Ontogeny of circadian rhythmicity for melatonin, serotonin, and N-acetylserotonin in humans

The serum concentration of melatonin, serotonin, and N-acetylserotonin were measured by RIA procedures in 28 infants aged 1 week to 9 months. Blood specimens were obtained at 12:00 hr and 24:00 hr. A day-night difference in serum serotonin was present immediately after birth. A significant (P less than 0.001) decrease in serum serotonin concentrations at 12:00 hr and 24:00 hr was observed from the first month of age to the third to ninth month of age. A significant (P less than 0.05) difference in day-night N-acetylserotonin concentration is first seen at age 1-3 months. Serum melatonin concentrations, though detectable, did not show any day-night difference at birth. Melatonin concentrations progressively increased up to the third month of age, and a significant (P less than 0.01) day-night difference appeared thereafter. The results indicate that in humans the circadian organization for serotonin already exists at birth, and the circadian melatonin rhythm develops after birth.

Circadian rhythms in serum melatonin from infancy to adolescence

The circadian rhythm of circulating melatonin was determined in 38 children, aged 1-18 yr. Serum melatonin concentrations at 2400 and 0300 h in children aged 1-5 yr were significantly (P less than 0.001) higher than those in older children [6-10 yr, puberty stage 1 (P1)]. Nocturnal melatonin levels also were significantly (P less than 0.01) higher in P1 subjects than in P2 subjects aged 9-12 yr. A further small decline was found from P2 to P4/P5 (P less than 0.05). Thus, the decline in the nocturnal melatonin surge is not exclusively related to pubertal development, but begins in infancy.

Heterogeneity of rat FSH by chromatofocusing: studies on in-vitro bioactivity of pituitary FSH forms and effect of neuraminidase treatment

This study concerned the resolution of rat pituitary FSH utilizing chromatofocusing. Among the 11 components resolved and positively identified, ten had apparent isoelectric points (pI) between 3.1 and 5.1. Approximately 1% of pituitary FSH eluted at pH 9.4. Treatment with varying amounts of neuraminidase followed by refocusing generated FSH components of higher pI values. Treatment with other glycosidases did not alter the elution characteristics in chromatofocusing, while exclusion chromatography established an inverse relationship between apparent molecular weight and pI. Dose-response curves of various FSH components and of the reference preparation in the current radioimmunoassay system were parallel to each other. A study of their in-vitro bioactivity, utilizing granulosa cells which produce a plasminogen activator due to FSH in a dose-dependent manner, provided the following evidence: increased acidity of the components led to an increase of maximum response and an increase of the dose necessary for half-maximum response. Considering the observed alterations in the heterogeneity of FSH with changing physiological states of the animal, it is concluded that qualitative changes of the FSH molecule are perhaps involved in a modulatory role in the biopotencies of the hormone.

Heterogeneity of rat FSH by chromatofocusing: studies on serum FSH, hormone released in vitro and metabolic clearance rates of its various forms

Rat pituitary FSH was fractionated by chromatofocusing between pH 6 and 3. Ten components were resolved having apparent isoelectric points between 3.1 and 5.1. A comparative study of pituitary FSH and FSH secreted in vitro by quartered pituitary glands in the presence and in the absence of gonadotrophin-releasing hormone (GnRH) revealed similar patterns of charged species of intracellular and released FSH. Although GnRH increased FSH secretion about fourfold, no influence on the pattern of charged species was observed. Utilizing exclusion chromatography and chromatofocusing, pituitary FSH was compared to serum FSH which had been extracted by immuno-affinity chromatography. The results demonstrate for serum FSH a larger molecular size and a relative shift to more acidic components. Metabolic clearance rates of eight FSH components separated by chromatofocusing were measured in adult male rats. Half-lives varied between 13 min and several hours. A correlation existed between decrease of isoelectric points and decrease of metabolic clearance rates. These findings suggest that all hypophysial FSH components are secreted into the circulation at similar rates and the more acidic FSH components which appear to contain increased sialic acid, have a longer circulatory half-life and are more abundant in serum. It is concluded that sialylation may be involved in modulating serum FSH levels.

