Thyroid function and plasma immunoglobulins in subjects with Down's syndrome (DS) during ontogenesis and zinc therapy

Thyroid function parameters and immunoglobulin concentrations in sera of outpatients with Down's syndrome (DS, n = 110) of different ages (DS1 = 1-9 years; DS2 = 6-15; DS3 = 15-35) were compared with those of age-matched controls (n = 110). Although mean serum TSH was higher in all DS groups, thyroid hormone concentrations were significantly lower only in DS3. In DS1, a notable frequency rate of high T4 and T3 was found. Serum concentrations of thyroxine binding globulin (TBG) were significantly higher in all DS groups. Free T4 and T3 indexes, calculated as the ratio of total hormone: TBG concentrations, were lower in all DS groups. IgA serum concentrations were significantly higher in all DS groups, IgA was higher in DS1 and DS2. Serum zinc levels were lower in all DS groups. Repeated examination after one year revealed lower T4 and higher TSH in DS patients treated with zinc during this interval as compared to values observed before treatment. Our results suggest a high occurrence rate of complex immune and endocrine disorders with thyroid dysregulation in DS patients, with zinc deficiency playing a considerable role.

Pancreastatin-like immunoreactivity in the pancreas of newborn rats

Pancreastatin (PST), a novel COOH-terminally alpha-amidated peptide is a part of Chromogranin A molecule. Precursor processing implies also the final amidation step dependent on peptidylglycine alpha-amidating monooxygenase (PAM). High activity of PAM as well as Thyroliberin (TRH, another alpha-amidated peptide) concentration and biosynthesis were reported to be very high in neonatal rat pancreas. We followed the concentration of PST-like immunoreactivity in rat pancreas during ontogenesis. High perinatal PST concentration, resembling that of previously reported for PAM activity and TRH concentration was found. These findings suggest that perinatal PAM activation may affect a broader spectrum of pancreatic peptides.

[Hormones and bioactive substances in milk--rudiments or physiologic signals?]

Human milk and milk of lower mammals contains hormones, growth factors, as well as secondary messengers. It can be supposed that in the past this composition secured a better survival for the offspring in a certain phase of development. The question is, what role do the factors play in the physiological development today. They certainly affect the mammary gland at its own right, there is evidence about a positive effect on the intestinal mucosa of infants, even on the regulation of hormonal secretion. Hence, they represent signals sent by the maternal organism and affect the reaction of infants. Whether these effects are physiologically significant in animals and especially in humans still remains to be proved. A very rapidly progressing research promises many interesting and surprising findings in the near future. Objective evaluation of effects of milk composition on the offspring neither allows us to ignore the possibility of negative consequences in postreproductive age, since these signs are not being eliminated by natural selection during evolution.

Search for optimal age for weaning. Ten-year prospective study

The effect of infant nutrition on some clinical and biochemical parameters was studied from birth in a longitudinal prospective study. The data covering the period up to 7 years were reported previously. At the age 10 years 80 children were examined. Two children have been regularly followed up because of high blood pressure. Both had been breast-fed for less than one week and are obese at present. Surprisingly serum total cholesterol was the highest in the group breast-fed for more than 6 months. There were no pronounced differences in the levels of lipoprotein cholesterol carriers. The incidence of a high (over 6.0) atherogenic index (total chol - HDL chol) x APOB/APOA1 x HDL chol) and cholesterolemia over 4.8 mmol/l was significantly (chi 2 test) higher in the group breast-fed for over 6 months. Thyroid function parameters were not affected by the duration of breast-feeding. We conclude that besides undoubtedly favorable effects of breast-feeding, some functions might be also adversely affected if it lasts for more than 6 months. For justified recommendation of optimal duration of breast-feeding all aspects should be considered and more data collected.

