Anterior Lobe Extracts Research Articles

EFFECTS OF THE INTRODUCTION OF BLOOD FROM BRED RABBITS UPON IMMATURE RABBITS *

As was first pointed out by Heape (1) and verified by Hammond and Marshall (2) ovulation in the rabbit occurs normally ten to twelve hours following copulation. The work of Evans (3) on the luteinizing effect of anterior lobe extracts upon rat ovaries, and that of Smith and Engle (4) and Zondek and Aschheim (5) on the gonad-stimulating effects of the anterior lobe, as well as that of Smith (6) showing that hypophyseetomy caused cessation of the oestrus cycle in the rat all indicated a relationship existing between the anterior lobe and the ovary. Bellerby (7) working with hypophyseal extracts and Friedman (8) working with pregnancy urine were able to induce ovulation in the unbred rabbit and Fee and Parkes (9) have demonstrated that hypophyseetomy within one hour following copulation prevents ovulation. This, in broad outline, is the evidence for the belief now commonly held, that ovulation in the rabbit is the end product of two reactions: first, an activation of the anterior lobe probably by means of th...

STUDIES ON THE PHYSIOLOGY OF LACTATION. III. THE RECIPROCAL HYPOPHYSEAL-OVARIAN RELATIONSHIP AS A FACTOR IN THE CONTROL OF LACTATION†§

Investigations during the past few years by Strieker and Giuter (1929), Corner (1930), Nelson and Pfiffner (1930–31), and Turner and Gardner (1931) have established the relation of the anterior hypophysis to the induction of lactation. These various studies have shown that the mammary glands must be developed under the influence of the ovarian hormones before the anterior lobe factor can initiate secretory activity. The degree of development of the glands which is necessary before lactation may be induced and the relative importance of the two ovarian hormones, oestrin (theelin) and progestin (corporin), in the production of gland growth varies in the different species of animals examined. However, it seems definitely established that the mammary glands of any animal must have attained at least the condition present in the adult female of that species before lactation may be induced by the administration of anterior lobe extracts.

Studies on the hypophysectomized ferret. VIII. -Effect of administration of anterior lobe extract, prolan, and the two combined

A number of workers have reported on replacement therapy in hypo-physectomized animals. Cushing (1912) found that pituitary transplantations prolonged the life of hypopsectomized dogs. Smith (1927) studying rats showed that the characteristic disabilities arising from hypophysectomy in rats could be completely, or almost completely, relieved by daily pituitary implants. On the other hand, intraperitoneal injections of saline extracts not only did not restore the atrophied sex organs, but prevented their repair by the pituitary implants, Putman, Teil and Benedict (1928) stated that growth was restored in hypophysectomized dogs and rats by alkaline extracts of pituitary tissue. Reichert (1928) reported successful replacement therapy in an hypophysectomized puppy with daily fresh heterotransplants of rabbit pituitary, and in a later paper (1929), growth in hypophysectomized puppies exceeding that of normal controls, after administration of Evans' extract. Reichert and others (1932) described prolan (pregnancy urine extract) as being ineffective in three hypophysectomized dogs and one rat. More recently Collip and others (1933, a, b, c ) have reported tire results of placental extracts on a large number of hypophysectomized rats. They confirmed Smith's earlier Endings (1927) and also stroked that tire response of tire hypophysectomized female rat to A. P. L. is conditioned by the state of the ovary at the time of operation. The placental material was found to lead to thecal luteinization both in the prepubertal and in the hypophysectomized animal, a conclusion reached earlier by Noguchi (1931). Collip and others were able to obtain follicle maturation and corpus luteum formation in hypophysectomized female rats by tire combination of A. P. L. and certain extracts of pituitary, and they assume that a "complementary substance" is furnished by the pituitary which cooperates with the placental substance in its action on the ovary. In two recent papers Smith and Leonard (1933) and Leonard and Smith (1933) have studied the action of a pregnancy urine extract in hypophysectomized male and female rats. In the male they obtained a beneficial effect on spermatogenesis as a result of treatment, and in the female a cornified vaginal smear and enlargement of the ovaries, which, however, decreased with continued injection. In recently operated animals there was hypertrophy of the interstitial cells and development of new corpora lutea where treatment was postponed some interstitial hypertrophy and often corpora lutea formation occurred. The present paper deals with results of treatment of 7 hypophysectomized ferrets with: (1) an anterior pituitary extract; (2) pregnancy urine extract; and (3) the two combined.