Evidence for modulation of melatonin secretion in men with benign and malignant tumors of the prostate: relationship with the pituitary hormones

The serum levels of the pineal hormone melatonin were determined by radioimmunoassay (RIA) in 4-h intervals throughout a 24-h period in elderly men with different types of prostate tumors: benign prostatic hyperplasia (BPH, n = 13), incidental carcinoma (PCi, n = 5), and nonmetastasizing carcinoma (PC, n = 9), as well as in young men (YM, n = 10). Simultaneously, the pituitary hormones prolactin, growth hormone, luteinizing hormone and follicle-stimulating hormone were measured by RIA. All subjects were untreated and free of serious complaints, and they stayed in the same environment. The data were analyzed by the population mean-cosinor method, and linear correlation coefficients between the five hormones were calculated for each group. Melatonin showed significant circadian rhythms in young men and patients with BPH and PCi but not in patients with PC. Twenty-four-hour mean concentration (mesor) and amplitude were significantly increased in patients with PCi as compared to patients with PC. Prolactin showed significant circadian rhythms in young men and in patients with BPH, whereas patients with PCi and PC appeared to have ultradian variations. Growth hormone did not show significant rhythms in any of the groups; the mesors were elevated in all tumor groups as compared to young men. Gonadotropin mesors were elevated in all tumor patients as compared to young men; rhythms were not detected. Carcinoma patients showed different interhormonal correlations than all other groups. These results indicate that modulation of melatonin secretion, accompanied by changes in the pituitary hormone levels, may be related to development and growth of prostate cancer.

Studies on the age-dependent nature of the response to LHRH given via different routes

The effect of synthetic LHRH on circulating levels of LH and FSH in three groups of male rats, prepubertal, pubertal and adult, was compared after intravenous, intraperitoneal and subcutaneous administration. In two further series of experiments, infusion of LHRH over 120 min or two i.v. bolus injection at an interval of 60 min were carried out. Blood was collected from individual animals at each time-point before and after LHRH administration. The results indicate that the responsiveness of LH and FSH to LHRH was dependent not only on the routes of injection but also on the maturation of the animals. The infusion of LHRH induced the greatest response of LH and FSH in all the groups of animals. The pubertal group demonstrated greater responsiveness of LH than the other two groups. The second bolus injection of LHRH after 60 min elicited a much greater response for both gonadotropins in all age groups than that following the first injection. This indicates the existence of a priming effect of LHRH on LH and FSH; this effect was observed in all groups irrespective of their maturational status.

Hormones and human milk

The presence of several hormones in milk occurring either by passive diffusion or by active concentrating mechanism from blood can be of great concern to the neonate. According to Fulkerson [1979] when the clearance rates of the hormones out of blood is considered, this worry is unwarranted. Concerning the steroids, when their levels have been monitored in milk after lactogenesis, the worry for the baby seems to be unfounded. But with the new finding of high level of LH-RH in milk whose concentration far exceeds that of blood, care should be taken to examine in the neonates whether the levels of LH and FSH become disproportionately high and induce the secretion of gonadal steroids at a higher level.

Role of the pineal gland in the regulation of prostatic androgen receptors in pubertal and mature rats

The effects of exposure to continuous light, continuous darkness, and administration of melatonin on prostatic androgen receptors in relation to pubertal development in rats were examined. Darkness produced dissimilar results between the pubertal and adult groups. Whereas the prostate weight in the pubertal group remained unaltered, it increased in the adult group. In the pubertal group exposed to darkness, plasma melatonin increased significantly, and androgen receptors declined, whereas in the adult group these receptors rose significantly with a simultaneous increment of melatonin concentration in plasma. Exposure to continuous light did not produce any effective alterations in the parameters examined. The afternoon melatonin administration showed trends similar to those seen in animals exposed to darkness. The results indicate that exposure to darkness or administration of melatonin both have age-dependent effects on prostatic androgen receptors. Exposure to darkness may interfere with the process of sexual maturation in the pubertal animal as a result of increased melatonin production.

Effect of tetrahydrocannabinols on pubertal body weight spurt and sex hormones in developing male rats

Chronic administration of delta 8- and delta 9-tetrahydrocannabinols (4 mg/kg b.wt. i.p.) to sexually developing male rats every alternate day from age day 16 to age day 87 resulted in a significant decrease in pubertal growth spurts, especially the second peak. Endogenous testosterone, dihydrotestosterone, LH and FSH concentration in blood declined significantly from those of the control animals. When the drugs were withdrawn at mid-puberty (age day 40) the "catch-up" phenomenon in body growth weas evident although testosterone level continued to be suppressed but dihydrotestosterone level recovered. Withdrawal of the drugs resulted in better recovery in LH level compared to that of FSH. Administration of LH-RH to the animals receiving drugs until day 87 resulted in significantly (P less than 0.001) lower levels of gonadotropins than those in the control animals. The inhibition in delta 9-THC-treated animals was more severe than in delta 8-THC-treated ones. When the drug was withdrawn, delta 8-THC-treated animals responded to LH-RH stimulation better than did those treated with delta 9-THC. These findings suggest that the tetrahydrocannabinols perhaps mainly affect pituitary function.