Passive immunization and hypothalamic peptide secretion

Passive immunization is a common approach used to eliminate the biological activity of an endogenous substance by its binding to a specific antibody (Ab). Surprisingly little information has been gathered on the mechanisms involved. Moreover, the possibility that immunoneutralization could affect also the secretion of the antigen itself has been mostly ignored. To study hypothalamic neuropeptide secretion under the condition of passive immunization, labeled and unlabeled monoclonal antibody (MoAb) against arginine vasopressin (AVP) was injected intravenously. After 2 h a similar amount of 125I-MoAb was found in hypophyseal portal and peripheral (femoral artery) plasma, showing a distribution volume of 73.2 ml/kg. Assessment of the MoAb dilution in the same plasma samples from the binding studies revealed substantially higher dilutions (800-5,700 ml/kg). Such a MoAb dilution (saturation) would be attained by the binding of 130-290 pmol AVP/ml plasma. The calculated amount of plasma AVP decreased by one half within the interval from 2 to 24 h after Ab injection, similarly as did the 125I-MoAb content. Intravenous injection of polyclonal corticotropin-releasing hormone (CRH) Ab resulted in a decrease of plasma adrenocorticotropin and corticosterone levels. After 24 h the dilution of the Ab in portal plasma exceeded two times that in peripheral plasma. CRH concentrations of 0.6-2.5 pmol/ml were found by specific radioimmunoassay after its dissociation from the Ab in plasma. The CRH concentration was higher in portal than in peripheral plasma and was related to the amount of the Ab injected. CRH mRNA levels in the paraventricular nucleus were significantly increased in CRH Ab as compared with normal rabbit serum injected rats.(ABSTRACT TRUNCATED AT 250 WORDS)

TRH analogs with 4-nitro- and 4-N-butyloxycarbonylamino-1-methyl-2-pyrolylcarboxylic acid in position 1. Synthesis and biological properties

Two new analogs of thyrotropin-releasing hormone (TRH), obtained by the replacement of the L-pyroglutamic acid residue with 4-nitro- or 4-N-butyloxycarbonylamino-1-methyl-2-pyrolylcarboxylic acid (analogs 1, 3), and three related derivatives, in which also the L-histidine residue was replaced with L-norvaline (analogs 2, 4) or L-norleucine (analog 5), were synthesized and tested for endocrine and central nervous system (CNS) activity. The replacement of the L-pyroglutamic acid residue with 4-nitro-1-methyl-2-pyrolylcarboxylic acid (analogs 1 and 2) resulted in the separation of the endocrine from the direct CNS activity. The effect of these analogs on the sleeping time, rectal temperature and breathing frequency, was either the same or greater than that of TRH. However, neither the correlation between the binding of analogs to TRH receptors in the brain nor their activity on the CNS parameters measured was found. Analogs 3, 4 and 5, containing 4-N-butyloxycarbonylamino-1-methyl-2-pyrolylcarboxylic acid in place of L-pyroglutamic acid, were inactive.

Hormones and bioactive substances in milk: a rudiment or a message?

The composition of milk is the result of an evolutionary process with both positive and negative natural selection mechanisms where variants with components supporting offspring development from birth to reproduction (but not later) are preferred. Almost all known hormones and many other bioactive substances are present in milk of various species. Some of them are synthesized by the mammary gland, the others are passively or selectively transported (and eventually modified) from blood into milk. Hormones in milk are of importance for the regulation of the functions of the mammary gland itself. There are indications that they affect (sometimes permanently) both functions of suckling GIT and other functions after their resorption during the defined developmental periods. The definite role of these messages for further offspring development remains to be established.

Two novel thioamide analogues of TRH with selective activity on CNS

TRH analogues containing C-terminal tioamide group and norvaline ([Nva2, Prot3] TRH) or norleucine ([Nle2, Prot3] TRH) in position 2 were synthesized and tested for hormonal and central nervous system (CNS) activities. Receptor binding studies revealed that the analogues neither bind to pituitary nor to brain TRH receptors. Accordingly, no TSH releasing activity was recorded. However, both analogues significantly affected sleeping time and breathing frequency. Dissociation of endocrine effects from those on the CNS of [Prot3] TRH was achieved with the replacement of histidine2 by aliphatic amino acids. The presence of central histidine is not essential for the analogues to be active on the CNS.

Late effects of breast-feeding and early weaning: seven-year prospective study in children

The effect of breast feeding on some clinical and thyroid function parameters was studied in a prospective longitudinal study from birth up to 7 years of age. At the ages 1-7 years, the obesity rates observed in children breast-fed for less than 3 months were substantially higher than in children who had been breast-fed over longer intervals. Mean age when obesity was reported was similar in all groups (4-5 years). The rates of respiratory tract diseases were found to be highest in children which had been breast-fed for less than 2 weeks. Breast-feeding for more than 6 months had a protective effect against diseases of the gastrointestinal tract. The longitudinal follow-up revealed biphasic changes of thyroid hormones and TSH in sera with a nadir at 2-3 years, followed by an increase at the end of preschool age. Duration of breast-feeding did not affect profoundly these parameters at the ages 1-7 years. Surprisingly, during late preschool age (5-6 years) total serum cholesterol increased with the age at weaning. The atherogenic index in 6-year-old children was most favourable in the group breast-fed over more than 1 but less than 3 months. This was due to the highest levels of HDL-cholesterol in this group. We conclude that the age at weaning may be important for the later development of children.

