Effects of low levels of food intake before and/or after mating on gonadotrophin and progesterone profiles in Greyface ewes

1989 ◽  
Vol 49 (2) ◽  
pp. 267-273 ◽  
Author(s):  
S. M. Rhind ◽  
S. McMillen ◽  
G. Z. Wetherill ◽  
W. A. C. McKelvey ◽  
R. G. Gunn
Keyword(s):  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Metabolizable Energy ◽  
Energy Requirements ◽  
Plasma Samples ◽  
Nutritional Treatment ◽  
The Mean ◽  
Per Se ◽  
Low Levels

ABSTRACTGonadotrophin profiles during the follicular phase of the cycle prior to a synchronized mating and LH and progesterone profiles at days 2, 6 and 10 post mating were investigated in three groups of 16 ewes. of one group were given 0·5 × estimated metabolizable energy requirements for maintenance (MEM) from 14 days before mating until slaughter 11 days after mating (LL). Ewes of a second group were given 1·5 × MEM during the 14 days prior to mating and then 0·5 × MEM thereafter (HL) and the remaining ewes (HH) were given 1·5 × maintenance throughout the experiment. During the day before mating, plasma samples were collected at 10-min intervals for 8 h and assayed for LH and FSH. Samples were collected at 15-min intervals for 8 h on days 2, 6 and 10 after mating. Each ewe was then injected intravenously with 10 μg LH and samples were collected for a further 3 h. All of these samples were assayed for LH and progesterone. Nutritional treatment did not affect mean follicular phase concentrations of FSH or LH or mean LH pulse amplitude but the mean LH pulse frequency (pulses per h) of LL ewes was lower than that of HH + HL ewes (0·37 v. 0·48; P < 0·05). After mating, mean LH concentrations were unaffected by sampling date or nutritional treatment but the mean LH pulse frequency was lower in HL + LL than HH ewes at day 2 (0·25 v. 0·40; P < 0·01) and day 10 (0·28 v. 0·38; P < 0·05). Mean progesterone concentrations (ng/1) were higher in HL + LL than HH ewes at day 10 (6·77 v. 4·80; P < 0·05) but pulse frequency was not significantly affected. Injection of 10 μg LH on days 2, 6 and 10 after mating was followed by a significant increase in progesterone concentrations. The progesterone response was greater (P < 0·05) in LL + HL ewes than in HH ewes. It is concluded that increased rates of embryo mortality often associated with undernutrition are unlikely to be related to lower circulating progesterone levels per se but may be attributable to reductions in mean LH pulse frequency and consequent changes in progesterone profiles.

Effects of light and food on plasma leptin concentrations in ewes

2000 ◽  
Vol 71 (2) ◽  
pp. 235-242 ◽  
Author(s):  
T. Tokuda ◽  
T. Matsui ◽  
H. Yano
Keyword(s):  
Diurnal Rhythm ◽  
Energy Requirement ◽  
Pulse Length ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Pulse Plasma ◽  
Dark Cycle ◽  
Blood Samples ◽  
The Mean ◽  
Plasma Leptin

AbstractPlasma leptin concentration shows pulsatility and diurnal rhythm in humans. However, there are few reports concerning the 24-h profile of circulating leptin levels in ruminants. Five crossbred ewes were housed in metabolism cages under a 1-h light-dark cycle. The ewes were offered alfalfa hay daily to meet their energy requirement. Blood samples were collected at 15-min intervals for 24 h. Plasma leptin concentrations were determined using a radioimmunoassay and the profile of plasma leptin levels was analysed by the PULSAR algorithmic program for detecting pulse. Plasma leptin concentration changed in a pulsatile fashion. The mean leptin concentration was 2·93 ng/ml. The mean pulse frequency was 4·8 pulses per day and the mean pulse amplitude was 0·67 ng/ml with an average pulse length of 1:13 h. Plasma leptin level was not affected by feeding or lighting cycle. These results indicate that plasma leptin level in sheep shows pulsatility but diurnal rhythm is not exhibited.