Osteoinductivity of partially decalcified alloimplants in healing of large osteoperiosteal defects

About 3.5 cm osteoperiosteal circumferential gaps in rabbit ulnae were bridged by partially decalcified (by 0.6 M HCl) allogenic implants, 8-12 weeks after implantation complete bridging of the gap by new bone formation and union at host-graft junctions was observed in 97.2 per cent of the experiments. Instant permeability and the powerful osteo-inductive potential of the implant coupled with some degree of mechanical stability provided by partial decalcification ensured successful bone formation in almost all the experiments. It is suggested that partially decalcified allogenic bone matrix preserved in 70 per cent ethanol may be a reasonably good substitute for autologous bone graft.

Bridging large bone defects with a xenograft composited with autologous bone marrow. An experimental study

We have investigated the role of defatted, decalcified xenogenic bone implants composited by impregnation with fresh autologous marrow in bridging large cortical defects. Diaphyseal cortical implants were obtained from orthopaedic operations on humans and from guinea pigs and prepared by treatment with acetone, 0.6 M HCl and ethanol. The composited graft was used to bridge a 3 cm defect in the diaphysis of the ulna of rabbits. Periodic investigations were made clinically, radiographically and histologically and by tetracycline, fluorescence studies up to 20 weeks. Abundant new bone formation was observed in 85.7% of composited human xeno-autografts and in 83.3% of composited guinea pig xeno-autografts. New bone formation was seen in 13.3% of noncomposited xeno-implants. No appreciable antigenicity was observed either clinically or histologically in the grafts. The high degree of success obtained justifies further studies on implants composited by fresh autologous marrow and offers hope for the enhancement of new bone formation clinically, particularly in reconstructive operations for significant skeletal defects. We feel that the osteo-inductive potential of autologous marrow was responsible for the healing of the defects aided by the better internal milieu provided by defatted decalcified xeno implant.

Amniotic fluid levels of 17 alpha-hydroxyprogesterone during human pregnancy: pre-natal diagnosis of congenital adrenal hyperplasia due to 21-hydroxylase deficiency

Levels of 17 alpha-hydroxyprogesterone were estimated by radioimmunoassay in 174 amniotic fluid specimens obtained from 162 normal pregnancies of 16-20 weeks gestation. Another 18 specimens from 11 normal pregnancies between 25-42 weeks gestation and 7 specimens from 7 women who each previously had given birth to a child affected with CAH were also studied. There was no sex difference in AF 17 alpha-OH-progesterone levels, nor any significant downward trend in concentrations throughout the observed gestation period. Among the 7 subjects with previous history of CAH offsprings, 4 demonstrated normal levels of AF 17 alpha-OH-progesterone and 3 significantly higher values. HLA-typing of the cultivated amniotic cells confirmed these 4 cases to be heterozygous for 21-hydroxylase deficiency. The three subjects with high AF 17 alpha-OH-progesterone levels delivered babies affected with CAH, although HLA-typing in one case was non-conclusive. The failure of HLA-typing in 1 case for a confirmatory diagnosis indicates that the prenatal diagnosis of CAH must continue to rest on joint endocrinological and genetical investigations.

Effect of human chorionic gonadotropin on the plasma levels of testosterone, estradiol, sex hormone binding globuline and free testosterone in Klinefelter syndrome

Preliminary experiments showed that a course of 3 X 5000 IU Human Chorionic Gonadotropin (HCG) every alternate day in 5 patients with Klinefelter Syndrome caused increment in the circulating levels of testosterone, estradiol, and Sex Hormone Binding Globuline (SHBG). The levels of free testosterone, however, declined in 3 subjects and recorded no change in the remaining two. Estradiol/testosterone ratio on day 0 showed high correlation (r = 0.853) with augmented SHBG. It has been postulated that higher amount of SHBG is perhaps potentiating a reduction in the bioavailability of testosterone.

