Diagnosis of thyroid dysfunction: present and future

Thyroid disorders represent the second most common endocrine disorder after diabetes mellitus. For this reason, investigation of thyroid function is frequently carried out, taking advantage of numerous tests currently available. It it the physicians's difficult task to select the most appropriate assay(s) in the different pathophysiological conditions from the bewildering array of thyroid function tests, in order to satisfy optimal diagnostic standards, but also to fulfill cost/benefit criteria. Aim of this paper is to provide a brief overview of advantages and disadvantages of main thyroid function tests, and to suggest a testing strategy for the diagnosis of suspected thyroid dysfunction.

Serum interleukin-6 in amiodarone-induced thyrotoxicosis

Amiodarone, an iodine-rich cardiac drug, may induce thyrotoxicosis (AIT), which can occur in patients with preexisting thyroid abnormalities and in subjects with apparently normal thyroid glands. The pathogenesis of AIT is often due to iodine-induced excessive thyroid hormone synthesis, especially in patients with underlying thyroid disease. In some instances, however, AIT may be related to a destructive process due to amiodarone-induced thyroiditis, resulting in thyroid cell damage and thyroid hormone release into the circulation. Another thyroid inflammatory process, subacute thyroiditis, has been recently reported to be associated with markedly increased serum interleukin-6 (IL-6) levels. To investigate the significance of serum IL-6 levels in AIT, we evaluated in a cross-sectional study the following subjects: 27 AIT patients, 15 with no apparent thyroid abnormalities (AIT-) and 12 with nodular goiter and/or thyroid autoimmune disease (AIT+); 14 euthyroid patients receiving chronic amiodarone therapy; 10 patients with amiodarone-induced hypothyroidism; 56 patients with spontaneous hyperthyroidism due to Graves' disease (n = 35) or toxic adenoma/nodular goiter (n = 21); 20 subjects with nontoxic goiter; and 50 healthy controls. Serum free thyroid hormone concentrations did not differ in patients with amiodarone-induced or spontaneous hyperthyroidism. Mean (+/- SE) serum IL-6 values were as follows: AIT-, 573.5 +/- 78.7 fmol/L (range, 149.4-1145.1); AIT+, 152.7 +/- 46.3 fmol/L (range, < 25-505.6); euthyroid patients receiving chronic amiodarone therapy, 51.4 +/- 10.0 fmol/L (range, < 25-122.5); amiodarone-induced hypothyroidism, 43.8 +/- 8.4 fmol/L (range, < 25-84.3); Graves' disease, 108.2 +/- 18.2 fmol/L (range, < 25-250); toxic adenoma/nodular goiter, 97.6 +/- 10.3 fmol/L (range, < 25-168.9); nontoxic goiter, 47.3 +/- 7.1 fmol/L (range, < 25-106.6); and controls, 37.8 +/- 6.2 fmol/L (range, < 25-99.4). Serum IL-6 values in AIT- patients were markedly higher (P < 0.0001) than those in all other groups. Values in AIT+, although slightly higher, did not significantly differ from those in patients with spontaneous hyperthyroidism. AIT- patients had low 24-h thyroidal radioiodine uptake (RAIU), whereas AIT+ had inappropriately low normal to high (9-58%) RAIU values in the presence of excess iodine. The presence of markedly elevated serum IL-6 concentrations and low thyroidal RAIU values in patients with AIT without underlying thyroid disease suggests the presence of amiodarone-induced thyroiditis as the etiology of thyrotoxicosis. Treatment of 2 such patients with prednisone was associated with a dramatic reduction and prompt normalization of IL-6 and thyroid hormone values.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of thyroxine excess on peripheral organs

Aim of this paper is to review the effects of T4 excess due to exogenous thyroid hormone administration on target organs, with particular regard to heart, bone, liver and pituitary. Therapy with TSH-suppressive doses of T4 has been shown in a cross sectional echocardiographic study to increase left ventricular contractility and to induce mild myocardial hypertrophy. Whether the latter represents a risk for the patients remains a matter of debate. Clinically it does not seem to be important. The long-term evaluation of T4-therapy has provided controversial results. Some have reported that T4-treated patients under the age of 65 have an increased risk of ischemic heart disease, whereas others were unable to find any change in morbidity, mortality and quality of life, including cardiovascular events. Thyroid hormones enhance both osteoblastic and osteoclastic activities in cortical and trabecular bone. Overt hyperthyroidism is well known to represent a risk factor for osteoporosis. Studies in the late eighties have suggested a reduced bone density in T4-treated patients, with a particular risk for cortical bone in postmenopausal women. More recent studies have failed to show any substantial T4-related change in bone mass. Taken together the evidence of the literature suggests that TSH-suppressive therapy with T4 is, if well controlled, probably not associated with significant loss of bone mass at least in premenopausal women. A mild elevation of the activity of hepatic enzymes (glutathione-S-transferase, gamma glutamyltransferase, alanine amino-transferase, angiotensin-converting enzyme) has been observed in patients under T4 treatment in TSH-suppressive doses.(ABSTRACT TRUNCATED AT 250 WORDS)

