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Introduction: The perspectives of rural communities, specifically people with lived experience of suicidality and suicide loss in rural places, are often neglected in suicide research. It is critical that rural and remote health researchers acquire a deeper understanding of suicidality in rural Canadian communities for generation of relevant knowledge to better inform the development of suicide prevention, intervention and postvention solutions. This article presents research findings of how rural residents understand their community values, what information gaps they identify in relation to current suicide research, and how research can be mobilized to reach rural communities., Method: Researchers conducted six virtual focus groups with 47 participants from the Canadian provinces of British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, and Newfoundland and Labrador between March and May 2021. All focus groups were transcribed verbatim and analyzed using thematic analysis., Results: Focus group findings revealed the need for research that recognizes the significance of rural culture, the sense of community experienced and the ways in which they shape rural suicide experiences with associated impacts of suicide. Participatory, community-based action research methods are required to examine the interplay between rural residence, community, and suicide. In addition, the voices of rural people with lived experience of suicide are absent in the research literature. The need exists for qualitative research conducted for the purpose of investigating the lived experience of rural suicidality., Conclusion: Research participants asked that a lived experience agenda be prioritized to include the voices and stories of rural people, with consideration of rural culture, an aspect of rural suicidality currently not evident in Canadian research literature.

Horseracing is among the most popular and increasingly lucrative industry sports in the nation. The average jockey must control a thoroughbred horse 10 times their weight that may act unpredictably whether at rest or full gallop resulting in falls, kicks, or even biting injuries. Despite the risks, jockeys do not have access to the same quality of medical care that is standard in similarly profitable sports organizations. Beyond the mental and physical demands of training and performance endured by any professional athlete, jockeys are confronted with health challenges unique to their sport. In this review of the literature, we aim to educate sports medicine physicians regarding the underlying causes of injuries, describe injury management, and make recommendations for appropriate preventive strategies. Overall, there is a void of literature, and so our authors offer expert opinion and encourage others to get involved in making this a safer sport.

Objectives: To measure the incidence of homelessness among youths discharged from an inpatient facility as well as to identify factors that place these youths at risk for homelessness., Method: Reports of homelessness during 5 years of follow-up interviews with 83 adolescents consecutively discharged from an inpatient facility were used in conjunction with chart reviews., Results: One third of youths experienced at least one homeless episode after discharge. Youths who had a history of substance use, physical abuse, running away, or being in state custody were more likely to become homeless than those without such factors. Having a thought disorder, however, was inversely related to becoming homeless after hospital discharge., Conclusions: Youths discharged from a residential treatment facility are at high risk for becoming homeless. Interventions to prevent homelessness among adolescent inpatients should be targeted to those with a history of substance abuse, physical abuse, running away, and being in state custody.

Objective: This study examined the differential effects of various forms of abuse, as well as their combined effects. The study also sought to separate the factors uniquely associated with abuse from those associated with the more general problems present in an abusive family environment., Methodology: Data were collected from 329 homeless adolescents. Preliminary analyses indicated some degree of matching for family background variables. Any differences in demographic or family characteristics were controlled for statistically., Results: Chi-square analyses revealed significant differences across groups for rates of assault, rape, depression/dysthymia, and attempted suicide. Multivariate analyses (MANOVAs) indicated significant differences in severity of internalizing problems and cognitive problems. Without exception, the group with histories of both physical and sexual abuse exhibited the most severe symptomatology and was at greatest risk for revictimization. Multiple regression analyses suggested that abuse histories were predictive of internalizing problems while family characteristics were more predictive of externalizing problems., Conclusions: The findings indicate that both abuse type and family characteristics contribute to the development of symptomatology. Future prospective and longitudinal studies are needed to clarify the sequelae of abuse, as well as the possible cause and effect relations between abuse, family characteristics, and psychological outcome.

