine (LT4) efflux from erythrocytes, we preloaded the cells during 180 min with [125I]T3 or [125I]T4 and measured their [125I]T3 or [125I]T4 efflux during 60 min.

RESULTS

[125I]T3 uptake in erythrocytes from uremic patients pre-HD was higher than control subjects by 50% at 1 min and by 55% at 5 min. However, [125I]T4 uptake in erythrocytes from uremic patients was significantly lower at 1min (88%) and at 5 min (63%). LT3 efflux rate was lower and LT4 efflux was significantly higher than in control subjects. After 60-min of efflux, LT3 remained in erythrocytes was 80% higher and LT4 was 57% lower than in normal individuals. Neither [125I]T3 and [125I]T4 uptake, nor efflux rates were changed by hemodialysis.

CONCLUSION

Despite the fact that uremic patients on hemodialysis show low serum levels of LT3, changes in LT3 influx and efflux could act as a compensatory mechanism that neutralize thyroid hormone dysfunction in order to maintain the euthyroid state.

Low triiodothyronine and survival in end-stage renal disease

Plasma triiodothyronine (fT3) is a strong predictor of adverse clinical outcomes in various clinical conditions. Since fT3 in patients with end-stage renal diseases (ESRD) is frequently reduced and is associated with inflammation and cardiovascular damage, we prospectively tested the hypothesis that it predicts death in a cohort of 200 hemodialysis patients. Plasma fT3 was lower in ESRD patients (P<0.001) than in healthy subjects and in clinically euthyroid patients with normal renal function. During the follow-up 102 patients died. Patients who died had significantly lower plasma fT3 than those who survived (P<0.001) and in a Kaplan-Meyer analysis plasma fT3 was associated with death (P<0.001). On multivariate Cox's regression analyses, adjusting for a series of traditional and emerging risk factors including inflammation markers, patients with relatively higher plasma fT3 (hazard ratio (HR) (1 pg/ml increase in fT3)) had a 50% reduction in the risk of death (HR=0.50, 95% CI: 0.35-0.72) as compared to those having relatively lower fT3 levels. Of note, plasma fT3 captured most of the predictive power of interleukin-6 (IL-6) because this latter variable emerged as a significant predictor of death only in a model excluding fT3. Low fT3 is an independent predictor of death in hemodialysis patients. These data lend support to the hypothesis that thyroid dysfunction is implicated in the high risk of the ESRD population.

Thyroid hormone receptor binding to DNA and T3-dependent transcriptional activation are inhibited by uremic toxins

Background

There is a substantial clinical overlap between chronic renal failure (CRF) and hypothyroidism, suggesting the presence of hypothyroidism in uremic patients. Although CRF patients have low T₃ and T₄ levels with normal thyroid-stimulating hormone (TSH), they show a higher prevalence of goiter and evidence for blunted tissue responsiveness to T₃ action. However, there are no studies examining whether thyroid hormone receptors (TRs) play a role in thyroid hormone dysfunction in CRF patients. To evaluate the effects of an uremic environment on TR function, we investigated the effect of uremic plasma on TRβ1 binding to DNA as heterodimers with the retinoid X receptor alpha (RXRα) and on T₃-dependent transcriptional activity.

Results

We demonstrated that uremic plasma collected prior to hemodialysis (Pre-HD) significantly reduced TRβ1-RXRα binding to DNA. Such inhibition was also observed with a vitamin D receptor (VDR) but not with a peroxisome proliferator-activated receptor gamma (PPARγ). A cell-based assay confirmed this effect where uremic pre-HD ultrafiltrate inhibited the transcriptional activation induced by T₃ in U937 cells. In both cases, the inhibitory effects were reversed when the uremic plasma and the uremic ultrafiltrate were collected and used after hemodialysis (Post-HD).

Conclusion

These results suggest that dialyzable toxins in uremic plasma selectively block the binding of TRβ1-RXRα to DNA and impair T₃ transcriptional activity. These findings may explain some features of hypothyroidism and thyroid hormone resistance observed in CRF patients.

Nonthyroidal illness syndrome or euthyroid sick syndrome?

OBJECTIVE

To characterize the nonthyroidal illness syndrome (NTIS) and to discuss various underlying potential biochemical mechanisms for this condition.

METHODS

The pertinent medical literature was reviewed, and studies of thyroid function in systemic non-thyroidal illnesses were summarized.

