Photoperiodicity and circannual levels of LH, FSH, and testosterone in normal and castrated male, white-tailed deer

To establish the relation between photoperiodicity and the levels of LH, FSH, and testosterone (T) in plasma, three intact and three castrated adult male white-tailed deer were sampled once a month for 2-3 years. The rang of average LH levels in controls varied between 0.8 and 2.0 ng/mL; the levels in castrates were considerably higher, 3.4 to 8.9 ng/mL. Average levels of FSH varied in controls between 25 and 112 ng/mL and in castrates between 141 and 240 ng/mL. A significant correlation between the seasonal time course of LH and FSH was found in castrated, but not in intact bucks. In castrates both gonadotropins exhibit two major elevations coinciding with spring and fall equinoxes in March and September. The seasonal time course of FSH in castrates correlates highly with seasonal levels of FSH in controls. However, the time course of the LH curve in controls is substantially different from the curve in castrates, presumably owing to feedback mechanisms. A possible role of testicular estradiol in this feedback is discussed. In controls, peak T levels are reached in December, i.e., 3 months after maximum levels of FSH and 5 months after peak levels of LH were detected. It appears that male deer undergo two periods of reproductive stimulation (one in the spring, the other in the fall). However, the organism responds with the full range of gonadal and behavioral mechanisms leading to the initiation of the rut only during the fall.     

Thyroxine levels and antler growth in white-tailed deer

1. Five normal male, 5 female, and 3 castrated fawns and 5 adult male white-tailed deer were housed in individual pens for one year to compare the relationships between thyroxine (T4) and other blood parameters and the antler cycle. 2. Biweekly serum samples were examined for T4 titers and levels of serum calcium (Ca), inorganic phosphorus (P), and alkaline phosphatase activity (AP). 3. Seasonal T4 changes were found in all deer groups, with elevated titers in the fall. Female fawns had overall lowered T4 levels. In male fawns and adult bucks, T4 seemed to play a synergistic role in antler initiation and growth. 4. Serum Ca levels remained constant throughout the year, but with lower levels in the female fawns. 5. Serum P levels were also constant seasonally, but with higher levels in the female fawns. There was no age effect on either Ca or P. 6. An age effect was evident on plasma alkaline phosphatase with lower activity in adult bucks. There was no sex effect on AP activity. 7. T4 might have an indirect association with the enzyme AP in Ca and P transport system in white-tailed deer.     

Effect of pinealectomy on seasonal changes in antler growth and concentrations of testosterone and prolactin in white-tailed deer

A 2-year study was conducted to determine under controlled conditions the role of the pineal gland in regulating the seasonal changes in antler growth and reproduction of male white-tailed deer. Blood samples were drawn from 6 pinealectomized (PX) and 18 control (C) deer at intervals of 2 weeks and analyzed for testosterone (T) and prolactin (Prl). Relative scrotal circumference and main beam antler length were recorded. Relative scrotal circumference was similar in PX and C groups, but the normal pattern was delayed 1 to 3 months in the PX deer relative to the C deer. The mean dates of beginning antler growth, velvet shedding, antler casting and pelage changes were significantly later in both years for PX deer than in C deer. Testosterone concentrations peaked 1 month later in the PX deer than in the C deer for both yearling and 2-year-old deer. Prl concentrations in C deer, but not in PX deer, were correlated highly with day length, and the PX deer were delayed relative to the C deer in showing the normal Prl pattern. Increasing levels of Prl in both groups coincided with beginning antler growth in both years. These results indicate that the pineal gland does not originate the seasonal cycles of male white-tailed deer but may synchronize cycles among individual deer, and regulate the circannual rhythm of Prl concentrations which may in turn influence other hormonal cycles.     

Circadian and circannual rhythms of LH, FSH, testosterone (T), prolactin, cortisol, T3 and T4 in plasma of mature, male white-tailed deer

Circadian and circannual rhythm of plasma LH, FSH, testosterone (T), prolactin, cortisol, triiodothyronine (T3) and thyroxine (T4) were investigated in two mature male white-tailed deer. No circadian rhythms were detected. Seasonal levels of LH and FSH were reached in September and October; troughs occur in May and June. Maximal T values were detected in November and December (the time of the rut); minimal levels occur between February and July. Prolactin peaked in May and June; minimal levels were detected between October and February. T3 exhibited two maxima; the first in the May-June period, the second in the September-October period. T4 showed no recognizable circannual rhythm. Cortisol levels were found to be much higher during cold months (December-April) than during the rest of the year. The least variable circadian levels were that of FSH and prolactin, with LH, T4, T3, cortisol and testosterone following in descending order. Cannulation stress might have some effect on the levels of testosterone, LH and cortisol. Correlation between LH and testosterone levels were detected mainly during sexually active periods.     