These studies were an examination of the changes in function of the pineal gland and its secretory product, melatonin, during sexual maturation induced by stimulatory photoperiod in ferrets. Plasma melatonin patterns were determined for 48-h intervals in ferrets undergoing photoperiod-stimulated sexual maturation. Sampling regimens were conducted when ferrets were 10, 15, 16, and 23 wk of age. Clear daily rhythms in melatonin concentrations were apparent in ferrets as young as 10 wk of age. Melatonin secretion increased with the onset of darkness each day and fell with lights-on the next morning. When the photoperiod was changed from a short day (8L:16D) to a long day (16L:8D) at 15 wk of age, the melatonin rise did not contract immediately to the shorter dark phase for at least the first two nights. By 1 wk after imposition of the new, long-day photoperiod, however, the pattern of melatonin concentrations in plasma was synchronized to the new photoperiod. These studies show that ferrets can detect photoperiod at a much younger age than that at which they can respond to long days with accelerated maturation and further, that while the pineal gland mediates the photoperiod-induced maturation of ferrets, other factors are involved in the 5-6-wk interval between the onset of long days and the maturational response of the hypothalamo-hypophyseal-gonadal axis in this species.

The physical therapy and orthopedic management of patients with myelodysplasia from infancy to adulthood are reviewed. The overall goal for the child with myelodysplasia is functional independence. Physical therapy and orthopedic intervention enable the individual to achieve this goal. Associated problems, however, such as Arnold-Chiari malformation, hydrocephalus, and tethered spinal cord, influence functional expectations. Physical therapy management begins in the neonatal period and continues through adolescence. Treatment is modified at the various stages of development. Knowledge of current orthotic and adaptive equipment is necessary to achieve optimal locomotor function. Orthopedic management decisions are based on musculoskeletal and neurologic assessments, to which the physical therapist provides a significant contribution. Controversies exist over the orthopedic management of dislocated hips, scoliosis, and kyphosis.

This report provides evidence that an increment in serum gonadotropin levels occurs at puberty in the sheep and that this reflects the critical hormonal event culminating in first ovulation in this species. Blood samples were collected from 6 female lambs at 4-h intervals for a period of approximately 2 mo around the expected time of puberty (32 wk of age) until behavioral estrus was observed and ovulation was verified by assay of serum progesterone. Patterns of circulating LH, FSH, progesterone, and estradiol concentrations were characterized during the peripubertal period for each lamb. A rise in serum levels of both LH and FSH began approximately 7-10 days before the first preovulatory surge of gonadotropins. Although the increase in gonadotropin levels occurred gradually over several days, serum estradiol levels rose only during the final 40-60 h prior to the preovulatory surge of gonadotropin. Serum progesterone profiles revealed, however, that normal (14-16-day) luteal phases were induced in only 2 of 6 females as a result of the first surge. In four lambs, a short luteal phase of 2.5 days' duration occurred, which was followed by another estradiol rise and a preovulatory surge that then resulted in a full luteal phase of 14 days' duration. These data demonstrate clearly that the precipitating event at puberty in the female sheep is an increase in circulating gonadotropin levels and that the estradiol secreted from the newly stimulated follicle provides the signal for the first preovulatory surge.

This study determined whether a rise in tonic secretion of LH occurred before long day-induced precocious puberty of the female ferret. Twenty immature females were assigned to 1 of 2 photoperiods at 15 weeks of age. Ten ferrets were placed in a long day, stimulatory photoperiod (16 h of light, 8 h of darkness) to induce sexual maturation, and 10 remained in the nonstimulatory photoperiod (8 h of light, 16 h of darkness) for the duration of the study. Intensive blood sampling regimens (every 10 min for 8 h) were conducted at selected times after the onset of long days to permit definition of detailed secretory patterns of plasma LH. Females in each photoperiod were sampled from chronic jugular venous catheters approximately twice weekly until puberty was evident in females housed in long days. The end point for determination of the pubertal onset of adult ovarian function was the appearance of estrogen-sensitive vulvar edema. Results show a marked increase in frequency of episodes of LH secretion per 8-h interval in females undergoing sexual maturation. No such change in frequency occurred in unstimulated females housed continuously in short days, nor did the short day females exhibit vulvar edema. Further, the increment in LH secretion occurred before either vulvar edema or a significant increase in plasma estradiol levels was observed. Therefore, the rise in LH secretion that occurs after several weeks of exposure to a long day photoperiod may well be an important drive to maturational changes in ovarian function.