Complex alteration of thyroid function in healthy centenarians

Several changes in thyroid function have been described in the elderly and largely attributed to concomitant nonthyroidal illness. The extent to which aging per se contributes to these changes remains to be elucidated, and scanty data are available in extremely old subjects. The present study was designed to focus on thyroid function during physiological aging, taking advantage of two groups of selected aged individuals: group A of healthy centenarians (n = 41; age range, 100-110 yr) and group B including healthy elderly subjects selected by the criteria of the EURAGE SENIEUR protocol (n = 33; age range, 65-80 yr). Control groups included 98 healthy normal adult subjects (group C; age range, 20-64 yr) and 52 patients with miscellaneous nonthyroidal illness (group D; age range, 28-82 yr). Our previous report of a low prevalence of thyroid autoantibodies in centenarians was confirmed and extended by the finding of a similar low autoantibody prevalence in the highly selected healthy elderly population of group B. Subclinical primary hypothyroidism was found in 3 (7.3%) centenarians, and their data were excluded from further statistical evaluation. No significant difference was found in the median serum free T4 levels of groups A-C. Median (and range) serum free T3 (FT3) was lower in centenarians [3.67 pmol/L (2.3-5.5)] than in group B [5.22 pmol/L (3.4-6.1)] and group C [5.38 pmol/L (2.9-8.4); P < 0.0001 vs. both groups]. Similarly, the median serum TSH level of centenarians [0.97 mU/L (< 0.09 to 2.28)] was lower than those in groups B [1.17 mU/L (0.53-2.74)] and C [1.7 mU/L (0.4-4.8); P < 0.0001 vs. both groups]; moreover, serum TSH was also significantly (P < 0.01) lower in group B than in group C. Both serum FT3 and TSH concentrations showed a significant inverse correlation (r = -0.634; P < 0.0001 and r = -0.377; P < 0.0001, respectively) with age. Median serum FT3 in centenarians was lower than that in group D patients [4.61 pmol/L (2.15-6.6); P < 0.0001]. In contrast, median serum rT3 in centenarians [0.40 nmol/L (0.20-0.77)], although higher than those in groups B [0.24 nmol/L (0.15-0.37); P < 0.0001] and C [0.22 nmol/L (0.05-0.46); P < 0.0001], was significantly lower than that in group D [0.60 nmol/L (0.13-2.08); P < 0.0001]. In conclusion, thyroid function appears to be well preserved until the eighth decade of life if healthy subjects are studied, whereas a reduction of serum FT3 is observed in extreme aging.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroid hormone transport proteins

TBG, TTR, and albumin are quantitatively the most important thyroid hormone binding proteins in humans. Only a minute fraction of T3 and T4 circulates unbound, but it is this free hormone that is metabolically active at the tissue level, and, therefore, responsible for thyroid status. Inherited or acquired variations in the concentration or affinity of these proteins may produce substantial changes in serum total thyroid hormone levels but do not affect serum free thyroid hormone concentrations and, therefore, do not influence actual thyroid status. Thus, thyroid hormone-binding protein abnormalities must be suspected when abnormally elevated or diminished total thyroid hormone concentrations are encountered in clinically euthyroid subjects. This is crucial to avoid erroneous and potentially detrimental treatments for hyperthyroidism or hypothyroidism.

