Pattern Of GH Secretion Research Articles

A study on the secretory pattern of GH, TSH, LH and FSH in neonates. II) Changes in serum GH, TSH, LH and FSH levels under the condition of various kinds of loads (author's transl)

A study on the secretory pattern of GH, TSH, LH and FSH in neonates. II) Changes in serum GH, TSH, LH and FSH levels under the condition of various kinds of loads (author's transl)

EVALUATION OF THE RESULTS OF TRANS‐SPHENOIDAL SURGERY IN ACROMEGALY BY ASSESSMENT OF THE GROWTH HORMONE RESPONSE TO THYROTROPHIN‐RELEASING HORMONE

Eighteen acromegalic patients GH-responsive to TRH were reinvestigated following trans-sphenoidal surgery and radiotherapy. Basal serum GH decreased below 10 microgram/1 in thirteen cases; nine of them became GH-unresponsive to TRH 1 month after operation, and another one following conventional pituitary irradiation. Four of these ten patients also showed a normal GH response to L-Dopa after treatment, and five responded normally to insulin-induced hypoglycaemia; two patients had a normal GH secretory pattern after both these stimuli. No recurrences were observed over a follow-up period of 15-80 months among the ten patients who became GH-unresponsive to TRH following operation, while one of the three subjects still responsive to TRH in spite of normalized basal serum GH concentration relapsed 10 months after surgery. Three patients with normalized TRH test following operation were repeatedly reinvestigated over a 3-6 years period and always found unresponsive. The present study shows that the 'paradoxical' GH responses to TRH and L-Dopa frequently disappear after surgery, that complete normalization of GH secretory pattern may rarely be attained, and that the disappearance of GH response to TRH probably indicates satisfactory treatment of acromegaly. These data suggest that the 'paradoxical' GH responses frequently found in acromegaly are dependent on the adenoma per se and not on hypothalamic dysfunction.

Somatostatin: A Physiological Role in the Regulation of Growth Hormone Secretion in the Adolescent Male Baboon*

Insulin and GH secretion patterns were surveyed in four adolescent male baboons before and after active immunization against cyclic somatostatin. Before immunization, an ultradian GH rhythm with an interpeak interval of 4.1 ± 0.33 (SE) h was observed during a 12-h daylight sampling period. The rhythm was characterized by 2- to 12-fold increases in serum GH concentration; each burst was maintained over 3.15 ± 0.25 h. After immunization, baseline serum GH concentration was increased and episodic bursts of GH secretion were markedly diminished. The total integrated areas over 12 h did not differ between the control and postimmunization studies. A comparison of the autocorrelation analyses of GH secretion before and after active immunization revealed that the immunization procedure effected a disruption of the synchronous ultradian GH rhythm observed before treatment. Basal plasma insulin and glucose concentrations were observed in overnight-fasted subjects. There was no apparent effect of the immunization pr...

302 PROVOCATIVE AND INTEGRATED CONCENTRATIONS OF GROWTH HORMONE (GH) IN DIVERSE GROWTH DISORDERS

Since provocative tests for GH release may not reflect normal GH secretory patterns, we studied 18 children with diverse growth disorders, age 7-18 yrs, by two standard stimuli (L-Dopa, arginine,insulin-induced hypoglycemia) and by continuous blood withdrawal (collected hourly) for 12 and 24 hr integrated GH concentrations (ICGH). Tests were started at 0800 hr; 12 hr ICGH was calculated for 1800-0600 hrs. Six patients with normal stimulation tests (peak > 10 ng/ml) had 12 hr ICGH = 5.2 ± 2.6 ng/ml (mean ± S.D.; range 2.5-9.1); two boys with delayed adolescence had no hourly peak > 10 ng/ml. Five patients with borderline stimulation tests (peak GH 7-10 ng/ml) had 12 hr ICGH 4.0 ± 2.3 (range 1.5-6.7); in 3/5, the peak integrated hourly levels were low: 4.5, 4.7, 8.7. Seven patients with low stimulation tests (peak < 7 ng/ml) had 12 hr ICGH 0.75 ± 0.6 ng/ml (range 0.18-1.96); all had hourly peak ICGH < 3.5 ng/ml and 6/7 had clinical evidence of GH deficiency. Patients with delayed puberty had borderline or normal provocative GH; however, 4/5 had low 12 hr ICGH and hourly peaks. There were highly significant correlations between ICGH peak, 12 hr ICGH and peak provocative GH (p < 0.001). In all groups, 12 hr ICGH correlated with 24 hr ICGH (p < 0.001). With the exception of one child with obesity, growth velocities correlated more closely with ICGH than with provocative GH. Constant withdrawal may be helpful particularly in patients with borderline provocative tests and/or sexual immaturity.