Although ferrets are long-day breeders, females reared exclusively in nonstimulatory short days will undergo spontaneous sexual maturation by 30-50 wk of age. In the following report, this spontaneous sexual maturation of ferrets was studied to determine mechanisms regulating sexual maturation in nonstimulatory photoperiods. Study of ovariectomized females treated with low, constant levels of estradiol suggest that a marked decrease in the efficacy of estradiol to inhibit luteinizing hormone secretion occurs shortly before sexual maturity becomes evident in intact controls (both groups housed in short days). During this long juvenile period, a marked increase in body weight occurred, but ovarian responsiveness to exogenous gonadotropin did not change. Older, larger females did respond more rapidly to stimulatory photoperiod than did younger females. These studies suggest that the mechanisms of spontaneous puberty in ferrets are likely the same as those regulating photoperiod-stimulated puberty in this species.

The purpose of this study was to examine the role of circulating 17 beta-estradiol in the regulation of pituitary gonadotropin secretion and, hence, ovarian maturation in immature female ferrets. The hypersensitive negative feedback relationship between the ovaries and the hypothalamo-pituitary axis in developing ferrets was disrupted by infusion of a specific antiserum to 17 beta-estradiol. The effect of this treatment on gonadotropin secretion and ovarian morphology was contrasted with that observed in intact age-matched control females treated with a nonimmune gamma-globulin preparation. Infusion of the antibody into intact immature ferrets caused, within 48 h, an increase in pulsatile secretion of LH to 0.67 +/- 0.06 pulses/h over that observed in intact females treated with control gamma-globulin (0.13 +/- 0.06 pulses/h). This increase in pulse frequency was similar to that observed 48 h after ovariectomy of young animals (0.70 +/- 0.12 pulses/h). Furthermore, this level of gonadotropin secretion in antibody-treated animals resulted in stimulation of antral follicle growth in ovaries of these females. Ferrets treated with specific antiserum to 17 beta-estradiol showed a significant increase in numbers of ovarian follicles greater than 0.3 mm in diameter compared to those in ovaries of females treated with control gamma-globulin. These data strongly suggest that the limiting event at puberty in the ferret is the rise in gonadotropin secretion which is allowed by the pubertal decrease in efficacy of 17 beta-estradiol to inhibit gonadotropin secretion.

Sexual maturation of immature ferrets in response to a stimulatory photoperiod generally occurs within 6-7 weeks after imposition of long days at 16 weeks of age. In this study, females were examined for evidence of ovarian maturation after 22 days of exposure to the stimulatory photoperiod, before any sign of sexual maturation. The photoperiod-stimulated and control females were the same age (19 weeks), had similar body weights, and showed no evidence of vulvar oedema. Comparison of oestradiol secretory response to hCG stimulation and of follicular development in the ovary revealed marked ovarian stimulation in females kept in long days compared to control females kept in short days. A prolonged period of ovarian stimulation therefore occurs during exposure to long days before there is external evidence of sexual maturation in ferrets.

Seasonal variations in the behavioural and feedback actions of oestradiol in the ewe were examined by determining the ability of various physiological oestradiol concentrations to elicit oestrous behaviour, induce an LH surge, and suppress tonic LH secretion at four times of the year. These tests were performed in acutely ovariectomized animals pretreated with oestradiol and progesterone to minimize seasonal differences in their endocrine status. Although smaller amplitude LH surges were observed in anoestrus, the dose-response curves for the induction of LH surges were virtually identical at all times of the year. Oestradiol was slightly less effective in eliciting oestrous behaviour in anoestrus and during the transition to the breeding season than at other times. This seasonal variation was, however, observed only with relatively low oestradiol concentrations; serum oestradiol levels of 3 pg/ml or greater induced oestrus in almost all ewes regardless of season. In contrast, there was a marked seasonal change in the negative feedback action of oestradiol. In anoestrus, basal oestradiol levels of 1-3 pg/ml suppressed LH to low levels (0.3 ng/ml), whereas in the breeding season, even peak oestradiol concentrations of 10 pg/ml were not able to produce this degree of inhibition. These results thus support the hypothesis that the annual breeding cycle of the ewe is governed primarily by shifts in the extent to which oestradiol can suppress tonic LH secretion.

Endocrine changes mediating male-induced estrus were examined in intact female mice which were rendered pseudopregnant by housing in groups. Adult female mice were placed in group cages on the day of estrus, and on day 5 of the ensuing pseudopregnancy, a mature male mouse was placed in the group cage. Animals were killed and serum levels of LH, FSH, PRL, estradiol, and progesterone were assayed over the 72 h after introduction of the male. During the first 24 h of male exposure, progesterone plummeted to basal levels. These events were followed by a gradual rise in serum estradiol, an increase in uterine weight, and an LH surge at 62 h which was followed by ovulation. PRL levels tended to be lower in treated females, but this was not significant. It is postulated that the initial exercise of the male is to destroy the corpus luteum of pseudopregnancy,presumably by suppressing luteal support. The question is raised of whether the male is also necessary to induce the subsequent LH surge or if suppression of the corpus luteum is sufficient for estrus to result.

