Control of thyrotropin secretion in man

Central diabetes insipidus and hypothalamic hypothyroidism associated with aceruloplasminemia

Aceruloplasminemia is a rare autosomal recessive disease first reported by Miyajima et al. (Neurology 37: 761-767, 1987); it is clinically characterized by diabetes mellitus, retinal degeneration and neurological abnormalities, such as cerebellar ataxia, extrapyramidal signs and dementia. Aceruloplasminemia is caused by mutations in the ceruloplasmin gene, which results in the absence of serum ceruloplasmin and iron overload in the brain, liver, pancreas and other organ tissues. However, little is known about endocrine diseases associated with aceruloplasminemia. We report herein a case of aceruloplasminemia accompanied by central diabetes insipidus and hypothalamic hypothyroidism.

Thyroid and pituitary hormone responses to TRH in advanced nonalcoholic liver disease

Basal T4, T3, TSH, prolactin and growth hormone levels were determined in several groups: patients with postnecrotic cirrhosis with hepatocellular carcinoma (n = 14); patients with postnecrotic cirrhosis but without hepatocellular carcinoma (n = 26); cholangiolar carcinoma (n = 9); and normal controls age-matched to within 5 yr of the liver disease subjects studied. In addition, TRH stimulation (400 micrograms TRH) was performed; TSH, prolactin and growth hormone responses over a 180-min time interval were evaluated for each subject. The responses observed varied between liver disease groups. The presence or absence of hepatocellular carcinoma was found to determine, at least in part, the type of response observed. Similarly, the presence or absence of hepatic encephalopathy determined, and/or reflected, at least in part, the type of response observed. Finally, for purposes of continuity, basal and TRH-stimulated levels of TSH, prolactin, growth hormone, T4 and T3 are compared in 3 settings of cirrhosis: alcoholic, nonalcoholic postnecrotic cirrhosis, and postnecrotic cirrhosis with hepatocellular carcinoma.

Natural history of primary myxedema

It is generally admitted that primary myxedema in adults is the outcome of autoimmune atrophic thyroiditis. The present review traces the natural history of this process from its incipient biologic and genetic anomalies up to its protracted asymptomatic course, clinical development, and eventual lethal complications. The apprehension of preclinical hypothyroidism may change a clinician's outlook on early diagnosis and therapy.

Endocrinologic and psychologic aspects of galactorrhea associated with normal menstrual cycles

Twelve cases of galactorrhea in women with normal menstrual cycles who were radiologically free of any pituitary adenomas were investigated. Determinations were made for serum thyroid-stimulating hormone (TSH), T3 resin uptake (T3RU), total thyroxine by radioimmunoassay (T4), free thyroxine index (FT4I), norepinephrine, epinephrine, prolactin and urinary luteinizing hormone, total estrogens, pregnanediol and total catecholamines. Psychologic evaluation and assessment were also done using the Middlesex Hospital Questionnaire and the Eysenk, manual dexterity, Bender Gestalt and trial-making scales. Hypothyroidism associated with moderate hyperprolactinemia and anovulation were the main features in eight cases. Associated psychologic disturbances were reported. The other four cases showed significant elevations in serum epinephrine, norepinephrine and urinary total catecholamines with concomitant pathologic scales of anxiety and neuroticism. Thyroxine replacement and psychotherapy are recommended in the treatment of such cases.

Neurotransmitter control of hypothalamic-pituitary-thyroid function in rats

The possible roles of monoamine neurotransmitters in the regulation of the hypothalamic-pituitary-thyroid axis were examined in the rat. Rats were treated acutely and repeatedly with drugs which are presumed to alter neurotransmitter functional activity. These drugs include neurotransmitter precursors (tryptophan and L-DOPA), synthesis inhibitors (p-chlorophenylalanine and alpha-methyltyrosine), uptake inhibitors (desipramine and zimelidine) and lithium carbonate. The hormone levels measured were hypothalamic TRH and SLI content and serum TSH, T4 and T3. We conclude that augmented serotonergic or dopaminergic activity may inhibit TRH release, but that release from these inhibitions is not sufficient to stimulate TRH release. The release of TRH seems to be mediated by norepinephrine. Lithium treatment results in increased hypothalamic TRH.