Thyroliberin (TRH) and TRH free acid (TRH-OH) present in milk do not originate from local synthesis in mammary gland

Hypothalamic hormones represent a peculiar group of hormones present in milk in surprisingly high concentrations. High levels of these neuropeptides raised the question of their origin. The hypothesis suggesting local synthesis of TRH in the mammary gland was, therefore, tested. Acid extracts of human milk contained TRH and TRH-OH immunoreactivity. RIA determinations at various purification steps revealed that only a part of the immunoreactivity may represent authentic peptides. No high molecular weight TRH precursor could be demonstrated upon a sequential enzymatic treatment of human milk and rat mammary gland extracts. Exploration of rat mammary gland tissue for TRH mRNA showed that the TRH gene is not expressed in the mammary gland. Rat mammary gland homogenates were able to deamidate exogenous TRH to TRH-OH.

CONCLUSION

TRH is not synthesized in the mammary gland via a high molecular weight precursor. It is likely that the TRH-free acid in milk (demonstrated for the first time in this product) originates from TRH deamidation in mammary gland cells during TRH transport from the blood.

[The effect of 1-p-bromphenyl-5-mercapto-1,2,3,4-tetrazole (Br FMT) on thyroid gland function in rats]

The effects of the novel potential thyrostatic agent 1-p-bromphenyl-5- mercapto-1,2,3,4-tetrazole (Br-FMT) on the serum levels of thyroxine, thyrotropic hormone (TSH), the content of cyclic adenosine monophosphate (cAMP) in the thyroid gland, the body weight and the weight of the thyroid gland in liver transaminases and the white blood picture in Wistar strain rats were investigated. The effect of Br-FMT was compared with the effect of the well-known thyrostatic agent and goitrogen ethylester of 3-methyl-2-thio-4-imidazoline-1- carboxylic acid, carbimazole (Spofa) and with the control group, which received placebo only. The drugs tested were administered to animals in the dose do 7.5 mumol/animal via a gastric tube for the period of one month. Br-FMT and carbimazole decreased the level of serum thyroxine in a statistically significant manner. The serum level of TSH was evidently decreased after Br-FMT; it was not changed after administration of carbimazole in the given dose. The content of cAMP in the thyroid gland was significantly increased only after carbimazole. The weight of the thyroid gland was not significantly changed in any group under study, though after carbimazole the mean value was higher by a quarter as compared with the control group. The body weight and white blood picture were not significantly changed in all groups under study. ALT and AST values were evidently lower after carbimazole and Br-FMT, most probably due to the hypothyroid state of the animals.(ABSTRACT TRUNCATED AT 250 WORDS)

[Comparison of the results of radioimmunologic and hemagglutination methods in the determination of antibodies against thyroglobulin and the effect of these antibodies on thyroglobulin serum levels]

The following methods have been introduced at our institute: labeling of human thyroglobulin (H-Tg) with the radioiodine 125I by the lactoperoxidase method, radioimmunologic method for serum H-Tg determination by means of rabbit antiserum to H-Tg prepared at our institute, and radioimmunologic method for the determination of antibodies to thyroglobulin. Sera from 15 patients with different thyropathies were examined by the given methods. In the first part of the work the quality of 125I labeled H-Tg was studied. The maximum binding by antiserum was found to be substantially decreased as early as two weeks following labeling, The second part of the study presents our first experience with comparing our RIA method and the hemagglutination method for TgAb determination. The results yielded by the two methods did not differ significantly. The level of serum H-Tg is falsely affected by the competition of TgAb autoantibodies with the first rabbit antibody to H-Tg at recipitation by means of the second antibody. It is therefore important to establish the titer of autoantibodies before actual serum H-Tg determination. This approach is of importance e.g. in following up patients with malignant goiter. The introduced methods are a contribution to diagnosis and management of patients with thyropathies.