It is proposed that the first follicular phase in the lamb is initiated when responsiveness to oestradiol inhibition of LH secretion decreases sufficiently to permit the expression of an inherent hourly LH pulse rhythm. The hourly LH pulse rhythm is believed to drive oestradiol production to levels that induce the first LH surge. This hypothesis is based upon several considerations. First, pulsatile LH secretion invariably occurs at low frequencies in immature lambs whereas hourly pulses are manifest in postpubertal lambs and mature ewes during the follicular phase of the oestrous cycle. Second, intravenous administration of LH at hourly intervals to immature lambs results in an increase in follicular size, induction of an LH surge, ovulation and corpus luteum formation. Third, hourly LH pulses will occur in the immature female if the ovaries are removed; the hourly frequency in the immature ovariectomized lamb can be reduced by exogenous oestradiol. Fourth, in the chronically oestradiol-treated ovariectomized lamb, responsiveness to oestradiol inhibition of LH secretion becomes markedly decreased during the pubertal period, and the hourly LH pulse rhythm is expressed. It is further proposed that a minimum body weight and short daylengths are necessary for the reduction in oestradiol negative feedback. With regard to photoperiod, the delay in onset of cyclicity in lambs born in the wrong season (autumn) may be due to retarded maturation or post-maturational seasonal anoestrus.

The purpose of this study was to examine the pituitary-ovarian relationship of both estrous and anestrous female ferrets. The endocrine status of the animals was induced by manipulating photoperiod: females in estrus were housed in long days (16L:8D); females in anestrus were housed in short days (8L:16D). For studies of intact animals in both photoperiods, plasma luteinizing hormone (LH) levels were quantified in blood samples collected from adult ferrets at 5-min intervals over a 24-h period. Similar groups of females (estrous and anestrous) were ovariectomized (while remaining in their assigned photoperiods) and blood samples were collected at 5-min intervals for 4-h periods on Days 1, 2, 4, 10, 17, and 35 after ovariectomy. Intact, estrous females exhibited continuously low or undetectable levels of LH with no evidence of episodic secretion. Ovariectomy of these estrous animals resulted in rapid onset (within 24 h) of episodic LH secretion, with pulses occurring in excess of 1 pulse/h. No substantial further change in frequency or amplitude of pulses occurred in these females from 1 to 35 days postovariectomy. In contrast, intact anestrous ferrets exhibited clear episodic LH secretion at a frequency of about 0.4 pulses/h. Removal of ovaries from these females caused no change in LH secretion for 24-48 h, after which LH pulses gradually increased in frequency. By 18 days after ovariectomy, LH patterns were indistinguishable among ovariectomized females in long and short days. These studies suggest a major site of ovarian negative feedback on LH secretion during anestrus is the hypothalamus, whereas the site of the ovarian feedback in estrous females is not yet evident.

The role of PRL in sexual maturation of female ferrets was examined in these studies. Longitudinal profiles of PRL secretion were obtained by thrice weekly blood sampling of intact female ferrets undergoing photoperiod-stimulated development as well as age-matched control females which remained in nonstimulatory short days. Two additional groups of intact females, one in each photocycle, were treated with the dopamine agonist drug bromocriptine throughout the study. The relationship between developmental changes in PRL secretion and the critical pubertal decrease in the efficacy of estradiol (E2) inhibitory feedback on LH secretion was studied by using additional groups of females which were ovariectomized and treated with E2 implants (OVX + E2). These latter females were housed in either long or short day photoperiods; some were treated with bromocriptine, the remainder were treated with the vehicle only. Results of this study revealed that PRL secretion in ferrets does not change acutely with an abrupt increase in day length. After 4 weeks of exposure to long days, however, a marked increase in PRL secretion occurred. This increased secretion of PRL was contemporaneous with the onset of pubertal ovarian activity in intact females and with the escape of LH from the negative feedback of E2 in OVX + E2-treated females. The further observation that pharmacological blockade of the long day-induced rise in PRL secretion also prevented the pubertal onset of ovarian activity suggested that PRL may play a critical role in the induction of puberty in this species. The mechanism by which bromocriptine prevented puberty induction was illustrated in the OVX + E2-treated ferrets in stimulatory photoperiod. The drug treatment prevented the pubertal decrease in the efficacy of E2 negative feedback on LH. These studies suggest an important interaction between the dopamine-PRL system and the GnRH-LH system in the regulation of sexual maturation of female ferrets.