RESULTS

Abnormalities of thyroid function in the NTIS have been classified into four major categories: (1) low triiodothyronine (T3) syndrome, (2) a combination of low T3 and low thyroxine (T4), (3) high T4 syndrome, and (4) other abnormalities. The NTIS has been noted in essentially all severe systemic illnesses and after caloric deprivation, major operations, and administration of some drugs. Some mechanisms that may contribute to low serum T3 in the NTIS are decreased type I 5 -monodeiodinase in tissues, decreased uptake of T4 by tissues, decreased serum binding, increased reverse T3, alterations in selenium status, cytokines, and a decrease in thyrotropin. Decreased thyrotropin may also contribute to low T4 levels in NTIS, as may decreased serum T4-binding proteins, abnormalities in T4-binding globulin, and circulating inhibitors of binding of T4 to serum proteins. Although T4 treatment of patients with NTIS has yielded little improvement, administration of T3 has produced some beneficial effects.

CONCLUSION

Further studies should be conducted to determine appropriate patient populations, dose-response ratios, and possible adverse effects of treatment of the NTIS with T3.

The controversy of the treatment of critically ill patients with thyroid hormone

There is currently a vast literature available on the changes in thyroid function tests that occur during non-thyroidal illness. The aetiology of these changes is, however, controversial, especially with respect to whether they play an adaptive role for the organism in order to cope with stress or whether they represent primary pathology of the pituitary-thyroid axis. This is particularly true for critically ill patients, in whom the most significant changes in thyroid function are observed. The changes include low levels of thyroxine and very low levels of tri-iodothyronine, which would, on the surface, appear to indicate hypothyroidism. Therapy with thyroid hormone, as either L-T4 or L-T3, has therefore been suggested because of these low values for thyroid hormones in the blood. It is, however, unclear whether treating these patients with thyroid hormone is beneficial or harmful. Multiple studies have addressed this issue with patients with cardiac disease, sepsis, pulmonary disease (e.g. acute respiratory distress syndrome) or severe infection, or with burn and trauma patients. In spite of a very large number of published studies, it is very difficult to form clear recommendations for treatment with thyroid hormone in the intensive care unit. Instead, we find the evidence far from compelling, and would advise withholding thyroid hormone therapy in the critical care setting in the absence of clear clinical or laboratory evidence for hypothyroidism.

Low free thyroxine concentrations and deficient nocturnal surge of thyroid-stimulating hormone in haemodialysed patients compared with undialysed patients

BACKGROUND

There is little information on the differences in pituitary-thyroid function between undialysed and haemodialysed patients.

METHODS

Serum concentrations of free thyroxine (T(4)) and free triiodothyronine (T(3)), measured by enhanced chemiluminescence immunoassay, and thyroid-stimulating hormone (TSH) were compared in undialysed (n=22) and haemodialysed patients (n=85). The response of the serum TSH concentration to exogenously administered thyrotropin-releasing hormone (TRH) and circadian variation in serum TSH were also studied in the two groups.

RESULTS

Serum free T(4) concentration was significantly lower in haemodialysed than in undialysed patients (1.02+/-0.02 vs 1.33+/-0.06 ng/dl, P<0.0001). Serum concentrations of free T(3) and TSH were essentially the same for the two groups. The response of serum TSH concentration to TRH was basically the same. Serum TSH concentration in undialysed patients during the night and in the morning were 142.4+/-15.4% and 121.7+/-4.1% of that during the day, the differences being significantly different. A nocturnal surge of TSH was not observed in haemodialysed patients.

CONCLUSIONS

Low serum free T(4) concentration and a deficient nocturnal surge of TSH were found in haemodialysed patients compared with undialysed patients. The deficient nocturnal surge of TSH may contribute to the lower serum free T(4) concentration in haemodialysed patients.

Serum substances that interfere with thyroid hormone assays in patients with chronic renal failure

OBJECTIVE

Serum thyroid hormone concentrations in patients with chronic renal failure are usually low, despite normal serum TSH levels. We investigated the effect on thyroid hormone assays of serum dialysable organic acids that are elevated in uraemic patients.

PATIENTS

Serum samples from 42 patients with chronic renal failure who were receiving haemodialysis and 37 sex- and age-matched healthy subjects were examined.

DESIGN AND MEASUREMENTS

Serum thyroid hormone concentrations were measured with an analogue radioimmunoassay (RIA), a labelled antibody assay, and an equilibrium dialysis/RIA method. Serum concentrations of organic acids were determined with high performance liquid chromatography.