Interleukin-6 inhibits corticosteroid-binding globulin synthesis by human hepatoblastoma-derived (Hep G2) cells

Corticosteroid-binding globulin (CBG) belongs to the superfamily of serine proteinase inhibitors which include alpha 1-antitrypsin, alpha 1-antichymotrypsin, and T4-binding globulin. Interleukin-6 (IL-6), the main mediator of the acute phase phenomenon, increases alpha 1-antitrypsin and alpha 1-antichymotrypsin synthesis and decreases T4-binding globulin synthesis by human hepatoblastoma-derived (Hep G2) cells. This effect is predominantly at a transcriptional level. When Hep G2 cells were exposed to different concentrations of IL-6 for variable time intervals, IL-6 caused a dose- and time-dependent decrease in the amount of [35S]methionine-labeled CBG immunoprecipitated in the culture medium. This effect could be greatly reduced by preincubation of IL-6 with its neutralizing antibody and reversed by removing the cytokine from the culture medium. The secretion rate of CBG was not affected by cell exposure to IL-6. CBG mRNA steady state levels were reduced; changes in mRNA were quantitatively similar to changes in secreted protein. Nuclear run-off assays failed to show a change in the rate of transcription of the CBG gene. These data indicate that IL-6 diminishes CBG synthesis by Hep G2 cells acting at a posttranscriptional level, presumably through a reduced stability of mRNA. In view of the role of IL-6 in the inflammatory process and other acute phase phenomena, these data suggest that its effects on CBG synthesis might influence the bioavailability of cortisol indirectly and play a role in regulating the homeostatic process during these conditions.

Octreotide treatment does not affect the size of most non-functioning pituitary adenomas

The somatostatin analogue, octreotide (OC) has commonly been used in the management of growth hormone- and thyrotropin-secreting pituitary tumors, and shown to be effective both on hormone production and tumor size. Because OC receptors may be expressed also in some nonfunctioning pituitary adenomas, it has been postulated that OC might play a role in the treatment of these tumors as well. In the present study, the morphological effects of OC administration, as assessed by computer tomography (CT) scan, were evaluated in 8 patients (5 men, 3 women, age range 25-79 yr) affected by non-functioning pituitary tumors. The drug was given sc at the dose of 100 micrograms tid for 3-6 months. No significant change in visual field or tumor size occurred after OC treatment in 7 patients, whereas one showed a significant improvement of visual field associated with a decreased tumoral mass. These data suggest that OC is not an effective drug in the management of nonfunctioning pituitary adenomas.

Relationship between nocturnal serum thyrotropin peak and metabolic control in diabetic patients

Circadian variations in serum TSH, especially its nocturnal rise, are often blunted in nonthyroidal illness. We analyzed TSH secretion in 15 diabetic patients (7 with type I and 8 with type II diabetes mellitus). Patients were evaluated when diabetes was poorly controlled (fasting blood glucose ranging from 13.7-19.2 mmol/L with absence of ketoacidosis) and after achieving glycemic control. Before correction of hyperglycemia, the nocturnal serum TSH peak (2230-0200 h) was abolished in 11 of 15 patients (73%); the mean (+/- SE) night TSH/morning TSH x 100 was 109.0 +/- 9.5 (range, 66.7-166.7) vs. a mean of 216.5 +/- 27.0 (range, 139.8-462.5) in normal controls. The mean morning TSH value in diabetics (1.9 +/- 0.4 mU/L) did not differ from that in normal age- and sex-matched controls. The mean TSH increase after iv administration of TRH was only slightly reduced (8.4 +/- 1.2 mU/L pretreatment vs. 10.8 +/- 1.6 mU/L posttreatment), with the TRH test blunted in 3 cases. No differences were found between type I and type II patients. Correction of hyperglycemia was associated with the reappearance of a nocturnal TSH peak in all but 1 patient (mean TSH peak, 198.2 +/- 13.0; P = NS vs. controls). This change paralleled the normalization of serum total T3 and rT3, which were reduced and increased, respectively, when diabetes was poorly controlled. An inverse relationship was found between serum fructosamine levels and the nocturnal TSH peak, suggesting that metabolic decompensation accounts for the abolishment of the latter.