THE PRODUCTION OF DECIDUOMATA IN IMMATURE RATS BY PITUITARY TREATMENT1

Deciduomata were produced in immature rats which received gonadal stimulation with anterior pituitary implants and subsequent injections of basic extracts of beef anterior lobe (Shelesnyak, 1931). During the treatment with basic extract, the uteri of the experimental animals were stimulated by tying thread loops through the lumen after the method of Long and Evans (1922). The decidual reaction was uniformly positive. A control series of rats, which was treated similarly, except that a small amount of oestrin (Amniotin, Squibb) was substituted for the pituitary implants, in general failed to show the reaction. Only two cases suggested any decidual cell response. The present investigation deals with some of the probabilities involved in the failure of the reported control series (1931), and attempts to approximate a minimal physiologic sensitization which would enable a stimulated uterus to form deciduomata. It can be seen from earlier work (Weichert, 1928; Hisaw and Leonard, 1930; Leonard, Hisaw and Fevold...

THE RELATION OF THE ANTERIOR PITUITARY TO CARBOHYDRATE METABOLISM*

At the meeting of the American Physiological Society, April 11, 1933, we made a report on this subject which may be summarized as follows:(1) Spontaneous glycosuria had not been observed in a hypophyseetomizedpancreatectomized dog but glycosuria could be produced at will by injection of anterior lobe extracts. (2) Glycosuria had been produced in normal dogs by injection of suitable anterior pituitary extracts. (3) These same extracts did not produce glycosuria in a thyroidectomized dog. At this time we wish to report the details and extension of these experiments. The experimental evidence for an interrelationship between the anterior hypophysis and carbohydrate metabolism will be briefly considered under three divisions, (1) hypophysectomy, (2) hypophysectomy and pancreatectomy, and (3) injection of anterior lobe extracts. The most striking changes in carbohydrate metabolism after hypophysectomy are (1) sensitivity to insulin (Houssay and Magenda, 1924; Geiling. et al., 1927) and (2) hypoglycemic convuls...

The Effects of Hypophysectomy and Anterior Lobe Administration on the Skin and Thyroid of Triton Cristatus

ABSTRACT The skins of many vertebrates react to variations in the amount of hormones of the endocrine glands, especially of the thyroid and pituitary. Moulting in Triturus viridescens is inhibited after both thyroidectomy and hypophysectomy or both operations simultaneously performed. The cornified layers continue to form and the accumulation of these makes the animal appear grimy (Adams and Richards, 1929; Adams, Richards and Kuder, 1930; Adams, Kuder and Richards, 1932). The series of experiments here reported demonstrates that a similar effect occurs after hypophysectomy in immature or mature Triton cristatus (Adams, 1931a). The moult in Triturus viridescens operated in the above ways can be induced by various methods. Supplying thyroid hormone by thyroid grafts or thyroxin injections, or administering iodine to thyroidectomised or hypophysectomised animals or to ones lacking both glands, or stimulating the thyroid glands of hypophysectomised animals either by giving pars anterior grafts or injections or by pinching them in situ, will cause the shedding of the cornified layers (Adams et al. 1930, 1932; Adams, 1931 b, 1932). Similarly in hypophysectomised Triton cristatus, the moult can be induced by administration of pars anterior substance or by injection of certain extracts of mammalian anterior lobe.

Effect on Ovarian Weight of Prolonged Administration of Anterior Lobe Extract.