Thyrotropin releasing hormone in the pancreas of newborn rats from streptozotocin-treated mothers

The effect of maternal diabetes (induced by i.p. injections of 40-50 mg/kg BW Streptozotocin on the day of mating) on TRH in the pancreas of newborn rats was studied. Determination of peptide alpha amidation activity and TRH precursor level on the day of birth revealed decreased biosynthesis of TRH resulting in profoundly (10 times) lower pancreatic TRH and TRH-OH concentrations in pups of diabetic rats. Pancreatic His-Pro-diketopiperazine (His-Pro-DKP) remained unaffected by maternal diabetes. The depression of pancreatic TRH was less profound 24 h later, and even elevated TRH was measured in the pancreas of pups of diabetic mothers on postnatal day 5. Short term postnatal starvation or nursing of intact pups by the diabetic foster mother did not affect pancreatic TRH. It could be postulated that postnatal TRH development in the rat pancreas is retarded by maternal diabetes, while His-Pro-DKP remains unaltered.

Thyroid hormone levels in cow maternal and fetal sera during last trimester of pregnancy

Thyroid hormone levels were studied in 51 paired pregnant cow and fetal calf serum samples (fetal age 7-9 months). Thyroxine and rT3 levels were substantially higher and those of T3 distinctly lower in calf fetuses as compared to respective mothers. An increase of T3 has been detected in calf sera at the fetal age 8 to 8.5 months. These results suggest some prenatal maturation of thyroxine metabolism in the calf.

Exchange transfusion in premature newborns: effect of maturity on thyrotropin and thyroxine responses

The effects of exchange transfusion on plasma T4 and TSH were studied in two groups of premature newborns to evaluate the effect of maturation on the reactivity of the pituitary-thyroid axis. In newborns with a birth weight between 1900-2500 g (gestational age 35.4 +/- 0.45 weeks) the responses of both hormones were essentially similar to those reported previously for mature newborns (a profound decrease during the procedure and an increase 24 h later). In a group of newborns with a birth weight below 1900 g (average 1673 +/- 55, gestational age 32.7 +/- 0.72 weeks), however, the secondary increase in plasma T4 at 24 h after the procedure was absent. At this time both T4 and TSH levels were significantly lower than in those in heavier newborns. It is concluded that the ability to respond to exchange transfusion by an increase in plasma thyroxine at 24 h after the procedure matures at the gestational age between 32 and 35 weeks.

Effects of sauna and glucose intake on TSH and thyroid hormone levels in plasma of euthyroid subjects

The effect of sauna on thyroid function parameters and its modification by glucose was studied in young euthyroid male volunteers. A 30-minute stay in sauna resulted in an increase in plasma TSH; the response was exaggerated if glycemia had been increased by oral glucose intake at the beginning of the experiment. Plasma rT3 also increased in sauna, this response was, however, blunted by the higher glycemia. TSH response to sauna was definitely present in young men (aged 20 to 25) and absent in middle-aged ones (50 to 55). To explore the mechanism of the effect of increased glycemia, TRH tests were performed and dopamine infusions were administered with and without glucose pretreatment. Increased glycemia did not affect TSH and T3 response to TRH in young volunteers; however, 90 minutes after the administration, plasma rT3 levels were significantly lower in glucose pretreated subjects than in those receiving TRH injections after water pretreatment. Simultaneous infusion of glucose prevented the inhibitory effect of dopamine infusion on plasma TSH. It was concluded that glucose directly modulates the effect of sauna on plasma TSH at a suprapituitary level, while the inhibiting effect of glucose on plasma rT3 response to sauna and TRH is probably mediated by the insulin effect on thyroid hormone metabolism.

Human milk does not degrade TRH

We have found previously that TRH is accumulated in rat milk in biologically active form. TRH was reported to be present in high concentrations in human milk too. These findings together with the absence of TRH degrading activity in plasma of newborns suggest a possible physiological role of the neurohormone coming from milk. We studied, therefore, TRH degrading activity of human milk. TRH incubated in vitro with 100 microliters human milk (4 days and 4 months after delivery) in 0.01 mol l-1 phosphate saline buffer (pH 7.6) with 1% gelatine (total volume 0.3 ml) at 37 degrees C was not degraded during 2 hours as revealed by specific RIA. The addition of the same amount of milk to adult human plasma did not affect intensive TRH degradation. We conclude that human milk does not contain TRH degrading enzymes nor their inhibitors.