Increased serum interleukin-6 concentration in patients with subacute thyroiditis: relationship with concomitant changes in serum T4-binding globulin concentration

Interleukin-6 (IL-6) is the main mediator of the acute phase response. Increased serum concentrations of the cytokine have been found in patients with nonthyroidal inflammatory disorders and infections. In 18 patients with subacute thyroiditis (SAT) evaluated within 1-2 weeks after the onset of the disease, serum IL-6 values, as assessed by an ELISA method having a limit of detection of 25 fmol/L, ranged 139.2-543.9 fmol/L (mean +/- SE, 287.2 +/- 28.2 fmol/L). These values were significantly higher than those of 25 normal healthy controls (mean +/- SE, 26.2 +/- 5.5 fmol/L, range < 25-99.4), 18 of whom had serum IL-6 values below the detection limit. The increase in serum IL-6 levels in SAT patients appeared to be related to the inflammatory disorder and not to thyrotoxicosis, because 18 Graves' disease patients and 13 patients with toxic adenoma or toxic multinodular goiter had significantly lower serum IL-6 concentrations (101.7 +/- 35.2 fmol/L, range < 25-251, for Graves' disease, 79.6 +/- 41.4 fmol/L, range < 25-168.5, for toxic adenoma, p < 0.001 vs SAT for both groups) despite the markedly higher levels of total and free thyroid hormones. Neither free T4 nor free T3 values were correlated with serum IL-6 levels both in SAT and Graves' patients. Twelve SAT patients were reevaluated 3-4 months later, after remission of the disease and at least one month after glucocorticoid withdrawal. At the final observation, all SAT patients showed a normalization of IL-6 concentration, which was undetectable in 8/12 (mean +/- SE, 22.8 +/- 5.4 fmol/L, p < 0.001 vs acute phase values).(ABSTRACT TRUNCATED AT 250 WORDS)

Circulating antibodies to DNA-related antigens in patients with autoimmune thyroid disorders

A high prevalence of antibodies to double-stranded DNA (AbDNAds) has been recently reported in serum of patients with autoimmune thyroid disorders, but the specificity of this finding has been questioned. For this reason, the prevalence of several antibodies to DNA-related nuclear antigens (AbDRENA) has been evaluated in sera of patients with autoimmune and non-autoimmune thyroid disease. The study group included: 46 Graves' disease patients, 28 Hashimoto's thyroiditis patients, 25 patients with toxic nodular goitre and 11 with non-toxic nodular goitre. Twenty-eight Graves' patients were retested during methimazole (MMI) therapy, and 5 after radioiodine administration. Twenty-two patients with systemic lupus erythematosus and 28 normal subjects served as positive and negative controls, respectively. AbDRENA included: AbDNAds by RIA or immunofluorescence (IF); antibodies to single-stranded DNA (AbDNAss) and antibodies to histone (AbHist) by ELISA methods; antibodies to nuclear antigens (ANA) by immunofluorescence. RIA values were considered to be abnormal when 2 SD above the mean of normal controls. In our study 13% of Graves' patients were positive for AbDNAds by RIA: all of them had negative tests by IF; 11% were positive for AbDNAss, 2% for AbHist and 7% for ANA. A comparable prevalence of positive results for AbDNAds by RIA, with negative IF tests, was found in Hashimoto's thyroiditis patients. No significant changes of antibody levels were observed in Graves' patients during MMI treatment or after radioiodine administration. A positivity for AbDNAds or AbDNAss was found in 8% of patients with toxic nodular goitre, but in none of those with non-toxic goitre.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroimaging and functional outcome of neonatal leukomalacia

Leukomalacia is a major cause of neurological impairment in the high-risk newborn. It can be identified during the early postnatal period by means of ultrasound (US) imaging of the brain, through the anterior fontanel. Magnetic resonance imaging (MRI) permits an optimal differentiation of brain tissue and of its abnormalities, without resorting to ionizing radiation or intravenous contrast. It is particularly appropriate for following the evolution of leukomalacia, after fontanel closure. Ninety-five fullterm and preterm infants with cystic and non-cystic leukomalacia, documented by US, were clinically followed-up until at least 12 months of corrected age. Thirty-two had a severe neurological outcome (mainly cerebral palsy, sometimes associated with mental retardation and/or cerebral visual impairment). The prognosis was worse in cystic leukomalacia than in prolonged flare. Electroencephalogram (EEG) carried out in the first 2 weeks of life provided valuable indexes of further outcome, especially for US findings of more uncertain prognosis. MRI was carried out at around 12 months of corrected age, by means of an apparatus operating at 0.5 Tesla. The main categories of abnormalities observed were the following: cystic lesions, enlarged ventricles with irregular outlines, delayed myelination, high intensity areas in the long TR (repetition time) images within the white matter, cortical atrophy. MRI findings correlated well with the results of US imaging and often with motor, cognitive and visual impairments. Nevertheless, clinical features cannot be predicted by neuroimaging alone and a comprehensive approach, including longitudinal functional and electrophysiological testing, is highly recommended.