RESULTS

Serum thyroid hormone levels determined by an analogue RIA and a labelled antibody assay in uraemic patients increased, and serum concentrations of organic acids decreased following haemodialysis. A significant association existed between serum free T3 (FT3) levels determined by an analogue RIA and serum concentrations of indoxyl sulphate (IS) prior to dialysis. There was also a significant association between serum free T4 (FT4) levels determined by an analogue RIA and serum concentration of IS and hippuric acid (HA) prior to dialysis. There was a significant association between the changes of serum concentrations of indole acetic acid (IAA) and FT4 concentrations prior to and following haemodialysis when determined by an analogue RIA. Serum FT3 and FT4 levels significantly decreased after the addition of IS to serum from healthy subjects when determined by an analogue RIA but not by a labelled antibody assay. Serum FT4 levels, but not FT3 levels, decreased after addition of IAA when determined by an analogue RIA. Serum FT4 concentrations determined by an equilibrium dialysis/RIA were significantly higher than those determined by the other two methods. The addition of IS, IAA, and HA to serum samples from healthy subjects significantly increased FT4 concentrations when determined by an equilibrium dialysis/RIA method.

CONCLUSIONS

Increased serum levels of indoxyl sulphate, indole acetic acid and hippuric acid in sera of uraemic patients may interfere with thyroid hormone measurements when an analogue radioimmunoassay is used. In contrast, there was little Interference with a labelled antibody assay. Dialysable organic acids may also interfere with thyroid hormone assays determined by an equilibrium dialysis/radioimmunoassay method.

Thyroid function and serum thyroid binding proteins in prepubertal and pubertal children with chronic renal insufficiency receiving conservative treatment, undergoing hemodialysis, or receiving care after renal transplantation

OBJECTIVE

The abnormalities reported in some thyroid function tests in children with renal disease could be adaptive phenomena, shared by a variety of other nonthyroidal illnesses, or could reflect hypothyroidism.

STUDY DESIGN

To answer this question, we studied thyroid function and serum thyroid binding proteins in 36 prepubertal and 23 pubertal patients with renal disease receiving three different therapies: conservative treatment, hemodialysis, and care after renal transplantation.

RESULTS

During prepuberty, the serum concentration thyroxine binding globulin (mean +/- SE) in the three groups of patients (294 +/- 18, 303 +/- 18, and 323 +/- 16 nmol/L, respectively) was significantly lower than in prepubertal control subjects (451 +/- 71 nmol/L). Only in prepubertal patients after renal transplantation (3583 +/- 573 nmol/L) were serum thyroxine binding prealbumin values lower than in respective control subjects (5999 +/- 908 nmol/L). The serum total thyroxine concentration in the three groups of patients (108 +/- 41.9, 121 +/- 5.7, and 123 +/- 5.5 nmol/L, respectively) was significantly lower than in prepubertal control subjects (149 +/- 10 nmol/L), whereas serum free thyroxine and serum albumin-bound thyroxine concentrations were similar to those in control subjects. The serum total triiodothyronine level in the three groups of patients (2.29 +/- 0.82, 2.13 +/- 0.13, and 2.01 +/- 0.20 nmol/L respectively) was significantly lower than in prepubertal control subjects (3.04 +/- 0.24 nmol/L), whereas serum levels of free triiodothyronine and serum albumin-bound triiodothyronine were similar to those in prepubertal control subjects. During puberty, serum thyroxine binding globulin and serum thyroxine binding prealbumin levels in the three groups of patients were not statistically different from those in pubertal control subjects (309 +/- 47 and 4950 +/- 1230 nmol/L, respectively). Serum levels of total thyroxine, free thyroxine, albumin-bound thyroxine, total triiodothyronine, free triiodothyronine, and albumin-bound triiodothyronine were similar to those in pubertal control subjects except for pubertal patients undergoing hemodialysis. In all clinical groups the basal serum thyrotropin concentration was similar to those in respective control subjects. The frequency of goiter was increased in patients undergoing hemodialysis, probably as a result of iodide washout with dialysis.

CONCLUSION

Children and adolescents with chronic renal insufficiency or endstage renal disease or after renal transplantation do not have a primary abnormality of thyroid function and therefore are not candidates for thyroid hormone treatment.

Reduced tissue thyroid hormone levels in fatal illness

Patients with severe nonthyroidal illnesses (NTIs) frequently have decreased serum concentrations of triiodothyronine (T3) and less often of thyroxine (T4) without clear evidence of hypothyroidism. To determine whether T3 and T4 levels are also reduced in the tissues, we analyzed autopsy samples from 12 patients dying of NTI and 10 previously healthy individuals dying suddenly from trauma. Mean serum T3, T4, and free T4 index values were lower by 79%, 71%, and 49%, respectively, in the NTI group than in controls, but serum thyrotropin (TSH) values did not differ significantly. Mean T3 concentrations in cerebral cortex, hypothalamus, pituitary, liver, kidney, and lung were lower in the NTI group than in controls by 43% to 76%, but mean values in heart and skeletal muscle did not differ significantly between the groups. The mean liver T4 concentration was 66% lower in the NTI group, but mean T4 concentrations in the cerebral cortex were similar in the two groups. These results indicate that many tissues may be deficient in thyroid hormones in patients with fatal NTI, although the severity of the reduction in thyroid hormone concentrations may vary from one organ to another.