Responsiveness of cortisol and dehydroepiandrosterone to ACTH in children

In a total of 101 children, the dehydroepiandrosterone (DHA) and cortisol (F) levels were measured before and after ACTH (Synacten) administration. F responsiveness was unchanged during development, while DHA responsiveness in healthy children was highest during adrenarche. In hypopituitary patients DHA levels were lower than in the controls, but responsiveness to ACTH showed similar changes during development. Children with Turner's syndrome and hypergonadotrophic males had the response in elevated DHA levels while ACTH-induced DHA response related to bone-age matched controls. We conclude that regulation of adrenal androgens is mediated by both ACTH and another hypothalamo-pituitary hormone, perhaps independent of gonadal activation, but requiring gonadal integrity.

The age of menarche in classical India

Data from the writings of Indian legislators during the period between ca. 500 B.C. and A.D. 500 have been used to study menarcheal age among girls born in classical India. As these legislators were concerned mainly with the upper-caste population, it can be presumed that the recordings obtained are only from upper-caste Hindu girls. Throughout the period the age at menarche was about 12 years. A number of legislators considered the best age for conception to be around 16. When these data are compared with those obtained from classical Greece and Rome, the Indian age is found to be about 1-2 years earlier. Comparison of the data from the 19th century and present-day India reveals that the older data are about 0.8-2.2 years earlier when various areas are considered. These results contrast with the downward trend for the age at menarche seen in the industrialized countries during this century.

Effect of morphogenesis on the infectivity of tissue

A technique was standardised to develop callus cultures from leaf tissues of tobacco plants infected with CPO strain of tobacco mosaic virus. These leaf callus cultures had a higher virus titre than the callus cultures developed from other explants such as stem, as evidenced by bioassay on local lesion hosts. Morphogenetic dedifferentiation of callus culture influenced the virus titre of the cultured tissues. Caulogenic dedifferentiation of the callus culture induced higher virus titre than rhizogenic dedifferentiation. In the non-differentiated callus cultures, however, the introduction of histogenesis, as evidenced by the compact growth, did not affect the virus titre. The formation of chlorophyll in the callus culture cells also did not change the infectivity of the tissue and thereby the virus titre.

Data on linkage relations between GLO and 21-hydroxylase

Linkage between GLO and 21-hydroxylase was investigated in 11 families with 24 children. Positive lod score values with a maximum of +1.618 at theta = 0.05 indicate close linkage between these marker loci.

Clinicobacteriological Study of Acne Vulgaris

The aetiological relationship Propionibacterium acnes in acne vulgaris has been suggested. A clinicobacteriological study in 45 patients suffering from acne vulgaris was conducted for the first time in Indian patients. P acnes could be isolated from 18 (40.0%) and other propionibacterium species from 9 (20.0%) of the 45 patients studied. No correlation of culture positivity with the sex of the patient or duration and grade of the disease could be established, P acnes antibodies were, tested for in 33 and 20 patients sera by agglutination and immunodiffusion tests respectively. Immunodiffusion test was positive in 5 (25 %) of the 33-patients and in only 1 (9.9%) of the 11 controls studied. The difference in the incidence of P acnes agglutinating antibodies in patients versus control was statistically significant (p = < 0.001).

Age related changes in pituitary responsiveness to luteinizing hormone-releasing hormone in the male rat

Changes in pituitary and serum concentrations of LH and FSH, determined by radioimmunoassay, were studied after administration of LH-RH to intact male rats of various ages. Although injection of LH-RH resulted in a depletion of pituitary LH and FSH in almost all age groups, thereby increasing the serum levels of these hormones, the magnitude and time course of the effects varied. Serum LH in the prepubertal and pubertal rats was maximal at 10 min after LH-RH injection, whereas the mature animals showed maximal increase only after 30 min. Peak serum concentrations of FSH found at 10 min in the prepubertal animals, but between 30 and 60 min in the pubertal and adult animals. At 35 days of age, significant pituitary depletion of LH and FSH occurred.