This investigation examined the effects of repeated injections of LH on ovarian function in the immature sheep approximately 12 weeks before the time of the first expected spontaneous ovulation. The frequency of endogenous LH pulses during the pretreatment period was approximately one pulse each 3 h. The first experiment determined that rapid injection (iv) of 15.5 micrograms LH replicated the amplitude of endogenous pulses. Hourly injection of this dose for 48 h to simulate the rapid LH pulse frequency of the follicular phase of the postpubertal female induced a LH surge and ovulation in two of three lambs. By contrast, administration of 33% of the dose over the 48-h period did not [5.2 micrograms/h (three lambs) or 15.5 micrograms each 3 h (three lambs)]. The second experiment (seven lambs) determined the time course of the preovulatory estradiol rise produced in response to hourly LH pulses (15.5 micrograms/injection), as well as the length of the luteal phase after the induced LH surge. Four lambs produced a sustained estradiol rise, a LH surge, and ovulation. The luteal phase was normal (13 days) in one and short in three lambs (6-11 days). In the remaining three prepubertal females that did not ovulate in response to 48-h injections of LH, the estradiol rise was not sustained. Circulating estradiol in five untreated control lambs exhibited only transient increases during the course of the study. The results indicate that hourly administration of physiological quantities of LH over a relatively brief period (48 h) can produce a follicular phase culminating in first ovulation in the immature lamb. In the context of the mechanism proposed for puberty in the female sheep, the findings are consonant with the hypothesis that the hypothalamus, through its modulation of LH pulse frequency, governs the initiation of ovulation.

Patterns of circulating LH were examined in ovariectomized lambs and adults bearing Silastic capsules containing oestradiol-17 beta and in untreated ovariectomized lambs. A decrease in serum LH in oestradiol-treated lambs occurred coincidentally with the cessation of ovulations in intact lambs and in the absence of any decrease in circulating LH in untreated ovariectomized lambs. On average, these phenomena occurred 3 weeks before the seasonal reduction in serum LH levels and onset of anoestrus in oestradiol-treated ovariectomized and intact adults, respectively. The results suggest that (1) an early seasonal increase in responsiveness to oestradiol negative feedback on tonic LH secretion is responsible for the premature cessation of ovulations in the lamb, accounting, in part, for the short breeding season during the first year of life and, in some lambs, the failure to initiate cyclicity until the second year after birth; and (2) onset of anoestrus in lambs, in contrast to puberty, is not associated with steroid-independent changes in LH secretion.

Intact female lambs were chronically treated with low levels of oestradiol by Silastic implant from 20 weeks of age. Reproductive cycles were initiated in only 33% of these lambs (3 of 9) compared to 80% of untreated females (11 of 14) by 45 weeks when the study was terminated. Moreover, in the 3 oestradiol-treated lambs which began cycles, the age at first oestrus was delayed 3 weeks (37 +/- 1 weeks of age vs 34 +/- 1 weeks of age for untreated controls). Retardation of the pubertal process was not due to absence of the pubertal rise in circulating LH. At about 32 weeks of age, chronic oestradiol treatment was no longer able to suppress tonic LH secretion and serum LH increased in intact, oestradiol-treated lambs. These results indicate that a maturational decrease in responsiveness to oestradiol inhibition of tonic LH secretion can be demonstrated in the intact female, as in the ovariectomized female. However, chronic oestradiol suppression of prepubertal LH secretion also delays onset of reproductive cycles. This finding raises the possibility that low tonic LH secretion, presumably in the form of slow pulses, is necessary for development or maintenance of ovarian function before puberty. In the absence of LH during the last part of sexual maturation, the ability of the ovary to respond to the high frequency LH pulses during the pubertal gonadotrophin rise may be delayed.