The hepatocellular thyroid status of uremic rats estimated from the abundances of thyroid hormone-dependent nucleoplasmic proteins

Although the serum thyroxine (T4) and triiodothyronine (T3) concentrations of uremic rats are commensurate with moderate hypothyroidism, their thyroid status at the tissue level remains controversial. To help establish the hepatocellular thyroid status of uremic rats, a novel tissue marker (nuclear protein abundances) was evaluated in uremic rats (U), hypothyroid rats (H), and hypothyroid uremic rats (HU). Uremia was established by five-sixths nephrectomy. Moderate hypothyroidism was established by partial thyroidectomy or by provision of drinking water supplemented with propylthiouracil and T4. Normal rats (N) and pair-fed, sham-operated rats (1 to 3 weeks after surgery) served as controls. Animals were killed 1 to 5 weeks postoperatively. The following values were obtained 5 weeks after surgery, at which time the total and free serum T4 and T3 levels of the hypothyroid rats (H) were equivalent to those of the uremic rats (U). Total T4 (micrograms/dL +/- 1 SD): N, 5.4 +/- 1.7; H, 2.2 +/- 0.5; U, 1.9 +/- 1.5; HU, 0.5 +/- 0.0. Free T4 (ng/dL +/- 1 SD): N, 535 +/- 165; H, 126 +/- 37; U, 135 +/- 89; HU, 26 +/- 1. Total T3 (ng/dL +/- 1 SD): N, 63 +/- 20; H, 39 +/- 14; U, 38 +/- 18; HU, 13 +/- 4. Free T3 (ng/dL +/- 1 SD): N, 7.83 +/- 3.00; H, 3.87 +/- 1.05; U, 3.47 +/- 1.73; HU, 0.94 +/- 0.47. Hepatocellular thyroid status was estimated from the relative abundances of two nucleoplasmic proteins on polyacrylamide gel electrophoregrams.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of chronic peritoneal dialysis on thyroid function tests

Peritoneal dialysis is associated with large losses of protein. In order to quantify thyroid hormone excretion in the dialysate and to examine the possibility that peritoneal dialysis may result in clinical hypothyroidism, nine endstage renal disease (ESRD) patients undergoing either continuous ambulatory peritoneal dialysis (CAPD) or chronic intermittent peritoneal dialysis (IPD) were studied. Total protein excretion in the peritoneal fluid was 21.5 +/- 2.1 g/24 h and did not vary with the mode of peritoneal dialysis. Thyroid binding globulin (TBG) excretion was 6.4 +/- 1.3 mg/24 h, higher than the values reported in the literature for urinary TBG excretion in patients with the nephrotic syndrome. Despite the higher TBG losses, serum TBG remained in the normal range. Mean peritoneal total T4 and T3 were 8.1 +/- 1.6 micrograms/24 h and 89.5 +/- 14.6 ng/24 h, and there was a significant correlation between peritoneal T4 and TBG (r = 0.69; P less than 0.01) and between peritoneal total proteins and T4 (r = 0.80; P less than 0.001). Despite the finding that large amounts of protein are lost in peritoneal fluid, T4 and T3 losses were relatively modest and remained below their daily production rates, and none of the patients were overtly hypothyroid. Serum thyroid stimulating hormone (TSH) was mildly elevated in three of nine patients and was consistent with early thyroid failure. The patients' serum iodine levels were higher than normal but did not predict the patients' thyroid status. We conclude that major protein losses could predispose patients undergoing CAPD to thyroid failure and that long-term follow-up of thyroid function is warranted in these patients.