It was shown that the administration of a pregnancy blood, extract at daily doses which produce comparatively small increases in ovarian weight (100 to 200%) in 5-day experiments, results in very marked enlargement of the ovaries if the injections are continued for from 2 to 3 weeks. These studies have been extended to include the effects induced by an extract prepared from dried sheep anterior hypophyses by the method of Wallen-Lawrence and Van Dyke. This procedure is essentially the same as that used for preparing the pregnancy blood extracts and consists in extracting with a sodium acetate-acetic-acid buffer, pH 4.2 to 4.5, and reprecipitating with 95% alcohol. A total of 78 rats have been treated for periods up to 20 days in duration and with various doses of the extracts. The experiments were begun in animals 20 to 23 days of age, and each rat was injected twice daily. It has been observed that when immature female rats are given daily injections of sheep anterior pituitary extract in such doses that the ovaries increase from 100 to 500% in weight in the first 5 days, the continued daily administration of the same dose for periods up to 20 days fails to produce any further marked increase in ovarian weight. For instance, in one series of 21 rats each animal was given 0.5 cc. of a comparatively weak extract daily and groups of 5 or 6 were sacrificed every 5 days. The average percentage increase in ovarian weight over controls on the 5th day was 420% (body weight 33 gm., ovaries .060 gm.). On the 10th day it was 375% (body weight 47 gm., ovaries .054 gm.); on the 15th it was 462% (body weight 60 gm., ovaries .078 gm.), and on the 20th it was 412% (body weight 63 gm., ovaries .073 gm.).

Note on the Failure of Anterior Lobe Extract to Pass from Fetus to Mother.

In a previous paper we showed that ovulation can be induced in the pregnant rabbit by intravenous injection of concentrated human urine of pregnancy or anterior lobe extract of beef. This observation was the basis of further experiments here reported. Since a pregnant rabbit could be made to ovulate by injecting either of these substances, it appeared that this phenomenon might well be used to investigate the possibility of the passage of anterior lobe substance from fetus to mother. We used 6 pregnant rabbits. The rabbits were opened under ether anesthesia by laparotomy. The injections were made through the unopened uterus directly into the fetuses by the aid of a syringe and a fine gauge needle. In all instances the material was injected into the peritoneal cavity or the neighboring musculature of the rump of the fetus. Into a fetus in one rabbit we injected 1 cc. of concentrated human urine of pregnancy. Into the fetuses in the other 5 rabbits various amounts from 2 to 8 cc. of anterior lobe extract (beef) were injected. Two days later the mother was opened again under anesthesia, so that the ovaries could be examined. At the same time the fetuses were observed to see that they were still living and their circulation intact. In the observations reported, all of the fetuses were alive at the termination of the experiments, so that failure of the anterior lobe extract to cause ovulation in the mothers can not be attributed to fetal death. The results are shown in Table I. In no instance did ovulation occur in the mother after injection of anterior lobe extract into the fetuses. The series is small, but in 3 instances relatively large amounts of anterior lobe extract were injected into the fetuses.

Uterine Bleeding of the Interval Type in Macacus Monkey During Injections of Extracts of Pregnancy Urine.

Uterine bleeding in the spayed or immature macacus monkey is known to occur from an interval type endometrium about 6 days after cessation of an adequate treatment with oestrin (Theelin, Allen1, Maddux2;) (Amniotin, Morrell et al.3). These observations have been repeatedly confirmed in this laboratory. Uterine bleeding in the adult also occurs after bilateral ovariectomy (Allen; Van Wagenen and Aberle4) or occasionally after unilateral ovariectomy (VanWagenen and Aberle). (Uterine bleeding indicates a hemorrhage of uterine origin macroscopically visible on the external genitalia of the monkey, but which may not be homologous with menstruation). Saiki5 has shown that uterine bleeding may be induced in immature macaques 4 to 9 days after the cessation of 8-17 days treatment with an extract of anterior lobe (P. D. & Co.). Our work confirms these results. However, if water soluble extract of pregnancy urine or the “luteinizing hormone” (P. D. & Co.) be administered in adequate doses for from 19 to 22 days, in...

Quantitative Difference in a Rabbit-Ovulating Dose of Prolan and Anterior Pituitary Extract

Conclusions1. The ovulating dose of an anterior pituitary extract for rabbits is very much less than that of Prolan when the potency of these 2 substances is standardized on immature female rats. 2. This difference in quantitative activity of Prolan and anterior lobe extract suggests a physiological difference between the 2 substances.