Effect of restricted food intake, before and/or after mating, on the reproductive performance of Greyface ewes

1989 ◽  
Vol 48 (1) ◽  
pp. 149-155 ◽  
Author(s):  
S. M. Rhind ◽  
W. A. C. McKelvey ◽  
S. McMillen ◽  
R. G. Gunn ◽  
D. A. Eiston
Keyword(s):  
Food Intake ◽  
Reproductive Performance ◽  
Live Weight ◽  
Experimental Period ◽  
Metabolizable Energy ◽  
Ovulation Rate ◽  
Daily Ration ◽  
The Mean ◽  
Low Levels ◽  
Lambing Rate

ABSTRACTThe effect on the reproductive performance of Greyface (Border Leicester × Scottish Blackface) ewes of a low level food intake and associated loss of live weight from either 14 days before mating, or from the time of mating, until 11 to 26 days after mating, was investigated. Ewes (252) were allocated to one of three treatments with ewes within each treatment divided into two flocks (flock A: 16 ewes per treatment; flock B: 68 ewes per treatment). Ewes of treatment LL were given a ration providing proportionately 0·5 estimated metabolizable energy (ME) requirements for maintenance from 2 weeks before mating. Those of treatment HL were given a daily ration providing 1·5 estimated ME requirements for maintenance until mating and the restricted ration thereafter. Ewes of treatment HH were given the higher ration throughout the experimental period. Flock A ewes were slaughtered at 11 days post mating and flock B ewes at between 18 and 26 days post mating. Treatment differences in the ovulation rates of flock A ewes were not statistically significant but in flock B, ewes of treatment LL had a lower mean ovulation rate (1·81) than those of treatments HL (2·23) and HH (2·09) (P < 0·001). The lower ovulation rate of LL ewes relative to HL ewes in flock B was reflected in a lower mean potential lambing rate per ewe pregnant than in the HL treatment (1·58 v. 1·79; P < 0·01) and per ewe put to the ram (1·37 v. 1·65; P < 0·01). HL ewes had a slightly lower mean potential lambing rate per ewe pregnant (1·79 v. 1·97; P < 01) and per ewe put to the ram (1·65 v. 1·82; P < 0·05) than HH ewes. Ova wastage rates of LL + HL and HH ewes were 0·26 and 014 (P < 001) respectively at 24 days post mating. Values for LL and HL ewes (0·27 and 0·25 respectively) were not significantly different.Estimated mean conceptus lengths were 370, 500 and 1400 μin for LL, HL and HH ewes respectively (P < 0·05).It is concluded that low food intake before mating reduced the mean ovulation rate and low intakes after mating compromised embryo growth rate and induced a higher rate of ova wastage; this increase in the incidence of ova wastage was not significantly exacerbated by the low levels of intake prior to mating.

Effect of the body condition of ewes on the secretion of LH and FSH and the pituitary response to gonadotrophin-releasing hormone

1989 ◽  
Vol 120 (3) ◽  
pp. 497-502 ◽  
Author(s):  
S. M. Rhind ◽  
S. McMillen ◽  
W. A. C. McKelvey ◽  
F. F. Rodriguez-Herrejon ◽  
A. S. McNeilly
Keyword(s):  
Body Condition ◽  
Luteal Phase ◽  
Body Condition Score ◽  
Pulse Amplitude ◽  
Ovarian Hormones ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
High Body ◽  
Condition Score ◽  
Gonadotrophin Releasing Hormone