Thyroid hormone indices in adult healthy subjects: no influence of aging

Controversy exists regarding the influence of aging on thyroid hormone metabolism. Several investigators report lowering of T3 and/or a rise in reverse T3 (rT3) in elderly subjects. Others suggest that these thyroid hormone alterations were secondary to associated disorders rather than old age, and questioned the "healthy" status of the subjects studied in the earlier reports. Therefore, to assess the possible effect of aging we studied T3 resin uptake, T4, free T4, T3, and rT3 concentrations in 152 euthyroid healthy adult subjects. These subjects were selected carefully and were therefore devoid of any illness, acute or chronic, and were not treated with any medications at the time of study. No significant alterations were noted in any of the thyroid hormone concentrations in subjects divided into groups according to age. Nor was there a significant difference in these parameters between men and women of any individual age group or for all ages combined. Therefore, old age per se may not influence thyroid hormone metabolism and hence may not induce changes in serum thyroid hormone concentrations. The changes in thyroid hormones noted previously in elderly subjects may be a reflection of concurrent disorders and not old age.

Blunted peripheral tissue responsiveness to thyroid hormone in uremic patients

To understand the biologic significance of the low triiodothyronine (T3) syndrome in patients with chronic renal failure (CRF), we examined thyroid hormone profile, basal O2 uptake (VO2), and peripheral blood mononuclear leukocyte (PBL) ouabain binding in these patients and in the control subjects before and after L-triiodothyronine (T3) and sodium ipodate treatment. In the controls (N = 8), T3 administration increased serum total T3 from 136 +/- 15 to 232 +/- 11 ng/dl, and reduced total thyroxine (T4) from 8.14 +/- 0.56 to 6.08 +/- 0.43 micrograms/dl, free T4 from 1.59 +/- 0.12 to 1.03 +/- 0.05 ng/dl and thyroid-stimulating hormone (TSH) from 1.74 +/- 0.24 to 0.41 +/- 0.09 microU/ml. VO2 increased from 2.66 +/- 0.11 to 3.15 +/- 0.09 ml/kg/min. Ipodate treatment, on the other hand, resulted in a reduction of serum total T3 to 102 +/- 21 ng/dl, an increase in total T4 to 9.59 +/- 0.50 micrograms/dl, free T4 to 1.91 +/- 0.13 ng/dl and TSH to 3.64 +/- 1.14 microU/ml. VO2 decreased to 2.43 +/- 0.06 ml/kg/min. P values ranged from less than 0.05 to less than 0.001. In the CRF patients (N = 14), T3 treatment also resulted in a rise in serum total T3 from 75 +/- 5 to 185 +/- 8 ng/dl. Total T4 declined from 6.68 +/- 0.34 to 5.18 +/- 0.48 micrograms/dl, free T4 from 0.85 +/- 0.1 to 0.67 +/- 0.08 ng/dl and TSH from 3.67 +/- 0.86 to 0.94 +/- 0.3 microU/ml. VO2, however, did not change (from 2.91 +/- 0.12 to 2.99 +/- 0.17 ml/kg/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Serum thyroglobulin in chronic renal failure--effects of haemodialysis

The influence of chronic renal failure (CRF) on serum thyroglobulin concentration (Tg) was investigated in 37 patients (29 on haemodialysis) and compared with results obtained from matched controls. Serum Tg did not differ significantly between CRF patients not on haemodialysis: median 24.1 micrograms/l, (range 2.5-47.0) and controls: median 23.6 micrograms/l, (range 2.1-53.0). Patients on haemodialysis had a significantly lower serum Tg level: median 11.4 micrograms/l (range 2.1-54.0) compared to controls (p less than 0.01) but no change in serum Tg level could be demonstrated after a single haemodialysis. A possible explanation for the low serum Tg level in patients with CRF on haemodialysis is decreased production parallelling the decreased production rate of T4 and T3. Since CRF patients not on haemodialysis had an unchanged serum Tg level compared to controls, haemodialysis was associated with small changes in serum Tg level, and since none of the patients had a serum Tg value above the upper reference limit we conclude that these changes were not of a magnitude likely to cause misinterpretation of results in routine clinical situations.

3,5-Diiodotyrosine and thyronine in the urine of patients with chronic renal disease

Urinary 3,5-diiodotyrosine (DIT) and thyronine (T0) excretion was investigated in 18 patients with chronic renal disease. In accord with previous findings serum T4 and thyroid hormone binding proteins measured in 17 patients were in the low or normal range. Urinary albumin excretion was elevated in all 18 and T4 binding prealbumin (TBPA) in 15 of the 18. Urinary T0 excretion measured in 12 patients was also significantly lower than normal (mean +/- SD 4.4 +/- 2.6 vs 15.8 +/- 5.8 nmol/24 h renal vs normal 2 P less than 0.001). In contrast urinary DIT excretion was significantly elevated in renal patients compared with normal subjects (2.0 +/- 1.5 vs 0.75 +/- 0.41 nmol/24 h, respectively). Possible sources of the increased DIT are discussed.