Effect of breast-feeding on infant thyroid activity: 3 year follow up--longitudinal study

The effect of breast-feeding on serum thyroid hormones and TSH was studied in a longitudinal study from birth up to 3 years. T4 was found to be significantly higher in breast-fed than in weaned infants at the age of 4 and 6 months and so was rT3 at the age 4 months. The body weight of breast-fed girls at the age 4 and 6 months was lower than that of formula-fed ones. Breast-feeding at the age 9 months resulted in a decreased serum TSH. Serum T3 of infants weaned before the end of the first week of life was higher than in other groups of infants at the age of 10 weeks. Serum T4 of children 1-2-year-old correlated positively with the age at weaning, provided that they had been breast-fed at least for 60 days. Serum rT3 of 2-year-old children also correlated with the age of weaning. Serum TSH at the age of 3 years was higher in children who had been weaned during first 60 days of life than in those weaned later. It is concluded that breast-feeding possess some immediate effects on thyroid function parameters. Some effects were still detected at the age of 1-3 years.

Role of thyrotropin-releasing hormone in thyroid-stimulating hormone and growth hormone regulation during postnatal maturation in female Wistar rats

The role of endogenous thyrotropin-releasing hormone (TRH) in the control of pituitary thyroid-stimulating hormone (TSH) and growth hormone (GH) secretion was studied during postnatal maturation in female Wistar rats. Half of the sucklings in each litter was treated intraperitoneally with either specific rabbit antiserum against TRH or normal rabbit serum (0.1-0.3 ml according to age). All animals were decapitated after 2 h. The presence of anti-TRH activity was checked as a binding of labelled TRH with plasma of the experimental animals. Immunoneutralization of endogenous TRH resulted in a decrease of plasma TSH in 3- to 15-day-old female pups as compared to control littermates. No effect of TRH antibody injection was seen at the ages of 1, 21, 30 and 70 days despite the presence of excess antibody in the plasma. A profound effect of TRH antibody on plasma TSH was seen again at the age of 100 days. Plasma GH in the same animals exhibited a paradoxical increase after TRH immunoneutralization at the age of 5 and 8 days, a decrease was found at the age of 21 days. It was concluded that hypothalamic TRH control of TSH secretion matures early in Wistar rats. Hypothalamic secretion of TRH at the ages of 1, 21, 30, and 70 days is low and(or) its role in TSH regulation is masked by other regulating factors. TRH may play a dual role in the regulation of GH secretion during the postnatal period.

TRH analogue with C-terminal thioamide group: rapid degradation by plasma and its biological effects

L-pyroglutamyl-L-histidyl-L-proline thioamide--([Prot3]TRH), a new TRH analogue, has been previously found to have the same binding affinity to adenopituitary receptors as well as TSH and alpha-MSH releasing activities as native TRH. In this paper we report also the same time course of TSH response after i.p. injection of this compound (10 micrograms kg-1) to rats. Binding affinity to specific receptors in rat amygdala, cortex (frontal lobes), hypothalamus, striatum (order according to decreasing affinity) of both peptides was also similar. In contrast to TRH, however, [Prot3]TRH in doses 0.5 and 5 mg kg-1 i.p. did not affect sleeping time and breathing frequency in the rats during barbiturate anaesthesia. Surprisingly, human plasma degraded the new analogue much faster (T1/2 8.5 min) than native TRH (T1/2 30 min). [Prot3]TRH was also degraded faster in plasma of adult rats. Plasma of 6-day-old rat pups failed to degrade both peptides. It was concluded that the substitution of proline amide, for proline thioamide group in TRH molecule did not change binding affinity to receptors in the central nervous system, but decreased biological effectiveness in CNS and substantially decreased the resistance to degradation in human and rat plasma.

Maturation of the inhibitory response of growth hormone secretion to ether stress in postnatal rat

To study the maturation of inhibitory influences on growth hormone (GH) secretion the effect of ether stress on plasma GH levels was studied during postnatal ontogenesis in female rats. Ether stress did not affect plasma GH levels in 1-day-old pups. A distinct decrease of plasma GH was found in 3- and 9-day-old pups, and the response was prevented by treatment of 3-day-old animals with somatostatin antiserum. No effect of ether stress on plasma GH was noted in 12-, 15-, 18- and 21-day-old rats. Treatment of intact 12-day-old pups with the somatostatin antiserum increased plasma GH level under basal conditions. The inhibitory effect of ether stress on plasma GH was noted again at the age 30 days and in adult animals. It is concluded that the hypothalamus of 3-day-old rats is able to release enough somatostatin to inhibit GH secretion after stress. At the period 12-18 days a phase of pituitary refractoriness was noted: ether stress as well as TRH injection (our previous observation) fail to affect plasma GH in female pups, probably due to high somatostatin secretion under basal conditions and (or) low capacity of pituitary to release GH. It is suggested that regulation of GH secretion is not mature until after the 21st day of life.