Serum growth hormone levels in schizophrenic patients during sleep.

Ten schizophrenic and five epileptic patients under antipsychotic drug treatment were studied to evaluate sleep-related GH secretion. Four of the schizophrenic patients had a high secretion peak of GH (range 15.2 to 38.0 ng/ml), four had a moderate peak (range 5.8--8.3 ng/ml), while two had no increase in GH secretion during sleep (range 0.5--1.0 ng/mg). Four of the five epileptic patients had a moderately increased secretion (range 5.8--9.2 ng/ml) and one had no increase in GH secretion during sleep. Thus, the GH secretory pattern varied with the patient as in known to be also with healthy individuals. However, no clear disturbances were noted in sleep-related GH secretion in schizophrenic patients receiving antipsychotic drug treatment, when compared e.g. to non-schizophrenic, epileptic patients under a same kind of drug treatment.

Ultradian growth hormone rhythm in the rat: effects of feeding, hyperglycemia, and insulin-induced hypoglycemia.

Temporal patterns of plasma GH, immunoreactive insulin (IRI), and glucose were defined by obtaining serial blood samples from freely-moving male rats bearing chronic intracardiac venous cannulae. Blood was withdrawn every 15 min for periods of 6 h. Plasma GH and IRI were determined by radioimmunoassay. The typical ultradian rhythm of GH secretion was evident in each undisturbed animal (peaks greater than 200 ng/ml; troughs less than 1 ng/ml; mean period: 3.40 +/-0.08 h). Basal plasma IRI and glucose levels fluctuated minimally. There was no significant correlation between plasma GH and IRI, GH and glucose, or IRI and glucose levels in unfed rats. The rhythmic GH secretory patterns of feeding animals (mean period: 3.12 +/-0.16 h; peaks greater than 200 ng/ml; troughs less than 1 ng/ml) were similar to those of non-feeding animals (mean period: 3.34 +/-0.15 h; peaks greater than 200 ng/ml; troughs less than 1 ng/ml) despite large fluctuations in plasma IRI levels and a wide variation in the number and size of the meals taken. No consistent relation was observed between the ingestion of meals and the bursts of GH secretion. The mean period of the GH rhythm was not significantly altered by hyperglycemia (mean period; 3.25 +/- 0.08 h), although the amplitude of the pulses of half of the hyperglycemic rats was markedly depressed. Insulin-induced hypoglycemia caused a significant depression in the amplitude of the GH pulses; however, the pattern of this response was not consistent. Despite wide variability in the GH response, the magnitude and time course of recovery of the plasma glucose levels was similar in all animals. These results suggest that GH secretion in the rat is regulated primarily by an endogenous ultradian rhythm which is not dependent on changes in plasma glucose or IRI levels, and continues to function independently of feeding behavior. It is unlikely that GH is an important physiologic regulator of glucose homeostasis in this species.

Evidence for an endogenous ultradian rhythm governing growth hormone secretion in the rat.

Sequential blood samples were obtained from undisturbed freely-behaving male rats bearing chronic intracardiac venous cannulae. Blood was withdrawn every 15 min for periods of 4-24 h; plasma was separated, and saline-resuspended red cells were reinjected. Plasma GH was determined by radioimmunoassay. Pulsatile GH secretion was evident in each animal with most peak values greater than 200 ng/ml and most trough values less than ng/ml. The GH secretory episodes occurred at approximately 3 h intervals, and this rhythmic pattern of GH secretion persisted unchanged across all phases of a 12-h light-dark (L-D) cycle. Seven major episodes of GH secretion were observed during a single 24-h period. The mean period, or time interval between episodes, in 24 animals was 3.32 +/- 0.07 (SEM)h. The timing of the pulses with respect to the L-D cycle was similar in most animals, indicating that the rhythm may be entrained to the L-D cycle. The role of environmental lighting was further assessed in 14 animals exposed to constant light for 7 weeks. The results show that the basic rhythm was unchanged (mean period 3.18 +/- 0.06 h, peaks greater than 200 ng/ml, troughs less than 1 ng/ml), although entrainment to time of day was not evident. Subsequent exposure to the 12-h L-D cycle resulted in reversion to an entrained rhythm. These results suggest 1) that GH secretion in the rat is governed by an endogenous ultradian rhythm, with a periodicity of approximately 3.3 h, and 2) that the alternation of light and darkness probably serves as a Zeitgeber which sets the biological "clock" for GH secretion, but is not necessary for maintenance of the basic rhythm.