Adrenal insufficiency following unilateral adrenalectomy: a case report

We report a case of resection of a unilateral adrenal pseudocyst that precipitated life-threatening adrenal insufficiency. The patient had extremis unresponsive to pressor agents in the immediate postoperative period. Hydrocortisone administration produced temporary resolution and a cosyntropin-stimulation test confirmed adrenal insufficiency. Because of the presence of an adrenal mass, the preoperative evaluation included a formal endocrinological evaluation. Thus, we were able to document the occurrence of acute postoperative primary adrenal insufficiency.

Abnormalities of thyroid function tests in hospital inpatients

Results of thyroid function tests were analysed in 199 clinically euthyroid inpatients with normal serum thyroid stimulating hormone values. Serum total triiodothyronine was less than 1.25 nmol/l in 61.8% of samples, free triiodothyronine less than 3.9 pmol/l in 57.8%, total thyroxine less than 63 nmol/l in 21.1% and free thyroxine less than 9.5 pmol/l in 17.6%. In contrast, thyroxine binding globulin ratio was below normal (less than 5) in only 5 samples. A significant positive correlation (P less than 0.001) of serum free thyroxine with total thyroxine, thyroxine/thyroxine binding globulin ratio and free triiodothyronine was present as well as a significant negative correlation (P less than 0.001) with serum thyroid stimulating hormone. There was no correlation of free thyroxine measurements with serum albumin or non-esterified fatty acid concentrations. Although serum free thyroxine is low in a number of patients with non-thyroidal illnesses, this does not appear to be due to a rise in non-esterified fatty acids or a fall in albumin as has been proposed. Serum thyroid stimulating hormone measurements are essential to confirm the diagnosis of hypothyroidism in such subjects.

Protective adaptation of low serum triiodothyronine in patients with chronic renal failure

Low serum triiodothyronine (T3) concentration is frequently found in patients with chronic renal failure (CRF). To test the hypothesis that this may serve to minimize protein catabolism in these patients, we measured nitrogen balance (Nb) in seven CRF and four control subjects in the basal state and when serum T3 concentration was elevated by L-triiodothyronine (LT3) and suppressed by sodium ipodate administration. In the basal state, both the controls and the CRF patients were in positive Nb, 0.02 +/- 0.51 and 0.58 +/- 0.34 g/day, respectively. During LT3 administration, Nb decreased to -0.80 +/- 0.39 g/day in the CRF patients (P less than 0.01), but remained positive, 0.22 +/- 0.67 g/day, in the controls. There was a significant negative correlation between serum T3 concentration and Nb in the CRF patients (r = -0.63, P less than 0.005), but not in the controls. Furthermore, urea nitrogen generation rate, calculated from urea kinetics, increased from a baseline of 4.6 +/- 0.55 to 6.0 +/- 0.50 mg/min during LT3 administration in the CRF patients (P less than 0.01). Sodium ipodate, which significantly lowered serum T3 concentrations, had little effect on nitrogen metabolism in the controls and the CRF patients. These data support the concept that low serum T3 concentrations may confer a protective effect on CRF patients regarding protein-nitrogen conservation and provide a rationale for not correcting such deficiency.

A longitudinal evaluation of thyroid function in critically ill surgical patients

Thyroid hormone alterations (known as the "sick-euthyroid syndrome") are common following major surgery, but the time course for appearance and recovery from these alterations has not previously been longitudinally studied in a large group of surgical patients. The authors prospectively studied 59 patients undergoing major surgery (coronary artery bypass grafting, pneumonectomy, or subtotal colectomy). Compared with preoperative values, the mean serum T4, T3, free T3, and TSH concentrations decreased significantly (p less than 0.05) following surgery. Serum reverse T3 and T3 resin uptake index increased, while free T4 levels remained unchanged. These changes were seen within 6 hours of surgery and normalized by 1 week after surgery. Although the serum TSH response to TRH was normal before and after surgery in 56 of the 59 patients, the maximal TRH-induced increase in serum TSH and the integrated serum TSH response to TRH were suppressed in the early perioperative period. This postoperative TSH suppression correlated with elevated postoperative plasma dopamine concentrations (r = 0.57, p less than 0.05). Three patients with compensated primary hypothyroidism were detected in the study and represent the first documentation of serial thyroid hormone and TSH levels in hypothyroid patients undergoing major surgery. These patients had similar changes in thyroid hormone values compared with euthyroid patients. The serum TSH response to TRH was suppressed into the normal range in two of these patients on the day following surgery. The authors conclude that the sick-euthyroid syndrome occurs within a few hours of major surgery and remits with convalescence. Postoperative decreases in serum TSH may mask the diagnosis of hypothyroidism. Surgical consultants should be aware of these rapid postoperative changes so that thyroid function tests are properly interpreted in patients who have undergone major surgery.