Homology of Prooestrous Bleeding in the Dog

The prooestrous uterine bleeding of dogs and menstruation of primates have been considered by some physiologists to be very similar and to represent in 2 classes of mammals the result of similar causative factors. (Heape, Marshall.) We have obtained data from experiments conducted on dogs which we believe strongly indicate that the prooestrous bleeding of the dog is not homologous with the menstruation of primates. The evidence for this belief is as follows: (1) Ovariectomy of 5 dogs in the metoestrous phase did not result in external or profuse microscopical bleeding. In all 5 cases microscopical bleeding occurred as early as the 7th day and as late as the 16th day after ovariectomy. This bleeding was only of one or 2 days' duration. No external or microscopical bleeding was observed after ovariectomy of one immature dog and one dog in oestrus. Ovariectomy of monkeys results in external bleeding of about the same quantity as that seen at the normal menstrual period. (E. Allen; Morrel et al; Saiki, in press.) (2) Injection of alkaline extracts of the anterior lobe of the hypophysis which contained the gonad stimulating hormones into 2 dogs with ovaries intact resulted in external bleeding during the period of injection. This bleeding stopped soon after the injections had been discontinued. In monkeys profuse microscopical or external bleeding does not occur during the injection period. A latent period of some days intervenes between the cessation of injection and the appearance of blood. (Hartman; Saiki, in press.) (3) Control experiments in which castrated dogs were injected with quantities of the anterior lobe extracts sufficient to produce external bleeding in the intact animal did not result in profuse microscopical or external bleeding.

Studies on the Pituitary

ABSTRACT The principal facts presented in this communication may be summarised as follows: Removal of the pituitary gland or of the anterior lobe alone results in involution of the ovaries, lowering of the serum calcium and cessation of skin secretion.Ovulation and skin secretion can be induced in Xenopus by injection of extracts of the pituitary gland. This communication has raised a number of issues which would have been investigated more extensively if circumstances had not forced two of the authors to leave South Africa. It is therefore advisable to bring into sharper relief the two most important conclusions which are justified by the facts recorded. The first of these is the very conclusive and complete evidence in support of the view that the anterior lobe of the pituitary controls the activity of the ovaries. Zondek and Ascheim (1927), Smith and Engle (1927), Bellerby (1930) and Parkes (1930) have shown that anterior lobe extracts or transplants stimulate the development of the ovaries in mammals. Unfortunately the removal of the pituitary gland in mammals is an operation of extreme difficulty. Conclusive evidence that the pituitary has a functional relation to the ovaries is lacking, unless the effects of operative removal can be brought into harmonious relationship with the effects of injection and implantation. In Xenopus it is possible to do this in a very striking manner. It is now therefore justifiable to assert that the results obtained by injection and implantation in mammals are not merely an indication of a new and specific pharmaco-dynamic constituent in the anterior lobe of the pituitary gland but of a genuine functional influence of the pituitary on the normal ovarian cycle. The new evidence presented in this communication reinforces a large volume of previous work on the comparative physiology of the ductless glands pointing to a widespread uniformity of endocrine phenomena within the vertebrate series. The other conclusion of outstanding importance which emerges from the present study is the influence of the pituitary gland on calcium metabolism. This opens up a field for further research and it would be premature to discuss it except in a very tentative way. Although there is no evidence at present to indicate that the pituitary gland exerts its influence on calcium metabolism directly, two considerations indicate that the influence of the anterior lobe on serum calcium is independent of the ovary. One is a comparison of the figures given for the eyeless and seeing groups in Table II which summarises the data presented in Sections II and III. The other is that Mirvish and Bosman (1927) have shown that injection of ovarian extracts lowers the serum calcium of rabbits.

Studies on ovulation

The Journal of PhysiologyVolume 71, Issue 1 p. 36-39 ArticleFree Access Studies on ovulation IV. Induction of ovulation in the hypophysectomized rabbit by administration of anterior lobe extracts Margaret Hill, Margaret HillSearch for more papers by this authorA. S. Parkes, A. S. ParkesSearch for more papers by this author Margaret Hill, Margaret HillSearch for more papers by this authorA. S. Parkes, A. S. ParkesSearch for more papers by this author First published: 21 January 1931 https://doi.org/10.1113/jphysiol.1931.sp002715Citations: 6AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume71, Issue1January 21, 1931Pages 36-39 RelatedInformation