Effects of interleukin-6 on the expression of thyroid hormone-binding protein genes in cultured human hepatoblastoma-derived (Hep G2) cells

T4-binding globulin (TBG) shares a high degree of homology with two serpin antiproteases, alpha 1-antichymotrypsin (ACT) and alpha 1-antitrypsin (AT), whose synthesis is increased during the acute phase phenomenon, which accompanies trauma, infections, and neoplasms. Interleukin-6 (IL-6) is believed to be the main effector of the acute phase response. When evaluated in human hepatoblastoma-derived (Hep G2) cells exposed to different doses of the recombinant human cytokine for variable time intervals, IL-6 caused a dose- and time-dependent decrease in the secretion of [35S]methionine-labeled TBG, transthyretin (TTR), and albumin. The secretion of ACT and AT was increased. These changes were not due to alterations in the secretory process, since the kinetics of secretion of newly synthesized proteins were not modified. IL-6 did, however, cause a decrease in the steady state levels of mRNA for TTR, TBG, and albumin and an increase in ACT and AT mRNAs. In addition, nuclear run-off assay demonstrated a decrease in the transcription of TTR, TBG, and albumin genes and an increased transcription of the ACT gene. Quantitation of the results showed that changes in the secretion of proteins, in steady state mRNA levels, and in gene transcription were superimposable for each protein, indicating that IL-6 exerts its effect on thyroid hormone-binding proteins mostly at the transcriptional level and that TTR is the thyroid hormone-binding protein showing the most pronounced negative regulation by IL-6. The opposite effect of IL-6 on TBG and the antiproteases, despite their structural homology, underscores gene divergence among these proteins.

Gastrin (G) cells are the cellular site of the gastric thyrotropin-releasing hormone in human fetuses and newborns. A chromatographic, radioimmunological, and immunocytochemical study

In this study we analyzed the ontogeny and location of gastric TRH in human fetuses, preterm and term newborns, and adults. TRH immunoreactive cells were found in the antrum towards the bottom of developing glands and double immunostaining demonstrated that this neuropeptide is coexpressed with gastrin in the same cell (G-cell). In the youngest fetuses studied (12 weeks) G cells were few and contained both gastrin and TRH. They increased in number during development and were most abundant between 26 and 36 weeks of gestation. These morphological data correlated with total immunoreactive TRH content extracted from the whole stomachs of six fetuses and two preterm infants. On the contrary G cells containing both hormones were decreased in the newborn at term and not identified in the adult whereas those containing only gastrin were numerous in both. The TRH extracted was indistinguishable from synthetic TRH using chromatographic, radioimmunologic, and enzymatic criteria. As has already been reported, TRH was found in insulin-containing cells of the islets of Langerhans in the pancreas of our fetuses and newborns. These cells presented a similar development pattern to the gastric G cells.

Iodine contamination in subjects admitted to a general hospital

Urinary iodine excretion was measured in 300 consecutive patients admitted to a general hospital for nonthyroidal disease. Iodine contamination (values greater than 300 micrograms l/g creatinine) was found in 29.3% of cases, mostly due to amiodarone and iodinated contrastographic agents. The source of iodine contamination was not detected in 23% of cases.

Relationship between Graves' ophthalmopathy and type of treatment of Graves' hyperthyroidism

The relationship between the treatment of Graves' hyperthyroidism and the course of ophthalmopathy is rather unclear. Antithyroid drugs may improve eye manifestations, possibly by restoring normal thyroid function and reducing orbit-directed autoimmune reactions, whereas ophthalmopathy may worsen after radioiodine administration or thyroidectomy. This might occur because of a treatment-related release of thyroid antigens and activation of the autoimmune response that might involve the orbit. On the other hand, some authors suggest that complete thyroid ablation, either by radioiodine or surgery, might be beneficial for ophthalmopathy. However, reported effects of radioiodine and thyroidectomy on Graves' ophthalmopathy are conflicting. This may be due, at least in part, to the retrospective feature of most studies and the lack of precise evaluation of ocular involvement. Two prospective studies were performed in which patients with Graves' disease with mild or no ophthalmopathy were randomly assigned to treatment by radioiodine or subtotal thyroidectomy alone or in association with systemic glucocorticoids. Both treatments were followed by a progression of pre-existing mild ophthalmopathy in a substantial proportion of cases: glucocorticoids prevented such an exacerbation. Ophthalmopathy did not develop in patients without clinical evidence of eye disease prior to therapy. Therefore, it is recommended that a course of glucocorticoids be instituted concomitantly with radioiodine therapy or thyroidectomy in Graves' patients with some degree of ocular involvement.