Alteration of pituitary-thyroid function in patients with chronic renal failure treated by haemodialysis or continuous ambulatory peritoneal dialysis

Pituitary-thyroid function was investigated in 60 patients with chronic renal failure and 18 normal subjects. Serum triiodothyronine and free thyroxine levels were lower in patients treated by either haemodialysis or continuous ambulatory peritoneal dialysis compared with the normal subjects. Serum thyroxine and free thyroxine index were significantly lower in the haemodialysis-treated patients than in the normal subjects. There were no differences in serum thyroxine and free thyroxine index between the continuous ambulatory peritoneal dialysis-treated and normal groups. Serum thyrotrophin was not raised in any of the groups but the serum thyrotrophin response to thyrotrophin-releasing hormone was blunted in both groups of patients. Basal serum prolactin and growth hormone were raised in both groups of patients but there was no significant difference between them. This study confirmed that pituitary-thyroid function is abnormal in patients receiving haemodialysis and established that a similar pattern of abnormalities occurs in patients undergoing continuous ambulatory peritoneal dialysis.

Serum thyroid hormone changes during whole body hyperthermia

In order to elucidate changes in thyroid hormone metabolism during acute heat stress, we measured sequentially serum thyroxine (T4), triiothyronine (T3), and reverse T3 (rT3) levels in 5 patients with neoplasia during treatment with whole body hyperthermia. The core temperature was raised from 37.0 degrees C to 42.0 degrees C over a 2-hour period, maintained at 42.0 degrees C for 2 hours, and then cooled to 37.0 degrees C over 2 hours. This short period of severe hyperthermia produced a fivefold rise in rT3 and a fall in T3 levels to one half of baseline levels. T4 and free T4 levels increased slightly, but thyrotropin (measured in two patients) did not change. These changes in T3 and rT3 levels were detectable at the fourth hour after onset of hyperthermia, were maximal at 24 and 48 hours, and in one patient were uncorrected after 4 days. We conclude that this reciprocal change in T3 and rT3 levels is a response to stress and may represent in part adaptation to a high environmental temperature by the suppression of theromengic T3. Whole body hyperthermia of short duration for cancer therapy produces profound changes in the peripheral degradation of thyroxine, which last for several days. This must be considered in the management of patients receiving hyperthermia, and the technique itself may prove to be a useful model for the study of adaptation to heat stress.

Response of hepatic mitochondrial alpha-glycerophosphate dehydrogenase and malic enzyme to constant infusions of L-triiodothyronine in rats bearing the Walker 256 carcinoma. Evidence for divergent postreceptor regulation of the thyroid hormone response

To characterize the hepatic response to L-triiodothyronine (T3) in an experimental nonthyroidal disease, we determined the activity of hepatic mitochondrial alpha-glycerophosphate dehydrogenase (alpha-GPD) and cytosol malic enzyme (ME) as a function of the saturation of the nuclear T3 receptor during constant T3 infusions in rats bearing the Walker 256 carcinoma. Groups of control and tumor-bearing rats were infused by minipumps (Alza Corp., Palo Alto, CA) with vehicle, 1.2 or 4.5 micrograms T3/100 body wt per day for 3 d. The range for serum T3 was 47.2 +/- 4.1 to 165 +/- 17.3 ng/dl for the control rats and 13.2 +/- 1.3 to 135 +/- 14.3 ng/dl for the tumor-bearing rats. Nuclear T3 receptor concentration was between 0.41 +/- 0.06 and 0.47 +/- 0.02 ng/mg DNA in control rats and was decreased in tumor-bearing rats to between 0.23 +/- 0.03 and 0.26 +/- 0.03 ng/mg DNA. Nuclear T3 receptor concentrations were not influenced by the T3 infusions. Specifically bound nuclear T3, determined by radioimmunoassay of extracts of isolated nuclei, was decreased nearly 50% in the tumor-bearing rats. However, the calculated percentage saturation of the T3 nuclear receptor remained similar in control and tumor-bearing rats at each level of T3 infusion. Dose-response curves for alpha-GPD and ME were curvilinear and showed an exponential increase in enzyme activity with progressive receptor saturation. In tumor-bearing rats, the activity curves or calculated appearance rate curves for alpha-GPD were shifted significantly upward and to the left, indicating greater sensitivity to T3, and those of ME were shifted downward and to the right, indicating decreased responsiveness to T3. Our findings suggest that cellular factors result in postreceptor amplification of the alpha-GPD response and diminution of the ME response to T3 in tumor-bearing rats. Augmentation of the alpha-GPD response may be a prototype for other hormonal responses that enable the tumor-bearing rat to maintain an apparent euthyroid state in association with decreased serum T3.