Hypothalamic control of the mammalian sexual maturation

The attainment of sexual maturity is a complex process which requires maturation and interaction not only of gonads and reproductive tract but also of the pituitary and essentially of the neuroendocrine mechanisms which ultimately control gonadotropin secretion. One of the more attractive hypotheses of the sexual maturation presumes the existence of the sensitivity threshold of the regulating system to the negative feedback signal, which differentiates immaturity from maturity. As the subject matures this declines. In an attempt to examine further the maturational alterations of the male hypothalamo-pituitary-gonadal axis, investigations were carried out with regard to simultaneous changes of blood LH, FSH, testosterone and dihydrotestosterone levels during the course of 24 hr; augmentation of pituitary and blood LH and FSH concentrations under the stimulus of LH-RH as a function of time and age; synthesis and release of LH and FSH in the testosterone-blocked animals at various stages of sexual maturation; and in vitro biotransformation of testosterone to its 5 alpha-reduced metabolites by the pituitaries as a function of age. Evidence from the experimental data could be interpreted as a decrement of the feedback set-points during sexual maturatio as reflected by the transition of the responses obtained under various experimental signals. In parallel to these observations, new evidence was presented regarding not only quantitative but qualitative changes in the pituitary gonadotropins as response to the negative and positive feedback signals. This leads to new thinking with regard to the hypothesis of differential sensitivity.

Plasma levels of 5alpha-androstane-3alpha,17beta-diol in boys during adolescent growth

A radioimmunoassay using as antibody against testosterone-3-carboxymethyloxime-BSA is described for the measurement of androstanediol (5alpha-androstane-3alpha,17beta-diol) in human plasma. Sephadex LH 20-column chromatography was used to separate other steroids croos-reaching with the antibody from androstanediol. The sensitivity of the assay was 7 pg and the recovery of labelled androstanediol was 65.1%. The intra-assay coefficient of variation was 9.9%. The existence of 5alpha-androstane-3alpha,17beta-diol in the androstanediol fraction could be demonstrated by gas chromatography and mass spectrometry (GC-MS). Plasma concentration of this substance was measured in 53 normally developing pre-pubertal and pubertal boys and in 13 adult men. The mean concentrations significantly rose from puberty stage 1 to 2, and stage 2 to 3. Although there was no significant difference between the plasma concentrations at stages 3 and 4, an increment from stage 4 and 5 was highly significant. Levels in adult males were significantly higher than those in the stage 5 of normal puberty.

Plasma testosterone in prepubertal cryptorchid boys under long-term HCG therapy

Plasma testosterone concentrations were determined before and after 6 weeks of human chorionic gonadotropin treatment in 36 prepubertal boys with bilateral or unilateral cryptorchidism. Mean +/- SD basal and post-treatment values (ng/100 ml) in the bilateral group were: treatment successful (n = 14): 32 +/- 19 and 302 +/- 49, treatment unsuccessful (n = 12): 20 +/- 15 and 176 +/- 73. The figures for the unilateral group were: treatment successful (n = 6): 23 +/- 9 and 244 +/- 41, treatment unsuccessful (n = 5): 22 +/- 11 and 264 +/- 102. In the bilateral group significant differences in the T response emerged when successfully treated boys were compared to unsuccessfully treated ones. It is concluded that Leydig cell function may be impaired in some cases of cryptorchidism.

Levels of luteinizing hormone, follicle-stimulating hormone, testosterone and dihydrotestosterone in the circulation of sexually maturing intact male rats and after orchidectomy and experimental bilateral cryptorchidism

Plasma concentrations of LH, FSH, testosterone and dihydrotestosterone (DHT) have been measured in normal sexually maturing male rats from the age of 16-90 days. Between 16 and 25 days plasma testosterone levels were low, but rose suddenly on day 26. A similar increment occurred at the same time in plasma DHT levels, but this steroid reached its peak concentration later than testosterone. Plasma LH levels rose steadily from day 25 onwards, reaching their highest values on day 30. A marked increase in FSH levels was found on day 16, and a peak was reached on day 33 followed by a decline to a level characteristic of the adult. In addition, plasma levels of all these hormones were estimated in the male animals at various stages of development after orchidectomy and cryptorchidism. Four days after operation, the plasma levels of LH and FSH in the orchidectomized animals reached higher levels than those found in the intact animals, indicating the existence of a dynamic feedback relationship before puberty between gonadal steroids and pituitary gonadotrophic secretion. However, results from the experimental bilaterally cryptochid animals, suggested that the gonadal steriod-gonadotrophic feedback relationship could not be the only factor initiating puberty.

Urinary androgen response of 8 girls with precocious puberty given cyproterone acetate

The effects of cyproterone acetate (CA), daily oral administration of 100 mg/m2, on the levels of urinary androgen excretion and velocity of skeletal maturation were studied in 8 girl patients with precocious puberty. Under therapy, testosterone excretion fell within a short time, and velocity of skeletal maturation normalized when the treatment was prolonged. Other beneficial effects such as stoppage of vaginal bleeding and no further growth of breast size and public hair, were also observed. Of 3 subjects, who were given CA for a period of 2--3 yrs, 2 showed further increments in testosterone excretion levels.