Variations in thyroid hormone transport proteins and their clinical implications

Variations in major thyroid hormone transport proteins may be inherited or acquired and may be associated with changes in serum concentration of the proteins or their affinity for thyroid hormones. These variations most frequently involve thyroxine-binding globulin (TBG), but changes in transthyretin and albumin are also observed. The consequent alteration of thyroid hormone-binding capacity in serum is associated with variations in total thyroid hormone concentration. Increased serum total thyroid hormone levels are found in subjects with TBG excess, familial dysalbuminemic hyperthyroxinemia, and transthyretin-associated hyperthyroxinemia. Conversely, diminished serum thyroid hormone values are observed in subjects with TBG deficiency, and decreased concentration or affinity of transthyretin and albumin is not associated with variations in serum concentrations of thyroid hormones. The transport protein-associated variations in serum total thyroid hormone concentrations do not reflect a change in thyroid status. Euthyroidism can be easily established in subjects with transport protein abnormalities by the normal free thyroid hormone and TSH concentrations. It is, however, crucial to select methods for free thyroid hormone measurement that are not affected by abnormalities of transport proteins. Some assays, such as the analog method, often provide artifactual and misleading results, which may lead to inappropriate and even detrimental treatments. The evolutionary advantage of TBG (and albumin) in terms of thyroid homeostasis still remains to be elucidated.

Orbital radiotherapy combined with high dose systemic glucocorticoids for Graves' ophthalmopathy is more effective than radiotherapy alone: results of a prospective randomized study

We have carried out a prospective study to investigate whether orbital radiotherapy combined with high dose systemic glucocorticoids is more effective than orbital radiotherapy alone for Graves' ophthalmopathy. Thirty consecutive patients with relevant and active Graves' ophthalmopathy were randomly assigned to treatment either with orbital radiotherapy combined with systemic glucocorticoids (Group 1, n = 15) or with orbital radiotherapy alone (Group 2, n = 15). The final evaluation was made 6-9 months after beginning treatment. Two patients in each group were lost to follow-up. Ocular involvement and response to treatment were evaluated by the ophthalmopathy index and by clinical assessment. Mean ophthalmopathy index values were 5.85 in Group 1 and 5.46 in Group 2 (p = NS) before treatment, and 2.46 in Group 1 and 3.61 in Group 2 after treatment (p = 0.0001 and p = 0.003 vs initial value, respectively). The mean ophthalmopathy index decrease in Group 1 (-3.39) was significantly greater (p = 0.043) than that in Group 2 (-1.85). Favorable responses on clinical ground occurred in 9 patients (69%) in Group 1 and in 5 patients (38%) in Group 2. The difference was particularly evident on soft tissue changes and extraocular muscle involvement. Severe eye muscle restriction was substantially unaffected by either treatment. In conclusion, the association of orbital irradiation and high dose systemic glucocorticoids in the treatment of severe Graves' ophthalmopathy provides more favorable responses than orbital radiotherapy alone.

Therapy of Graves' disease with sodium ipodate is associated with a high recurrence rate of hyperthyroidism

To evaluate the long-term efficacy of sodium ipodate (IPO) in the treatment of hyperthyroid Graves' disease, we studied 12 consecutive patients with Graves' hyperthyroidism treated only with 500 mg IPO po daily for several weeks to 22 months. Serum thyroid hormone concentrations markedly decreased and serum free T3 values normalized in all patients within 7 days of therapy. Five patients (42%, Group 1) were euthyroid after 6 weeks of IPO treatment and remained so until IPO was discontinued after 22 months. Recurrence of hyperthyroidism after drug withdrawal occurred in only one of these Group 1 patients, who was promptly responsive to a second course of IPO. In contrast, seven of 12 patients (58%, Group 2) relapsed with recurrent hyperthyroidism between 14 and 42 days of IPO therapy. After IPO was withdrawn, these Group 2 patients were treated with methimazole (20-30 mg/day, initial dose), but the therapeutic response was poor and delayed. Two patients were still hyperthyroid after 6 months of methimazole treatment. Elevated serum FT3 concentrations were observed in the Group 2 patients at 21 days following the early normalization of serum FT3 concentrations. No changes in serum thyroglobulin and thyroid microsomal and TSH-receptor autoantibody titers were observed in either groups during IPO therapy. In conclusion, the results of the present study demonstrate that IPO rapidly restores euthyroidism, but its prolonged administration is associated with a high rate of relapse of hyperthyroidism and a poor response to subsequent methimazole treatment and that long-term IPO administration does not affect humoral markers of thyroid autoimmunity.