Circulating thyroid hormones in progressive renal failure in the baboon (Papio ursinus)

In order to examine the effects of developing renal failure on circulating thyroid hormones, serum concentrations of thyroxine (T4), free T4 (FT4), triiodothyronine (T3) and reverse T3 (rT3) and TBG capacity were measured in 9 baboons before and during the progress of acute (mean survival 12 days), subacute (32 days) and chronic (120 days) renal failure following allogeneic renal transplantation. Irrespective of the rate of development of renal failure, there were significant, non linear (power functions) negative correlations between serum creatinine or urea concentrations and levels of T4, FT4 and T3; rT3 levels remained unchanged, but the T4: rT3 molar ratio fell from 236.5 +/- 61 (+/- SE) to 121.8 +/- 30.9 (p less than 0.05). T4 and T3 levels were invariably subnormal at creatinine concentrations greater than 250 mumol/l (2.8 mg/dl), but FT4 was subnormal only in chronic renal failure. Thyroxine binding globulin (TBG) capacity did not change significantly; thus the TBG: T4 ratio increased from 3.4 +/- 0.2 (basal) to 10.4 +/- 3.4 before death (p less than 0.05). In animals which survived for greater than 25 days after transplantation, a significant linear correlation between FT4 and T3 was found as uremia progressed. Polyacrylamide gel electrophoresis (pH 7.4) of (125I)-T4 labelled preoperative and uremic serum showed a consistent decline in the proportion of tracer bound to TBG, from 67.0 +/- 0.8% to 58.9 +/- 1.0% (p less than 0.001), with a 48% reduction in TBG saturation (p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)

[Thyroid function in the nephrotic syndrome]

Serum Total Thyroxine (T4), Triiodothyronine (T3), Free Thyroxine (FT4), Free Triiodothyronine (FT3) Reverse Triiodothyronine and T3 Resin Uptake (T3RU) as well as basal and post stimulating TSH were measured in twenty clinically euthyroid patients with the nephrotic syndrome. In comparison with control values, our patients showed (1) significantly lowered mean serum TBG levels (p less than 0,05) (2) unmodified mean serum T3, FT3 and rT3 values (3) significantly lowered mean serum T4 and FT4 levels (p less than 0,001 and p = 0,027 respectively) (4) significantly higher mean basal TSH, and increased TSH response to TRH. We found a significant correlation between proteinemia and T4 or FT4 (p less than 0,001; p less than 0,01 respectively). In summary, our study: Shows that the low Total T4 observed in the Nephrotic Syndrome is not only due to a decreased protein bound T4, but also to a decreased FT4; And brings evidence for mild hypothyroidism in nephrotic patients.

Neuroendocrine alterations in systemic disease

Systemic disorders clearly may exert a significant influence on neuroendocrine function. Disorders that cause significant stress to the body, either physical or psychological, may cause a resetting upward of the HPA axis to provide sufficient cortisol to counteract the stress and to help sustain energy substrate levels. GH levels also increase in many of these situations, again promoting sufficient energy substrate levels. In some circumstances the concomitantly low somatomedin activity may be speculated to be adaptative to prevent the insulin-like agonist activity of these substances as well as to prevent energy expenditure in body growth. However, in other situations such as chronic renal failure and cirrhosis, the decreased somatomedin activity may be primary, causing decreased feedback at the hypothalamic-pituitary level and increased GH levels. The stress-induced rise in PRL may also play a minor role in preserving energy substrate since high levels may promote insulin resistance. In most illnesses the 'euthyroid sick syndrome' develops. Whether such patients are 'euthyroid' or mildly hypothyroid is a matter of controversy. The fact that protein losses are increased during fasting when the lowered T3 levels are returned to normal with exogenous T3 supplementation suggests that these patients are indeed hypothyroid and this hypothyroidism serves to conserve energy substrate by decreasing the metabolic rate. The reproductive axis is often impaired with systemic illness. Again, teleologically this may be viewed as an inactivation of non-essential functions in times of stress. It would appear that the changes that occur with systemic illness, in general, are favourable to the organism in that they promote survival. The detailed neurotransmitter and hypophyseotrophic hormone changes resulting in the alteration in pituitary function remain to be elucidated for the most part.