TSH response to synthetic thyrotropin-releasing hormone in human protein-calorie malnutrition

Neuroendocrine profile in bulimia nervosa

The neuroendocrinology of bulimia nervosa has only recently been investigated, with initial research suggesting some biological overlap with both anorexia nervosa (AN) and depression. Similarities among AN, depression, and bulimia include a nonsuppressed Dexamethasone Suppression Test and an abnormal growth hormone (GH) response to thyrotropin-releasing hormone (TRH). Bulimics and anorectics both tend to have a delayed thyrotropin (TSH) response to TRH and elevated basal GH levels. Bulimics, however, have a normal GH response to clonidine, a nonblunted TSH response to TRH, low basal prolactin (PRL) levels, and may have an exaggerated PRL response to TRH. Unpublished data suggest bulimics may have a gonadotropin profile distinct from either AN or depression, as well as a variety of other endocrinopathies. Although many of these abnormalities may reflect malnutrition despite normal weight, other factors that are as yet unidentified are likely to be contributing to the neuroendocrine abnormalities seen in bulimia.

Primary hypothyroidism in an adult patient with protein-calorie malnutrition: a study of its mechanism and the effect of amino acid deficiency

A man with diabetes mellitus, chronic hepatitis, chronic pancreatitis, and blind loop syndrome but without any previous thyroid disease developed three episodes of transient primary hypothyroidism associated with protein-calorie malnutrition (PCM). Clinical examinations suggested that this primary hypothyroidism was not caused by chronic thyroiditis, iodine deficiency, or iodine excess. Since the three times association of primary hypothyroidism with PCM suggested the possibility that the primary hypothyroidism was caused by PCM, we have tried to clarify its mechanism. For this purpose we have investigated the change of thyroid functions during protein-calorie repletion and the effect of amino acid deficiency. Total parenteral nutrition with full supplementation of amino acids resulted in a rapid increase in serum thyroxine (T4), triiodothyronine (T3), free T4, and reverse T3, and subsequently, a rapid decrease in TSH in several days after the nutrition was begun. When amino acid solution was changed to that depleted of phenylalanine and tyrosine after the restoration of thyroid functions, serum T4 and T3 showed a gradual decrease, but serum free T4 and TSH remained within normal range. However, resupplementation of phenylalanine and tyrosine after 8 weeks of depletion gave a rapid increase in serum T4, T3, free T4, and reverse T3. These results suggested that the primary hypothyroidism was caused by an impaired T4 production and that the deficiency of amino acids in PCM partly contributed to the impairment of T4 production.

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.

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

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

Dietary amenorrhoea and subclinical hypothyroidism with elevated TSH responsive to weight gain

A case of dietary amenorrhoea associated with the biochemical picture of subclinical hypothyroidism is described. Both the amenorrhoea and the abnormal thyroid function tests reverted to normal on gaining weight.

Abnormal gonadothrophin secretion in children with chronic renal failure

LH and FSH response to intravenous injection of GnRH was evaluated in a group of patients with chronic renal failure on intermittent haemodialysis and in two children with successful renal transplant. Basal plasma LH was elevated in children with chronic renal failure as compared to control, and significantly increased following GnRH injection in most of the children. Basal plasma FSH was higher than in the control group, and slightly increased after GnRH. These data suggest an abnormal response to GnRH in chronic renal failure and an involvement of hypothalamus and pituitary in chronic renal disease. The role of abnormal gonadotrophin secretion in growth retardation and pubertal delay of these children is still not well understood.

Response to thyrotrophin-releasing hormone in atrial dysrhythmias

Seventy-eight clinically euthyroid patients with atrial dysrhythmias, either established or paroxysmal, and sixty-three patients in sinus rhythm with coronary disease were screened for hyperthyroidism using thyroid function tests including the thyroid-stimulating hormone (TSH) response to thyrotrophin-releasing hormone (TRH). All had normal levels of serum thyroxine (T4) apart from three with dysrhythmias who were found to have hyperthyroidism. Twenty per cent of patients with atrial dysrhythmias and 10% of those in sinus rhythm had exaggerated TSH response to TRH. Thirty-six per cent of patients with an exaggerated response of TSH to TRH had significant titres of thyroid auto-antibodies compared with 15% with positive antibodies in those with normal TSH response to TRH. Auto-immune thyroid disease may be more closely related to heart disease than has previously been recognized. Rapid atrial dysrhythmias may occur in the presence of a normal serum thyroxine, high levels of TSH and positive thyroid antibodies.

Decreased serum thyroid hormone levels and increased TSH response to TRH in infants with coeliac disease

Plasma levels of thyrotrophin before and after the intravenous administration of 200 microgram of thyrotrophin releasing hormone have been studied in eleven patients with active gluten-induced enteropathy and in a group of twenty-one normal prepubertal children. In nine out of eleven coeliac patients an exaggerated and/or sustained response of plasma thyrotrophin is observed. Basal plasma thyrotrophin level is not significantly different from the value observed in normal children. However, plasma levels recorded 20 and 60 min after injection of the releasing hormone are significantly higher than in control children (at 20 min: P less than 0.01; at 60 min: P less than 0.001). Serum levels of dialysed triiodothyronine and thyroxine and of triiodothyronine are significantly lower in coeliac patients than in normal infants (P less than 0.01). These data support the evidence of an endocrine dysfunction in coeliac disease. It is not clear whether it is due to malnutrition and/or to some direct action of circulating gluten-peptides on the hypothalamus.

Triiodothyronine and thyroid-stimulating hormone in protein-calorie malnutrition in infants

Protein-calorie malnutrition (P.C.M.) in a group of 43 Senegalese children aged eighteen to thirty months was characterised by a sharp fall in serum-triiodothyronine (T3) concentration to 25-3% of the mean value in healthy age-matched controls. This decrease in T3 was significantly (P less than 0-001) more pronounced in kwashiorkor of recent onset than in long-term P.C.M., a finding which suggests that impaired thyroxine (T4) monodeiodination in the liver was responsible for the fall in serum-T3 concentration rather than a reduction in the secretion of T3 by the thyroid. Serum-T3 concentrations became normal in both malnourished groups after two weeks of appropriate nutrition. Serum-T3 concentrations in healthy, euthyroid, Senegalese children were higher than in White children. In frank kwashiorkor in Senegalese children, serum-thyroid-stimulating-hormone (T.S.H.) concentrations were within the normal range throughout the entire course of dietary therapy, indicating that the children remained euthyroid. In contrast, protracted P.C.M. led to impairment of the T.S.H./T3 feedback mechanism and to a condition resembling hypophysectomy, which required two weeks' dietary therapy for its correction.

Failure of adrenergic alpha and beta receptor blockade to elevate the TSH and prolactin response to TRH in hyperthyroidism

The effects of adrenergic alpha and beta receptor blockade on the thyrotrophin and prolactin responses to TRH were studied in groups of hyperthyroid patients who received either oral propranolol and phenoxybenzamine or intravenous propranolol and rogitine. The flat TSH and prolactin responses to TRH in the untreated hyperthyroid patients were not altered by oral or intravenous adrenergic alpha and beta receptor blockade suggesting that catecholamines do not play a major role in the feedback suppression of TSH and prolactin in hyperthyroidism.