Seasonal levels of LH, FSH, testosterone and prolactin in adult male pudu (Pudu puda)

Seasonal levels of LH, FSH, testosterone (T) and prolactin (PRL) were determined in plasma of six captive adult male pudu (Pudu puda) kept in Concepcion, Chile. Average PRL levels exhibited one peak (28 ng/ml) in December (summer); minimal levels (3 to 6 ng/ml) were detected between April and July. FSH concentrations remained at peak levels (54–63 ng/ml) from December until March; minimal values (25–33 ng/ml) were detected from April until October. T levels exhibited two, almost equal peaks; the first peak (2.8 ng/ml) was detected in March (rut) and the second one (2.7 ng/ml) in October (spring). Both T peaks were preceded by an earlier elevation of LH in February and July (both around 1.3 ng/ml). During the fall, only the alpha male exhibited a sharp peak of T (8.4 ng/ml), whereas in the spring five out of six bucks demonstrated an increase of T levels. Two peaks of LH and T and the 4 months of elevated FSH may be related to a long period of spermatogenesis observed in this species.     

The effect of FSH on LH induced testosterone secretion in the immature hypophysectomized male rat

The effect of gonadotropin pretreatment of hypophysectomized male rats on LH stimulated serum testosterone concentrations was studied. A 5 day pretreatment period began 2 days after hypophysectomy at 21 or 24 days of age. On the day following the pretreatment period the animals received an intraperitoneal injection of saline or LH 60 min before blood collection. Animals pretreated with NIH-FSH-B1, or with doses of LH approximating the amount present in the NIH-FSH, had increased testosterone concentrations after LH stimulation compared to similarly stimulated saline pretreated animals. Pretreatment with more highly purified FSH Ex 199C at a lower dose than the minimum effective dose of NIH-FSH was also effective. There was no synergistic or additive effect when FSH Ex 199C and LH pretreatments were combined. FSH Ex 199C is more potent and contains appreciably less LH contamination than NIH-FSH-B1. The results obtained using FSH Ex 199C indicate that FSH, independent of LH contamination, can increase testes response to LH stimulation.     

Preliminary observations on the existing relationship between plasma levels of prolactin and hypophyseal reserves of FSH and LH in the male

PRL plasma levels and FSH and LH pituitary reserve were tested in ten apparently healthy male subjects. A good correlation was found between PRL on one hand and FSH plasma levels (p less than 0,05), LH plasma levels (p less than 0,01) and FSH pituitary reserve (p less than 0,01) on the other hand. This seems to support the current hypothesis that prolactin may cause a progressive clinically latent impairment in the spermatogenetic function of the testis. Further evidence is needed.     

Effect of mouse epidermal growth factor on plasma concentrations of LH, FSH and testosterone in rams

Two experiments were conducted to examine the effects of mouse epidermal growth factor (EGF) on the concentrations of testosterone, LH and FSH in jugular blood plasma and on the pituitary responsiveness to LHRH. In 20 rams treated with subcutaneous doses of EGF at rates of 85, 98 or 113 micrograms/kg fleece-free body weight, mean plasma LH and testosterone concentrations were significantly reduced (P less than 0.05) at 6 h after treatment but not at 24 h. EGF treatment at 130 micrograms/kg fleece-free body weight suppressed the plasma content of these hormones for up to 48 h. Mean plasma FSH concentrations decreased significantly (P less than 0.05) for up to 48 h after EGF treatment, the effect being most pronounced in rams with mean pretreatment FSH values greater than or equal to 0.5 ng/ml. Intravenous injections of 1.0 micrograms LHRH given to each of 5 rams before and at 6 h, 24 h and 72 h after EGF treatment produced LH and testosterone release patterns which paralleled those obtained in 5 control rams similarly treated with LHRH. These results suggest that, in rams, depilatory doses of mouse EGF temporarily impair gonadotrophin and androgen secretion by inhibiting LHRH release from the hypothalamus. Such treatment appears to have no effect on the responsiveness of the pituitary to LHRH.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection

Adult male rhesus were treated with PGE₂, PGF_2α or the 13,14-dihydro-15-keto metabolite of PGE₂ in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF_2α was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE₂ was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE₂ or PGF_2α can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.     

Testosterone and estradiol concentrations in serum, velvet skin, and growing antler bone of male white-tailed deer

The growth and mineralization of antlers correlate with the seasonal variation of serum androgens. Whereas seasonal levels of testosterone (T) in plasma are well established, steroid concentrations have not yet been determined in the tissues of growing antlers. Therefore, RIA was used to determine T and 17beta estradiol (E2) in serum, and three areas (tip, middle, and base) of the antler bone and the antler skin, called velvet. Blood and antler tissues of white-tailed deer (Odocoileus virginianus) were collected from May to August. The difference between levels of T and E2 among the sites was calculated using the square root transformation followed by a mixed model analysis with individual deer and an interaction of individual and year (individual(*)year) as a random factor. Concentrations of T in serum (799+/-82 pg/ml) were higher than T values in the velvet (589+/-58 pg/ml, P<0.01) and in the antler bone (538+/-58 pg/ml, P<0.001). Estradiol concentrations differed among antler tissues and serum (P<0.001) and between years (P<0.01). Estradiol concentrations in serum (25+/-25 pg/ml) were consistently lower than those in antler bone (208+/-11 pg/ml, P<0.001) and velvet (150+/-12 pg/ml, P<0.001). The E2:T ratio in serum was 1:10-60. The same ratio for the antler bone was only 1:2-3 and for the velvet 1:3.5. It is concluded that higher T and lower E2 concentrations found in plasma, as compared to antler bone or antler velvet, may indicate a partial metabolism of systemic androgens into estrogens xin the tissues of growing antlers.     