It has been proposed that a seasonal increase in oestradiol negative feedback elicits anoestrus by preventing a key step in the preovulatory sequence of endocrine events, namely a sustained increase in tonic LH secretion. In the present study we compared the patterns of serum LH, FSH, oestradiol and progesterone after regression of the last corpus luteum of the breeding season, with their respective patterns during an ovulatory cycle in the late breeding season (samples obtained every 4 h from eight ewes). After regression of the last corpus luteum of the breeding season, serum LH and oestradiol showed distinct deviations from their respective late breeding season patterns. The rise in tonic LH secretion was curtailed. Further, there were no marked increases in oestradiol, despite a distinct, although brief, tonic LH rise; thus there were no gonadotrophin surges. If the hypothesis that the transition into anoestrus is caused solely by insufficient tonic LH secretion were correct, the brief increase in LH should have induced a transient rise in oestradiol. Since this was not the case, these results suggest that a decreased ovarian response to LH may also contribute to the termination of oestrous cyclicity at the transition to anoestrus.

In an attempt to develop an animal model wherein the pubertal process could be initiated or accelerated by a readily controlled, noninvasive, external signal, this study examined sexual development of the female ferret, a photoperiodic, reflex ovulator. These animals exhibit signs of precocious sexual maturation within 6 wk of exposure to a stimulatory, long-day photoperiod at 15 wk of age. In the first study, females matured under a long-day stimulus were allowed to mate with a fertile male ferret. All six females ovulated after mating, and three of six became pregnant and successfully delivered and reared litters, demonstrating that vulvar edema induced by long days reflected the onset of true precocious sexual maturation. The second study attempted to determine the endocrine basis of this photoperiod-induced puberty. Immature ferrets were either left intact or were ovariectomized at 13 wk of age. These females either remained untreated or immediately received an estradiol implant. Controls in each group remained in short days, and others were transferred to stimulatory long days at 16 wk of age. Results indicated that immature ferrets exhibited a rise in plasma luteinizing hormone (LH) upon ovariectomy, and that the extradiol implant was an effective negative feedback signal for the duration of the study in animals in short days. In contrast, females in long days exhibited an "escape" from LH inhibition by the steroid implant at the same age at which the intact females in long days were beginning to mature. These data suggest the young ferret exhibits a high sensitivity to estradiol negative feedback which is decreased in response to a stimulatory photoperiod, and which decrease is coincident with sexual maturation in intact animals under the same conditions.

The ontogeny of pulsatile LH and testosterone (T) secretion was studied in the developing male sheep. Three variables of LH secretion (frequency of LH pulses, magnitude of LH pulses, and the levels between pulses) were determined during a 6-h period at each of 1, 2, 3, 5, 7, 8, 12, and 16 weeks of age in six male lambs. Pulsatile LH secretion was evident by 1-2 weeks of age in rapidly growing lambs and by 3-7 weeks of age in slowly growing lambs. Although mean height of LH discharges increased 2-fold after the onset of pulsatile release, levels between discharges remained constant throughout the entire study. The most striking change, however, occurred in the frequency of LH discharges. The frequency increased 20-fold between weeks 1 and 8 and then decreased 3-fold between weeks 8 and 16. In each lamb, a brief (less than 3 h), but marked rise (greater than 2 ng/ml) in levels of circulating T occurred after the first observed pulse of LH. Thereafter, as the lambs became older, increased concentrations of serum T were observed only during periods of pulsatile LH secretion, the highest mean level of T occurring about 1 h after each LH peak. Administration of human chorionic gonadotropin (hCG) iv to 2-day-old males resulted in a marked increase in circulating T. A greater increment in concentrations of serum T occurred after the same absolute dose (50 IU) of hCG at 8 weeks of age than at 2 days of age. These results indicate that in the male lamb 1) pulsatile secretion of LH is initiated shortly after birth and changes in mean levels of LH are primarily a reflection of changes in frequency of LH discharges; 2) before the onset of pulsatile LH secretion, the testes are capable of responding to an exogenous LH-like gonadotropin with increased secretion of T; 3) after the onset of pulsatile LH secretion, a rise in circulating T follows each pulse of LH; and 4) an increase in capacity of the testes to secret T occurs during the first 8 weeks of postnatal life. It is concluded that the pattern of LH secretion, coupled with the capacity of the testes to secrete T, determines the pattern and magnitude of T secretion in the developing male sheep.