The lack of nocturnal serum thyrotropin surge in patients with nontoxic nodular goiter may predict the subsequent occurrence of hyperthyroidism

TSH secretion, with particular regard to the nocturnal TSH surge, was evaluated in 115 subjects with non-toxic nodular goiter. All patients were clinically and biochemically euthyroid. After 18-36 months of follow-up (mean, 24 months), hyperthyroidism occurred in 21 (18%; group 1), while the remaining 94 remained euthyroid (82%; group II). The analysis of hormonal data at the time of first observation showed that the 2 groups had similar total and free T4 and T3 serum concentrations. Morning serum TSH values in group I were lower than those in group II patients (0.6 +/- 0.1 vs. 1.1 +/- 0.1 mU/L; P less than 0.001); this difference was even more striking for the nocturnal values (0.6 +/- 0.1 vs. 2.2 +/- 0.2 mU/L; P less than 0.0001); nocturnal values were significantly lower than morning values in group II, but not in group I. The mean peak TSH value after TRH was also significantly reduced in group I (5.5 +/- 0.4 vs. 9.2 +/- 0.7 mU/L; P less than 0.001). Morning TSH values in group II did not differ from those in controls (1.3 +/- 0.1 mU/L), whereas nocturnal and TRH stimulated peak TSH values were slightly but significantly lower. The nocturnal serum TSH values in control subjects were 62-390% higher than morning values. The nocturnal TSH surge was abolished in 18 of 21 (86%) group I patients and in 7 of 94 (8%) group II patients. TRH testing resulted in an absent or blunted TSH responses in 5 subjects in group I and 6 in group II. Analysis by the Galen and Gambino predictive model; comparing the abolition of the nocturnal TSH surge and the abnormal TRH test as predictors of the subsequent occurrence of hyperthyroidism, showed that the former had higher sensitivity (86% vs. 24%) and predictivity (72% vs. 45%). In conclusion, the results of the present study demonstrate that the evaluation of the nocturnal TSH surge may be useful in identifying patients with nontoxic nodular goiter in whom hyperthyroidism may eventually occur. Patients who lack the nocturnal serum TSH surge are more prone to develop thyroid hyperfunction; their thyroid status should, therefore, be more carefully and frequently monitored.

The nocturnal serum thyrotropin surge is abolished in patients with adrenocorticotropin (ACTH)-dependent or ACTH-independent Cushing's syndrome

TSH secretion was evaluated in 10 patients with ACTH-dependent (pituitary microadenoma, n = 5) or ACTH-independent [adrenal adenoma (n = 4) or carcinoma (n = 1)] Cushing's syndrome, and in 12 normal controls matched for age and sex. Serum TSH concentration was assayed at night, from 2200-0200 h, and in the morning, both basally and 30 min after iv injection of 200 micrograms synthetic TRH. Patients with hypercortisolism showed significantly reduced serum total T4 and T3 and free T3 concentrations and increased serum reverse T3 levels. Their mean baseline serum TSH concentration in the morning, albeit slightly lower, did not significantly differ from those of controls. The mean peak TSH value after TRH was significantly reduced, and a blunted TSH response to TRH was found in 4 out of 10 patients. At variance with normal controls, who showed nighttime TSH values 63-228% higher than morning values, 9 out of 10 patients had nighttime levels not different from or even lower than those in the morning; the remaining patient had nighttime TSH values marginally (33%) higher than in the morning. An inverse relationship (r = 0.80, P less than 0.001) was found between serum cortisol and TSH values both at night and in the morning. No differences were found either in the pattern of TSH secretion or in the TSH response to TRH between patients with ACTH-dependent and those with ACTH-independent Cushing's syndrome. These results show a substantial impairment of TSH secretion, and in particular the loss of the nocturnal surge of the hormone, in patients with Cushing's syndrome. Although the origin of the nocturnal TSH rise is probably multifactorial, cortisol, at least when secreted in excess, appears to play an important role in its regulation.