ABSTRACT The effects of body fat content (body condition) of ewes on hypothalamic activity and gonadotrophin-releasing hormone (GnRH) secretion and on pituitary sensitivity to GnRH were investigated using Scottish Blackface ewes. Two groups of 12 ewes were fed so that they achieved either a high body condition score (2·98, s.e.m. = 0·046; approximately 27% of empty body weight as fat) or a low body condition score (1·94, s.e.m. = 0·031; approximately 19% of empty body weight as fat) by 4 weeks before the period of study. Thereafter, they were differentially fed so that the difference in mean condition score was maintained. Oestrus was synchronized, and on day 11 of the subsequent cycle half of the ewes of each group were ovariectomized. On day 12, the remaining ewes were injected (i.m.) with 100 μg prostaglandin F2α analogue and ovariectomized 30 h later. Numbers of large ovarian follicles and corpora lutea present at ovariectomy were recorded. Blood samples were collected at 15-min intervals for 12 h on day 10 of the cycle (luteal phase) and at 10-min intervals from 24 to 30 h after prostaglandin injection (follicular phase). At days 2 and 7 after ovariectomy, samples were collected at 15-min intervals for 8 h and ewes were then injected with 10 μg GnRH and samples were collected for a further 3 h. Samples were assayed for LH and FSH. Ewes in high body condition had more more large follicles than ewes in low body condition during the luteal phase (15·3 vs 6·5; P < 0·05) and follicular phase (11·5 vs 7·0; NS) and a slightly higher mean ovulation rate (1·50 vs 1·20; NS). However, during the luteal and follicular phases of the cycle before ovariectomy there was no effect of condition score on mean LH or FSH concentrations or mean LH pulse frequency or pulse amplitude. Two days after ovariectomy, ewes of high body condition had a higher mean LH pulse frequency than ewes of low body condition (P < 0·05) and higher mean FSH concentrations (P < 0·05). Mean LH concentration and pulse amplitude were not affected. LH and FSH profiles were not affected by body condition on day 7. GnRH-induced increases in LH and FSH concentrations on days 2 and 7 were not affected by body condition. At day 7, but not day 2, ewes ovariectomized during the luteal phase of the cycle had a significantly (P < 0·05) greater GnRH-induced LH release compared with ewes ovariectomized during the follicular phase. It is concluded that body condition directly affects hypothalamic activity and GnRH secretion, but not pituitary sensitivity to GnRH, and that effects on reproductive performance are also mediated through changes in ovarian hormones or in hypothalamo-pituitary sensitivity to ovarian hormones. Journal of Endocrinology (1989) 120, 497–502

The effect of weight at mating and of nutrition during mid-pregnancy on the birth weight of lambs from primiparous ewes

1981 ◽  
Vol 97 (3) ◽  
pp. 723-729 ◽  
Author(s):  
A. J. F. Russel ◽  
Janet Z. Foot ◽  
I. R. White ◽  
G. J. Davies
Keyword(s):  
Birth Weight ◽  
Live Weight ◽  
Metabolizable Energy ◽  
Maternal Weight ◽  
Nutritional Treatment ◽  
Condition Score ◽  
Negative Effect ◽  
The Mean ◽  
Pelleted Diet ◽  
Positive Effect

SUMMARYForty-eight approximately 18-month-old Scottish Blackface ewes were used to study the effects of two levels of nutrition during mid-pregnancy (30–98 days of gestation) on the birth weight of lambs from ewes varying in weight, size and condition at first mating. The mean live weight (42–4 kg), size index (31–9) and condition score (2–4) at mating of the 26 ewes from flock A were all less than those of the 22 ewes from flock B (54–5, 39–4 and 2–9 respectively). Mean intakes of the low and high nutritional treatment ewes during mid-pregnancy were 10–6 and 22–0 g/kg/day respectively of a pelleted diet supplying 8–81 MJ metabolizable energy and 125–5 g crude protein/kg. These intakes produced estimated changes in net maternal weight of approximately – 5 and 0 kg respectively.Mean lamb birth weights from ewes on the low and high nutritional treatments were:flock A, 3–32 and 3–83 kg; flock B, 4–96 and 4–23 kg respectively. Analyses showed intake during mid-pregnancy to have a positive effect on lamb birth weight in the flock A ewes, and a negative effect in flock B ewes. Mating weight accounted for 78% of the variance in birth weight in the low nutritional treatment ewes but had little effect in those on the higher level of feeding.The practical implications of the results are discussed in relation to levels of juvenile nutrition.

Unaltered pulsatile and circadian TSH release in euthyroid patients with endemic goitre

1991 ◽  
Vol 124 (4) ◽  
pp. 386-390 ◽  
Author(s):  
Peter Weber ◽  
Ulrich Krause ◽  
Gabi Gaffga ◽  
Georg Brabant ◽  
Friedrich Manz ◽  
...  
Keyword(s):  
Thyroid Volume ◽  
Secretory Activity ◽  
Venous Catheter ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Pathophysiological Role ◽  
Tsh Secretion ◽  
The Mean ◽  
Serum Tsh