Biological and Chemical Studies of Extracts of the Anterior Lobe Pituitary

ABSTRACT A buff-coloured precipitate is obtained by the addition of N/20 iodine solution to dilute acetic acid extracts of fresh anterior lobe substance. The volume of the precipitate depends upon the volume of the iodine solution added. Similar acetic acid extracts of tissues and extracts of the anterior lobes prepared with other extracting media do not give the same precipitate with iodine. The precipitate indicates the presence and, within limits, gives an approximate measure of the metamorphic factor in fresh gland extracts of the anterior lobe. Dilute acetic acid extracts of the precipitates after removal of the iodine by shaking with alcohol are biologically active and characterised by their phosphate content. Similar extracts of the posterior lobe give an iodine precipitate but the phosphate content is much lower than that of the anterior lobe precipitate. The iodine in these precipitates is adsorbed or loosely combined. The adsorbed iodine is chemically more reactive than dissolved iodine or iodine crystals giving rapid evolution of nitrogen from sodium azide compared with the failure of the others. The biological activity of anterior lobe extracts varies with the time of extraction and the concentration of the extracts. There is a maximum for the time of extraction at any particular concentration and acid strength after which a loss of potency occurs. There is a continuous extraction—rapid at first—of the melanophore stimulant. The amount increases with the period of extraction and concentration, but is independent of the strength of the acid used in extraction. The metamorphic factor is slowly destroyed by pepsin but rapidly by trypsin. The biological activity is diminished by boiling, or by boiling with dilute hydrochloric acid, sodium hydroxide, or sodium carbonate.

Effects of Gonad Stimulating Extracts on Basal Gaseous Metabolism in Rats.

Reiss and Winter,1 using extracts containing the sex maturity stimulating principle from the urine of pregnant women, found no constant effects on the oxygen consumption, carbon dioxide production or respiratory quotient in rabbits. They used anesthetized animals, however, gave enormous doses, 200 to 4000 units of the material subcutaneously and followed the metabolism for only a few hours after each injection. We have used what are presumably more physiological doses, without anesthesia, and have followed the metabolic level during and after periods of continued daily administration.Two sources of the sex maturity or gonad stimulating principle were used. One was an extract of sheep anterior lobe∗ and the other we prepared from the urine of women in the first half of pregnancy after the method of Biedl.2 The potency of the extracts used was assayed by testing on infantile rats. Twelve rats were used, 9 females and 3 males. Twenty determinations made in the first 1 to 4 hours following the subcutaneous ad...

Growth and Bone Changes in Rats Injected With Alkaline Anterior Pituitary Extracts.

Some 175 rats, ranging in weight from 30 to 350 gm. were employed in testing the potency of alkaline anterior pituitary lobe extracts over short periods of time. The method of preparing the extract as described by Evans and Simpson1 was adopted. In rats weighing between 30 and 100 gm. the presence of the growth hormone could not be detected. However, in animals weighing from 175 to 300 gm., growth stimulating powers were observed. With animals 200 to 225 gm. in weight, after 12 days of injection (the dose being 1 cc. daily intraperitoneally) the experimental rats gained at an average of 2.1 gm. per diem over the control rats. After 14 days of treatment with 1 cc. doses intraperitoneally daily, injected animals weighing between 250 and 300 gm. gained remarkably in weight, averaging 2.7 gm. daily over the control animals.Periosteal bone growth studies of rats were made by including madder in the diet. Madder was shown by Kolliker to be deposited only in zones of osteoblastic activity, staining newly growing...

Effects of Combined Administration of Extracts of Anterior Lobe of Pituitary and of Potassium Iodide on Thyroid Gland

In former investigations from this laboratory Loeb,1 Gray2 and Rabinovitch3 have shown that potassium iodide may exert, a stimulating effect on the thyroid gland of the guinea pig. It does not prevent compensatory hypertrophy, but may modify its character; in the normal gland it may increase the mitotic activity as much as 40-60 times, and quite commonly increases it 20 times. Furthermore, it produces a slight increase in the size of the acinus cells and a slight softening of the colloid and a very marked increase in the number of phagocytes in the colloid. Loeb4 has shown that oral administration of anterior pituitary substance (Armour & Co.) prevents compensatory hypertrophy of the thyroid gland and McCordock5 has shown that it prevents the hyperplasia caused by potassium iodide. However, if instead of oral administration of anterior pituitary we give daily subcutaneous injections of either acid or alkaline extracts of anterior pituitary, no inhibition of the thyroid gland results, but, on the contrary,...