Plasma estrogen and androgen concentrations in children during adolescence

Using Sephadex LH-20 chromatography and a radioimmunological technique, the simultaneous measurement of estrone, estradiol, testosterone and dihydrotestosterone was performed in a single extract of peripheral plasma in children. In 44 boys and 43 girls, the mean plasma concentration of estrone rose steadily in both sexes, though more pronounced in the girls. For estradiol, this increment was noted only for the girls. For testosterone, the boys showed a spurt after pubertal stage 3, whereas the girls did not show any rise throughout the developmental phases. The girls, however, showed increment in dihydrotestosterone, concentration from pubertal stage 1 to 3, and plateaued thereafter. The boys showed marked increment in the concentration of this steroid throughout development, although less pronounced as that seen for testosterone. Plasma estrogens correlated better with the clinical evaluation of sexual maturation than with chronological ages in the girls. Similarly, the boys showed better relationship between the androgens and maturational stages than with chronological age. The girls also demonstrated a steep increment in the SDs for the estrogen values with sexual maturation (at stages 3 and 4, the SDs for estrone and estradiol were 0.26 and 0.80 respectively, at stage 5 they were 0.82 and 1.49 respectively) reflecting perhaps the onset of cyclic activity. When the estrogen values were related to the androgen values, the boys demonstrated a high association (r equals 0.78). This correlation was absent in the girls.

Effects of experimental bilateral cryptorchidism and castration on the plasma gonadotropins in male rats during sexual maturation

The effect of bilateral cryptorchidism and castration on serum LH and FSH was assessed in rats throughout their sexual maturation. After short time (4 days) castration marked elevations of FSH and increases of LH in plasma are recorded in all developmental stages. Bilateral cryptorchidism caused after 4 days in different age groups elevations of LH regardless of the sexual maturation. FSH was elevated in these cryptorchid animals only in more mature animals.

The effect of HCG on testicular androgen production in adult men with chronic renal failure

In sixteen male patients undergoing regular haemodialysis of peritoneal dialysis for chronic renal failure, the testosterone levels were studied before and after treatment with HCG. Testosterone values before (186 ng/100 ml) and after (456 ng/100 ml) HCG were significantly lower than those for normal healthy males. The mean plasma dihydrotestosterone (5alpha-DHT) value of 11.5 ng/100 ml for the treated patients was significantly lower than that of 64 ng/100 ml for the control patients. With HCG, increments in DHT were recorded in three patients, and definite increments in testosterone were observed in six patients. The percentage binding and combining affinity showed little change due to HCG stimulation. Achieving ejaculation was a serious problem for the patients in whom the lowest increases in testosterone and 5 alpha-DHT levels were observed after HCG stimulation. Low plasma testosterone values were also associated with a low mean area for Type-2 muscle fibres.

Plasma testosterone and dihydrotestosterone in male rats during sexual maturation and following orchidectomy and experimental bilateral cryptorchidism

Plasma concentration of testosterone and dihydrotestosterone (17beta-hydroxy-5alpha-androstan-3-one) were measured at frequent intervals (daily between day 20 and 40) in intact male rats from early pre-pubertal stage to full maturity. Effect of orchidectomy and experimental bilateral cryptorchidism on these two blood-born compounds at different stages of sexual maturation was also studied. A distinct spurt in testosterone level was noted on day 26, and in 3 days a leval of 2600pg/ml was reached, which was about 90% of the highest peak value (2940 pg/ml) seen at day 70. In the same animals dihydrotestosterone spurt was noted at the same time, but the peak value (163 pg/ml) was reached later (day 33). Within 4 days after orchidectomy plasma testosterone level showed no significant change in 20-day old animals, but dropped to 15% of the intact value in 40-day old ones, while remaining at a steady level of about 23% in older animals. Plasma dihydrotestosterone was undetectable after orchidectomy at each stage of sexual maturation. With bilateral cryptorchid animals plasma testosterone was higher than seen in the intact 20-day old control, but remained similar at other stages of sexual maturation. Plasma dihydrotesterone in the same animals was significantly less (p less 0.01) than those seen in the intact controls at all stages of sexual development except in 20-day old ones, where it was essentially similar.