Abstract. To evaluate the pathophysiological role of TSH in goitrogenesis we investigated pulsatile TSH secretion in 11 patients with a non-toxic goitre and in 11 healthy controls. Thyroid volume was 40 ± 10 ml in the goitre group and 15 ± 4 ml in the controls as measured by ultrasound. Blood was sampled continously via an indwelling venous catheter at 10-min intervals over 24 h. Neither the mean 24-h serum TSH levels (goitre 1.1 ± 0.5 vs controls 0.9 ± 0.4 mU/l) nor the nocturnal surge of TSH were significantly different between the two groups. The average of the TSH pulse frequency (goitre 10.8 ± 3.7 vs controls 9.6 ± 3.5 pulses/24-h) and of the TSH pulse amplitude (goitre 0.4 ± 0.2 vs controls 0.3 ± 0.1 mU TSH/l as analysed by DESADE programme (detection of secretory activity by discrete deconvolution) did not differ in the two groups. Furthermore, there was no correlation between the volume of the thyroid gland and the dynamics of the TSH secretion. We conclude that our data do not suggest a relevant pathophysiological role of TSH secretion in the development of non-toxic goitre in man.

Circadian, ultradian, and episodic gonadotropin and prolactin secretion in human pseudocyesis

1991 ◽  
Vol 124 (5) ◽  
pp. 501-509 ◽  
Author(s):  
Mary A. Bray ◽  
Ozgul Muneyyirci-Delale ◽  
George D. Kofinas ◽  
Francisco I. Reyes
Keyword(s):  
Time Series ◽  
Pulse Amplitude ◽  
Recovery Phase ◽  
Pulse Frequency ◽  
Prolactin Secretion ◽  
Interpulse Interval ◽  
Hypothalamic Amenorrhea ◽  
The Mean ◽  
Pulse Analysis ◽  
Endocrine Alterations

Abstract. Six women with pseudocyesis were studied by 15-min blood sampling for 12 to 24 h to determine their gonadotropin and PRL secretory profiles aiming to clarify the endocrine alterations in this form of hypothalamic amenorrhea. Clinical and biochemical evidence of hyperandrogenism was found in 4 patients. Persistent hyperprolactinemia was present only in one patient. Significant circadian and ultradian periodicities were identified by time series analysis in the 12-24 h profiles of FSH, LH and PRL secretion. Pulse analysis by the Van Cauter (UL-TRA.JN) method revealed a 24-h mean LH interpulse interval of 91±21 min with a mean LH amplitude of 5.4±0.8 IU/l. There was a significantly lower pulse frequency at night than during the daytime. The mean 24-h PRL interpulse interval and pulse amplitude were 134±22 min and 9.2±1.8 IU/l, respectively. Both FSH and LH mean levels were higher during the daytime than at night, while the reverse was true for PRL values. Decreased LH pulse frequeny and amplitude emerged as the most distinctive findings. Antecedent hypothalamic-pituitary aberrations due to other endocrinopathies and the timing of the hormonal assessment (e.g. recovery phase) may explain, at least in part, the reported heterogeneity of neuroendocrinologic findings in pseudocyesis.

PERIPHERAL PLASMA LEVELS OF OESTRONE, OESTRADIOL-17β AND PROGESTERONE DURING OVULATORY MENSTRUAL CYCLES IN THE RHESUS MONKEY WITH SPECIAL REFERENCE TO THE ONSET OF MENSTRUATION

1973 ◽  
Vol 74 (4) ◽  
pp. 732-742 ◽  
Author(s):  
William T. K. Bosu ◽  
Elof D. B. Johansson ◽  
Carl Gemzell
Keyword(s):  
Macaca Mulatta ◽  
Plasma Levels ◽  
Luteal Phase ◽  
Rhesus Monkeys ◽  
Vaginal Bleeding ◽  
Follicular Phase ◽  
Menstrual Cycles ◽  
Peripheral Plasma ◽  
The Mean ◽  
Low Levels