Antler cycle and endocrine parameters in male axis deer (Axis axis): seasonal levels of LH, FSH, testosterone, and prolactin and results of GnRH and ACTH challenge tests.

1. Antler cycles of six adult male axis deer of southern Texas were relatively well synchronized within the herd. The old antlers were cast from December to March and regenerated antlers polished between March and June. The rutting season occurred in June and July. 2. LH and FSH exhibited little seasonal variation (LH 0.7-1.3 ng/ml; FSH 32-65 ng/ml). Prolactin levels were lowest in December (20 ng/ml) and highest in June (115 ng/ml). Testosterone concentrations exhibited a distinct seasonal pattern: minimum in December (0.1 ng/ml) and maximum in May (1.75 ng/ml). 3. After GnRH challenge (100 micrograms given i.m. in November), maximal LH levels (reached 40-60 min after injection), varied from 7.7 to 11.2 ng/ml, and T levels varied from 1.3 to 1.6 ng/ml. 4. Twenty I.U. of ACTH (given in March), elevated cortisol levels from 4-8 micrograms/dl (pretreatment) to 16-21 micrograms/dl (140 min post-administration).     

On the correlation between FSH, LH and prolactin serum levels.

In 188 males FSH, LH, and prolactin serum levels determined from a single blood sample were found to be closely correlated. No correlation appeared to testosterone levels. The same correlation is observed, if serum levels of FSH, LH, and prolactin are measured after stimulation with LH-RH and TRH. In order to explain the close correlation, in five young men hormone levels were measured at 2-min-intervals over a period of 2 hours. Peaks of prolactin often correspond to those of FSH and LH, and a statistical correlation was found in two cases between FSH and prolactin. Results suggest a common releasing mechanism, which is superposed to the main mediating mechanism.     

Alterations in plasma concentrations of testosterone, LH, and prolactin associated with mating in the male rat.

The hormonal response of the male rat to sexual activity was investigated in two studies. In the first, no evidence of a chronic elevation in plasma levels of testosterone (T), LH, or prolactin (PRL) was observed in sexually experienced rats compared to naive controls. Both groups showed an acute increase in plasma levels of all three hormones following mating, but the increases shown by the experienced group were more pronounced. In the second study, plasma levels of T, LH and PRL rose in sexually experienced male rats following exposure to a mating arena whether it contained an estrous female, an anestrous female, or no other animal. However, the increases were considerably larger in the group exposed to estrous females. It is suggested that plasma hormones rise in anticipation of mating, although not to the same extent as following mating, and that the anticipatory rise may function to initiate or facilitate mating behavior.     

The effect of yohimbine on plasma levels of T3, T4 and cortisol in xylazine-immobilized white-tailed deer

1. The effect of yohimbine (Y) on blood levels of thyroxine (T4), triiodothyronine (T3), and cortisol was investigated in 5 mature male white-tailed deer immobilized with xylazine hydrochloride (X). 2. T4 levels were erratic in X-treated deer, but stabilized in the X- and Y-treated deer. 3. T3 remained unchanged in both groups. 4. Cortisol levels have increased in X-treated deer, but declined in X- and Y-treated deer. 5. Yohimbine is a potent and safe antidote of X not affecting T3 and T4. Caution should be used in using R or Y in cortisol studies.     

Serum FSH, LH and testosterone in the male rhesus following prostaglandin injection.

Adult male rhesus were treated with PGE2, PGF2 alpha or the 13,14-dihydro-15-keto metabolite of PGE2 in a randomized crossover design. Serum concentrations of FSH, LH and testosterone were determined and compared to the respective values in the same uninjected animals. No significant changes were noted in controls or following the metabolite injection. FSH increased gradually for 4 hours after metabolite treatment. In contrast, injection of PGF2 alpha was followed by an abrupt (within 15 minutes) increase in LH and testosterone. FSH increased gradually in 2 of 3 treated animals. Injection of PGE2 was followed by a similar abrupt increase in LH concentration. This was not always associated with a significant increase in testosterone or FSH. These results demonstrate that injections of PGE2 or PGF2 alpha can change serum gonadotropin and testosterone concentrations in male rhesus monkeys, and that the effects of these two prostaglandins are qualitatively different.