Difficulties and controversies still exist in the diagnosis of small (3-5 mm) prolactinomas (micro-PRL-omas). In the present study serum prolactin (PRL) was assayed in 4199 women aged 14-43 years belonging to 4 groups: A: 753 women with normal cycles (NC) and infertility (control group), B: 2523 with menstrual disorders, C: 519 with NC and hirsutism, D: 404 with galactorrhoea. The distribution of PRL values from 1 to 30 ng/ml was almost similar in the subjects of group A, B and C. Within this range the vast majority of subjects (91%, 92.2% and 88% respectively in these 3 groups and 83% in group D) had PRL levels from 1 to 15 ng/ml and together with the proportion of subjects with PRL values 16 to 20 ng/ml they included 96.7% of the entire mixed population. A proportion of scattered outlying PRL values above 30 ng/ml was found in each group (A = 2%, B = 3%, C = 1% and D = 28.7%) and in this subset 117 prolactinomas (PRL-omas) were found, 19 (23%) in the 83 subjects with PRL levels 31-49 ng/ml and 98 (75.3%) in the 130 subjects with PRL values greater than or equal to 50 ng/ml. Of the 117 PRL-omas 9 were bigger than 10 mm and 4 had a size from 6 to 9 mm. In the remaining 104 the size was presumed from direct or indirect radiological evidence to be 3-5 mm.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of the growth hormone (GH) secretory dynamics of children with normal and idiopathic short stature (ISS) have revealed that the regulation of the GH-somatomedin (GHS) axis can differ significantly among normal individuals. Information on the GH secretion in idiopathic tall stature (ITS) is scarce. We previously showed that the GH response to stimulation with GH-releasing hormone (GHRH) in male, late adolescents and young adults with ITS is significantly greater than that of their sex and age-matched controls of average height. In the present study, we studied the 24-hour (hr) GH, insulin-like growth factor-I and -II (IGF-I and -II), prolactin (PRL) and thyroid-stimulating hormone (TSH) secretion by every 30 minutes (min) sampling in 12 young, healthy male Greek army recruits. Group I [n = 6, age 22 + 1.4 years (y.), mean + standard deviation (SD)] had a height of 198.5 + 4.2cm, at least 3 SD's above the mean of the Greek male population. Group II (n = 6, age 20.5 + 1.05 y.) had a height of 169.2 + 3.4cm, within 2SD's of the normal mean. Serum IGF-I levels were determined in both unextracted and extracted samples. Our results indicated that the number of secretory bursts and the circadian panel of GH, IGF-I and -II, PRL and TSH were similar in the two groups. Both the amplitude of the secretory GH peaks (5.08 + 3.07 vs. 3.3 + 0.8 ng/ml, p = 0.19,) and the area under the curve (AUC) of the 24-hour GH secretion (9.8 + 5.5 vs. 6.6 + 1.3 ng/ml/hr, p = 0.2) were higher in group I than in group II, but the difference was not significant. A significant nocturnal increase of both IGF-I and -II levels was found only in extracted human plasma (p < 0.001), whereas measurements of IGF-I in unextracted samples failed to reveal circadian variation (p < 0.1). We conclude that no significant differences were found in this pilot study of the neurosecretory regulation of the GHS axis between individuals of tall and normal stature. A tendency for greater amount of GH secretion per secretory peak was found in persons with tall stature; however, this finding needs to be confirmed in a larger study. IGF-I and -II levels had a significant circadian variation with a large nocturnal surge, when measured in extracted plasma. The latter, might be explained by circadian variation of the circulating IGF-binding proteins and its detection appears to be method of extraction-dependent.

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The importance of growth hormone secretion to the growth of an individual raises the question of the role that the secretory capacity of this hormone may play in defining the variations of height within the population. To investigate this problem we studied the response of GH to GHRH in 20 normal tall (mean +/- SD height 190.8 +/- 2.4 cm, range 187-196 cm) adult males of the third decade and in 17 age-matched controls of average height (mean +/- SD height 173.8 +/- 1.6 cm, range 171-177 cm). Synthetic GHRH (1-29) NH2 (Kabi, Vitrum, Sweden) was administered at 0800 h after an overnight fast and blood was drawn for GH assay. In the tall subjects basal GH concentrations at -15 and 0 min were not significantly different from those of the controls. However, the tendency to higher basal GH levels and spontaneous peaks was evident in tall individuals. Only three basal GH values were below 1 micrograms/l (0.8-0.9 micrograms/l; 1 microgram/l = 2mU/l) in the tall individuals while 24 of 33 basal GH values in the controls ranged between 0.25 and 0.87 micrograms/l. At +15 and +30 min after GHRH the rise in GH was significantly greater in the tall subjects. Moreover, the integrated area under the response curves was significantly greater in the tall subjects than the controls (P less than 0.01). No differences in the mean serum testosterone and prolactin levels were found in the two groups. It is postulated that if this enhanced pituitary responsiveness is constant and chronic in tall individuals a definite relation of their stature to the GH secretion is to be anticipated.

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