Disorders of endocrine function following cancer therapies

There is a growing body of literature detailing the endocrine consequences of cancer therapy. Certain conclusions can be drawn from the data presented. Patients who have received incidental hypothalamic--pituitary gland irradiation need to be followed carefully with serial dynamic hormonal evaluations, as they are at high risk of developing growth hormone and prolactin abnormalities and can develop other pituitary tropic hormone deficiencies as well. Children especially should be monitored closely as GH deficiency can be corrected if detected early. Patients who have received radiation to the head and neck region will need long-term (up to 30 years) surveillance for the development of thyroid cancer, hyperparathyroidism or hypothyroidism. Persistent elevations of TSH after incidental thyroidal irradiation are frequently seen and should be reversed with thyroid hormone administration in an attempt to minimize TSH stimulation of the irradiated gland. Radiation to the gonads will cause graded damage dependent on the dose delivered and the mode of fractionation. Age in a woman seems to be a significant factor of radiation sensitivity. Certain chemotherapeutic agents are radiomimetic in their gonadal effects; to date the alkylating agents have been most commonly implicated. FSH elevations herald gonadal damage (aspermia or loss of follicles) and should be looked for in patients receiving abdominal radiation or systemic chemotherapy. Leydig cell dysfunction occurs less frequently. Of all the iatrogenic endocrine complications discussed, some are eminently treatable, and some are quite preventable. Greater awareness of the unexpectedly high incidence of hormonal dysfunction can help lessen therapy-induced morbidity in long-term cancer survivors.

Thyroid-stimulating hormone (tsh), triiodothyronine (t3) and thyroxine (t4) response to intravenous and oral stimulation with synthetic thyrotropin-releasing hormone (trh) in young healthy adults

TSH, T3 and T4 response to stimulation with thyrotropin releasing hormone (TRH) has been investigated in 24 young healthy adults after intravenous injection and in 25 young healthy adults upon oral application of 40 mg of TRH. After intravenous injection the TSH concentration raises from a mean of 1.6 to a mean maximum of 11.7 muU/ml. A statistically significant sex difference could not be found. T3 shows a statistically significant increase which is however too small to be of diagnostic value in an individual test. After oral stimulation with 40 mg of TRH, TSH rises to a slightly higher maximum of 13.2 muU/ml after 3 h. The T3 increase from 1.5 to 2.19 ng/ml is significant and considerably higher than after intravenous stimulation. The thyroxin increase is statistically significant. The present results compare well with previously published data for intravenous stimulation. The oral route of TRH application has not yet been widely used and the present series establishes the normal response in young healthy adults. Repetitive stimulation with three times 40 mg of TRH leads to a decrease in TSH stimulation which reaches 5.8 muU/ml 3 h after the third dose. This is in contrast to a comparable increase in plasma T3.

Mathematical model of pituitary thyrotropic function

A nonlinear differential equation is used to develop a mathematical model describing the time course of thyrotropin (TSH) concentral to real data shows that pituitary responsiveness to TRH is highest in euthyroidism, reduced in primary hypothyroidism, and lowest in hyperthyroidism.

Serum thyrotrophin determination on day 5 of life as screening procedure for congenital hypothyroidism

In 327 newborns cord blood thyroxine (T4) was 11.8 +/- 0.4 mug/100 ml (SEM) (151.9 +/- 5.1 nmol/l), and serum thyrotrophin (TSH) 6.7+/-1.0 muU/ml. Variability was marked for both T4 and TSH. Remeasured in the same patients on the fifth day of life, the TSH level was 3.7 +/- 1.0 muU/ml, lower than at birth (P less than 0.001), while scattering of TSH values was much smaller, with 99.4 % of values less than 12 muU/ml...

Dissociation between TSH and prolactin dynamics in treated thyrotoxicosis

TSH and prolactin secretory patterns in thyroid disease have generally been reported as concordant. We studied TSH and prolactin responses to TRH infusion (500 mug) in euthyroid individuals previously treated for thyrotoxicosis with 131I or antithyroid drugs. The 131I-treated group (seven men, twenty women) had been clinically and biochemically euthyroid (normal serum thyroxine and triiodothyronine levels) for 6 months to 4-5 years (kappa +/- SD = 17-1 +/- 4-1 months). Based on maximal TSH increment (deltaTSH), three patient groups were identified: Group 1 [normal deltaTSH, n = 6]: delta prolactin was normal in two, blunted in one and exaggerated in three. Group 2 (exaggerated TSH response, n = 8): delta prolactin was normal in two, blunted in one and exaggerated in five. Group 3 (TSH nonresponders, n = 13): delta prolactin was normal in five, blunted in three, and exaggerated in five. Eleven patients (three men, eight women) were studied after 6 months antithyroid-drug treatment. All were clinically and biochemically euthyroid. All but one showed a blunted TRH-TSH response. All three men showed an exaggerated delta prolactin as did four of eight women. Three women showed a blunted delta prolactin and in one, delta prolactin was normal. Thus, TRH-induced TSH and prolactin response patterns in treated thyrotoxicosis are not uniformly concordant, and, while a blunted or absent TSH response commonly persists long after euthyroidism has been restored, this is most frequently accompanied by a normal or exaggerated prolactin response.