ABSTRACT The levels of oestrone (E1)*, oestradiol-17β (E2) and progesterone (P) were determined simultaneously by radioimmunoassay in serial peripheral plasma samples from 11 rhesus monkeys (Macaca mulatta) during ovulatory menstrual cycles. In 3 other monkeys luteectomy was performed on day 20 or 21 of the menstrual cycle. The mean plasma levels of oestradiol-17β predominated over the mean E1 during the follicular phase, but during the luteal phase the E1 and E2 patterns varied widely. Before menstruation, increased or unchanged levels of E1 and E2 were mostly found. The decrease found in a few monkeys never reached the low levels found during the days after the midcycle peak. The plasma levels of progesterone increased from less than 0.2 ng/ml during the follicular phase to maximal values within 3 to 4 days after the midcycle peak of oestradiol-17β. The plasma levels of progesterone decreased to less than 1 ng/ml and remained low for 3 to 5 days before menstruation. In the luteectomized monkeys the plasma levels of P, E1 and E2 fell dramatically within 24 h and vaginal bleeding was detected within 72 h post-operatively. In 2 of the 3 luteectomized monkeys the levels of E1 and E2 increased before the bleeding. The ratio of oestrogens (oestradiol-17β and oestrone) over progesterone changed markedly in favour of the oestrogens during the pre-menstrual period. It is concluded that the patterns of progesterone and oestrogens are divergent during the luteal phase. The maximal levels of progesterone are reached early while the maximal levels of oestrogens are reached later during the luteal phase.

Relationships between energy intake, nutritional state and lamb birth weight in Greyface ewes

1977 ◽  
Vol 89 (3) ◽  
pp. 667-673 ◽  
Author(s):  
A. J. F. Russel ◽  
T. J. Maxwell ◽  
A. R. Sibbald ◽  
D. McDonald
Keyword(s):  
Regression Analysis ◽  
Birth Weight ◽  
Energy Intake ◽  
Energy Input ◽  
High Energy ◽  
Metabolizable Energy ◽  
Nutritional State ◽  
Energy Requirements ◽  
Moderate Degree ◽  
The Mean

SummaryIndividual feed intakes of housed mature Greyface (Border Leicester × Scottish Blackface) ewes were adjusted weekly to maintain plasma 3-hydroxybutyrate concentrations during the final 6 weeks of pregnancy at the following values: treatment 1 (adequately nourished; 17 ewes) less than 0·7 mmol/1; treatment 2 (moderately undernourished; 15 ewes) at about 1·1 mmol/1; treatment 3 (severely undernourished; 15 ewes) at about 1·6 mmol/1.The mean energy intakes (MJ metabolizable energy (ME)/day) required to maintain the prescribed nutritional states in single- and twin-bearing ewes were: treatment 1, 14·3 and 16·3; treatment 2, 10·6 and 11·6; treatment 3, 8·1 and 10·0 respectively.The moderate degree of undernourishment had no significant effect on the birth weight of single lambs, but reduced the birth weight of twins by 8·2%, while the more severe undernourishment reduced the birth weights of singles and twins by 21·5 and 25·8% respectively.Foetal energy requirements, estimated by regression analysis, appeared to decrease from more than 2 MJ ME/kg/24 h at 35 days prepartum to 1·54 MJ ME/kg/24 h in the week before parturition.The amounts of energy required to sustain the nutritional states of treatments 1–3 in non-pregnant ewes were calculated to be 348, 271 and 231 kJ ME/kg0.75/24 h, compared with a maintenance requirement, determined in this experiment, of 344 kJ ME/kg0.75/24h.It is concluded that in individually fed ewes a nutritional state characterized by plasma 3-hydroxybutyrate concentrations of 1·1 mmol/1 would constitute an acceptable compromise between an uneconomically high energy input and an excessive reduction in lamb birth weight.

Progesterone acutely increases LH pulse amplitude but does not acutely influence nocturnal LH pulse frequency slowing during the late follicular phase in women

2007 ◽  
Vol 292 (3) ◽  
pp. E900-E906 ◽  
Author(s):  
Christopher R. McCartney ◽  
Susan K. Blank ◽  
John C. Marshall
Keyword(s):  
Time Course ◽  
Phase 1 ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Follicular Phase ◽  
Double Blind ◽  
Phase Cycle ◽  
Significant Difference ◽  
Acute Increase ◽  
Late Follicular Phase