Basal Gaseous Metabolism of Giant Rats

Gigantism can be produced in rats by the administration of extracts of the anterior lobe of the pituitary. We have determined the basal gaseous metabolism in 4 such giant rats and have compared their metabolic rates with those of 4 control females of the same age and the same Wistar strain. The rats were approximately 11 months old at the beginning of the metabolism determinations. Since the age of 7 months, each of the experimental animals had received daily parenteral injections of 1 cc. of a neutralized alkaline extract of fresh beef anterior lobe containing the growth promoting principle. During the period of the metabolism determinations the weight range of the injected rats, before being starved, was from 350 to 530 gm. The largest of the control rats were selected in order to obviate as much as possible the effect of size per se on metabolism. Their weights ranged from 200 to 270 gm. The increased size and weight of the injected animals is apparently due to the greater bone, muscle and skin development and to the considerable increase in size of most of the viscera, especially the liver. Body fat does not appear to be increased. Despite the obvious general overgrowth, the body lengths of the injected rats averaged less than 10% more than those of the controls. Metabolic rate determinations were made by the oxygen consumption closed circuit method at weekly intervals. Each determination represents the average rate, in several tests, over a 3 to 4 hour period, and 18 to 22 hours after the last ingestion of food. All tests included were considered satisfactory from a technical standpoint. Body surface was calculated from the formula Rat 62 was sacrificed for direct measurement of the skin area, which was found to be only 4% greater than that predicted by the formula. Respiratory quotients were found to be nearly 0.72 in both the injected and control starved rats.

Anterior Lobe Substance, the Thyroid Stimulator. IV. Effect in the Absence of Thyroid Gland.

Spaul reported that injections of anterior lobe substance induced metamorphosis in thyroidectomized axolotls. According to our work, however, the effects of the hormones are quite different and anterior lobe cannot replace the thyroid hormone. To test our claim 6 larvae of the Utah axolotle were most carefully thyroidectomized. As complete thyroidectomy of salamander larvae is very difficult and regeneration of remnants not visible under the dissecting microscope takes place frequently, the injections of an anterior lobe extract prepared in our laboratory, as described in Article 1 of this series, were started in 4 of the thyroidectomized larvae immediately (one day) after the operation. Two normal control larvae of the same stage and approximately same size were injected at the same time with the same sample of anterior lobe powder as the experimentals. Both controls metamorphosed after the sixth injection, 11 days after the first injection. None of the experimentals showed even a sign of metamorphosis after the ninth injection, fifteen days after the first injection. The injections were stopped after the ninth injection; 51 days after the first injection, the experimentals are still completely larval.

Comparative Studies of Accelerated Amphibian Metamorphosis

ABSTRACT The administration of active anterior lobe extracts in solution is not effective in producing precocious transformation of tadpoles. The rate of metamorphosis induced by injection of either thyroid or anterior pituitary depends within limits on the concentration of the initial dose. The time for completion with thyroid depends upon the total quantity given—a cumulative effect. The repetition of the stimulus given by a dose, the quantity per dose having maximum and minimum values, at suitable intervals decides the time of completion with anterior pituitary. Susceptibility of tadpoles to metamorphosis inducing factors increases with age. The effects produced by iodine in metamorphosis (mortality, reduction in size and shrinkage) agree more closely with those obtained in thyroid than pituitary treatment. There is a differential response of certain tissues to concentrations of the thyroid but not to anterior pituitary. Exposure of tadpoles to X-rays alters the susceptibility to factors accelerating metamorphosis. The effect increases with age. Alcohol and potassium cyanide lower the response to thyroid and anterior pituitary stimulation according to the concentration and the age of tadpoles. Normal rates of change are produced by thyroid and anterior pituitary in tadpoles under narcosis. The mortality is slightly higher with thyroid and depends on the concentration of the anaesthetic. Prolonged narcosis reduces the rate of change. Precocious metamorphosis is not found in tadpoles after feeding lipón the endostyle of Ciona intestinalis. The relation to iodine, quantitative and qualitative responses of tadpoles to treatment, and the differential tissue response serve to differentiate between the metamorphic principles of the thyroid and anterior pituitary.