Defects of taste and smell in patients with hypothyroidism

Taste and smell functions were measured in 18 unselected patients with untreated primary hypothyroidism, and in 15 of the 18 patients after treatment with thyroid hormones. Before treatment, 9 of the 18 patients (50 per cent) were aware of some alteration in their sense of taste, and 7 of the 18 patients (39 per cent) were aware of some alteration in their sense of smell. Distoritions of tase (dysgeusia) and smell (dysosmia) were frequent complaints among the untreated patients; dysgeusia was observed by 7 patients (39 per cent) and dysosmia by 3 patients (17 per cent). Median detection and recognition thresholds for four taste stimuli salt (sodium chloride), sweet (sucrose), sour (hydrochloric acid) and bitter (urea), and for two smell stimuli (pyridine and nitrobenzene), were determined in each patient before and after treatment with thyroid hormones. Before treatment, decreased taste acuity (hypogeusia) for at least one stimulus was observed in 14 of the patients (83 per cent); the most common abnormalities were in the detection and recognition of bitter stimuli. Median detection thresholds for both smell stimuli were also markedly elevated (hyposmia) before therapy. Treatment with throid hormones largely reversed both the taste and smell defects. In one patient, taste and smell abnormalities were completely corrected after 16 days of treatment with thyroxine. This study indicates that taste and smell defects are common clinical abnormalities in primary hypothyroidism, and suggests that these defects may contribute to the anorexia and lack of interest in eating which are frequently observed.

Radioimmunoassay and the hormones of thyroid function

Radioimmunoassay (RIA) has provided the tools for wide-reaching investigations that have changed and continue to change many important concepts of thyroid physiology and pathosphysiology. The RIA vor human thyrotropin (TSH) was developed in 1965; development of the RIA for triiodothyronine (T3), thyroxine (T4), thyroxine-binding globulin (TBG), and, recently, thyrothropin-releasing hormone (TRH) and thyroglobulin (Tg) followed. The capacity to measure nanogram and picogram concentrations with relative ease and speed has permitted the demonstration of dynamic relationships of the intrathyroidal and circulating thyroid hormones to each other and to the pituitary and hypothalamic regulating hormones. Evidence for the presence of cross-influences between TRH and other hypothalamic regulating hormones on the secretion of pituitary hormones has accumulated. The impact of the new information on clinical practice is now becoming evident. There is new appreciation of the value of assaying serum T3 and TSH concentrations in the clinical management of patients with disturbed function of the thyroid, pituitary, or hypothalamus. The necessary components for RIA performance can be purchansed separately or in kit form from commercial sources. With appropriate quality-control procedures, precise, sensitive, and reliable data can be generated. Awareness of the specific technical problems relating to the RIA of these hormones is absolutely necessary to assure reliable results. The availability of kits or their components permits the performance of these studies in the community hospital and in reliable commercial-service laboratories.

In vitro testing of thyroid function: a review

Triiodothyronine (T(3)) is the major thyroid hormone and thyroxine (T(4)) may be only a "prohormone". A normal serum T(3) concentration can compensate for a low serum T(4) to maintain euthyroidism and on the other hand hyperthyroidism can exist in spite of a normal T(4) if the T(3) concentration is increased ("T(3)-toxicosis"). A raised serum thyroid stimulating hormone (TSH) concentration is the present most sensitive indicator of thyroidal hypothyroidism and the level can be used to titrate replacement therapy to the individual's own requirements. TSH concentration is classically low in hypothyroidism secondary to pituitary or to hypothalamic disorder and synthetic thyrotrophin release hormone can then be used to identify which of these two sites is at fault. Thyroxine is the best form of thyroid replacement for hypothyroidism because it produces more consistently physiological concentrations of T(3). Full replacement is achieved with 0.1 - 0.2 mg of T(4)/day and doses above this, as formerly widely used, may cause over-replacement. New reliable kit tests are available which give in one quick procedure a measure of free-thyroxine even in the presence of abnormalities of protein-binding. These kit tests are suitable for the routine screening of the whole spectrum of thyroid dysfunction and when combined, in appropriate instances, with radioimmunoassay procedures for serum T(3) and TSH, provide a battery of tests which will help in the diagnosis of the great majority of causes of thyroid dysfunction.