Progesterone (P) is the primary effector of LH (and by inference gonadotropin-releasing hormone) pulse frequency slowing in cycling women, but the time course of this action is unclear. We hypothesized that P administration to estradiol (E2)-pretreated women would slow LH pulse frequency within 12 h. We studied eight normally cycling women in two separate cycles (follicular phase, cycle days 7–11). After 3 days of E2 pretreatment (0.2 mg/day via transdermal patches), a 25-h blood sampling protocol (starting at 0800) was performed to define LH pulsatility. Oral micronized P (100 mg) or placebo (PBO) was administered at 1800 in a randomized, double-blind fashion, with treatment crossover occurring during a subsequent cycle. The 10-h mean P concentration increased from 0.6 ± 0.1 ng/ml before P (0800–1800) to 3.9 ± 0.3 ng/ml after P administration (2200–0800, P < 0.01). Ten-hour mean LH interpulse interval increased significantly after both P and PBO administration, with no significant difference between P and PBO. In contrast, mean LH, LH amplitude, and mean FSH increased significantly within 4 h of P administration, but not after PBO. We conclude that, in E2-pretreated women in the late follicular phase, 1) nocturnal LH pulse frequency is not acutely (within 12 h) influenced by P administration; 2) an acute increase in P causes pronounced augmentation of gonadotropin pulse amplitude within 4 h; and 3) LH pulse frequency slows overnight during the second half of the follicular phase.

Pulsatile thyrotropin and prolactin secretion in a patient with a mixed thyrotropin- and prolactin-secreting pituitary adenoma

1994 ◽  
Vol 130 (2) ◽  
pp. 113-120 ◽  
Author(s):  
Ria Adriaanse ◽  
Georg Brabant ◽  
Erik Endert ◽  
Frederique J Bemelman ◽  
Wilmar M Wiersinga
Keyword(s):  
Pituitary Adenoma ◽  
Medical Center ◽  
Academic Medical Center ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Prolactin Secretion ◽  
Before And After ◽  
Temporal Coupling ◽  
Nocturnal Increase ◽  
The Mean

Adriaanse R, Brabant G, Endert E, Bemelman FJ, Wiersinga WM. Pulsatile thyrotropin and prolactin secretion in a patient with mixed thyrotropin- and prolactin-secreting pituitary adenoma. Eur J Endocrinol 1994;130:113–20. ISSN 0804–4643 The circadian and pulsatile thyrotropin (TSH) and prolactin (PRL) release was investigated in a patient with slight hyperthyroidism due to a mixed TSH- and PRL-secreting pituitary adenoma. Blood was withdrawn every 10 min for 24 h (before and after medical treatment); pulse characteristics were analyzed by Desade and Cluster programs (values as mean±sd). The inappropriately high mean 24-h TSH concentration of 3.55 ±0.31 mU/l was associated with a higher mean 24-h TSH pulse amplitude but unaltered mean 24-h TSH pulse frequency relative to healthy controls. The nocturnal TSH surge (absolute surge 0.5 mU/l, relative surge 16%) was low, related to a loss of the usual nocturnal increase of TSH pulse amplitude and TSH pulse frequency. Chronic treatment with octreotide resulted in a modest clinical and biochemical improvement of the hyperthyroid state; addition of bromocriptine at a later stage had no further beneficial effect. At the end of the follow-up period the mean 24-h TSH paradoxically had increased to 5.33 ±0.81 mU/l. The nocturnal TSH surge also increased (absolute surge 1.9 mU/l, relative surge 42%), but circadian changes in TSH pulsatility remained absent. In the untreated period the increased mean 24-h PRL concentration of 234 ± 24 μg/l was associated with an increased mean 24-h PRL amplitude, whereas the 24-h PRL pulse frequency (N = 4) was lower relative to controls. No circadian PRL rhythm was present. After octreotide and bromocriptine treatment the mean 24-h PRL concentration and mean 24-h PRL pulse amplitude were unchanged, but a clear nocturnal increase of PRL now was observed. Analysis of the temporal coupling between TSH and PRL release by bivariate autoregressive modeling revealed significant cross-correlations in all three periods investigated (coefficients in the range 0.34–0.76, median 0.52; p<0.01) between TSH and PRL concentrations with a lag time of 10–20 min. We conclude that pulsatile TSH and PRL release in this mixed TSH- and PRL-secreting pituitary adenoma was autonomous in nature. The observed dampening of the nocturnal increase of TSH and PRL is putatively related to a lack of TRH receptors in these tumors. The observed co-secretion of TSH and PRL suggests synthesis of both hormones by the same cell. R Adriaanse, Department of Endocrinology F5-171, Academic Medical Center, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands

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