Papillary Carcinoma

It is more common in patients with a history of exposure to radiation and spreads through the lymphatic. You may find lateral aberrant thyroid remnants that are actually occult metastases with a benign histological appearance. These well-differentiated carcinomas may be TSH-dependent and may develop in the context of goiters secondary to Hashimoto’s thyroiditis. Many papillary carcinomas contain follicular elements, but this does not change the basic biology of the tumor.

Therapy
The treatment of small tumors (<1.5cm) encapsulated and localized in one lobe is usually in the lobectomy, although some experts recommend a more extensive surgical treatment. Thyroid hormones in the TSH suppressive doses are administered to minimize the possibility of a new growth or induce regression of any residual microscopic papillary carcinoma, surgical treatment is almost always decisive.

The large tumors (> 1.5 cm) or widespread often require total or subtotal thyroidectomy with postoperative radioiodine scintigraphy and subsequent ablation of residual thyroid tissue with sufficiently high doses of 131 I administered when the patient is hypothyroid . Alternatively, it can be administered recombinant TSH (not yet available) for 2 days before 131 I diagnostic scan performed to detect residual thyroid tissue or tumor, thereby avoiding the need to become hypothyroid patients before scintigraphy itself. May be necessary to repeat treatment every 6-12 months to achieve complete ablation of residual thyroid tissue. After treatment are TSH-suppressive doses of L-thyroxine and determination of serum thyroglobulin is useful for detecting the recurrence or persistence of the disease.

• Inability of the thyroid gland to provide the amount of hormone needed to require the agency at some point.
• The decrease in hormone levels will lead to hyper-secretion of TSH, which will cause an enlargement of the gland.

Causes:

• Iodine deficiency
• Partial deficiency in thyroid hormones
• Using drugs that block the conversion of iodine (eg lithium) or certain foods (cabbage, rape)

Epidemiology:

• More common in women
• Depending on their frequency in a given population, it is called endemic goiter and sporadic.
• Endemic goiters occur in certain regions of the world generally have a deficiency in iodine (eg mountainous regions)

Clinic:

• No functional sign
• No metabolic disorder
• Increase the volume of the neck with or without cervical lymphadenopathy (often a sign of malignancy)
• Sometimes dysphonia, dysphagia, dyspnea, collateral circulation in case of local compression.

Investigations:

• Normal hormonal assays
• The measurement of serum calcitonin plasma eliminates the possibility of medullary carcinoma of the thyroid developed at the expense of cells C.
• A ultrasound: diffuse goiter, homogeneous volume variable that will determine the need for treatment

Treatment:

• No treatment for simple goiter
• If it is large, scalable, there are prescription hormone by levothyroxine, but this treatment should be followed for life.
• If goitre is important surgery.

Evolution:

• Possible exacerbations (at puberty, menopause, pregnancy),
• Over the years, it becomes multi-nodular.
• Possibility of development of carcinoma in goiter

Complications:

• Hyperthyroidism
• Signs of compression of the trachea, respiratory
• Development of cancer with increasing volume of goiter, change its texture (decrease mobility, signs of cuts or cervical lymphadenopathy).

2 – Nodules:
Definition:

• Abnormal production that gives the sensation of touch u hard body more or less rounded and well circumscribed.
• They are routinely discovered by the patient or his environment or during a medical examination.
• They are nodules that increases with swallowing, they are of thyroid origin.
• Epidemiology:
  In 20% cases were thyroid adenoma
  In 10% cases, there is the notion of malignancy

Clinic:

• Hard consistence, Cyst or Cancer
• Soft consistency: benign
• Sometimes dysphonia

Examinations:

• Ultrasound detects nodules fluid (cysts)
• The scan class nodules in 3 varieties:
• hot: fix iodine more intense, benign
• Isofix: fix the radio-active iodine
• hypofixation (cold): absence of iodine uptake
• The ENT examination visualizes the vocal cords for a differential diagnosis
• Aspiration cytology

Treatment:

• Different as appropriate
• If it is a cold nodule, surgery to avoid missing a cancer.

• before puberty, it causes the persistence of infant genital tract, absence of puberty, obesity;
• After puberty, it causes regression of the genital tract, mitigation of secondary sexual characteristics, the suppression of reproductive function cycle arrest genital obesity.
• The administration of ovarian hormones corrects the effects of castration. At excessive doses, they cause the child early development of the genital tract and its annexes.

The ovary secretes four groups of hormones estrogen, progesterone, a small amount of androgens and the group of inhibin and cybernines. Unlike other hormones, inhibin and cybernines are not steroid.

Estrogens.
They are three in number, produced by cells of the theca interna; estradiol, the most active, estrone and estriol
Their physiological actions are as follows;

• actions on the reproductive tract and sexual characteristics;
• they lead hypercontractility horns;
• at the uterine body, they promote the development of uterine muscle and endometrium;
• in the vagina, they cause the appearance on the smear of surface cells;
• in the breast they cause hypertrophy of the mammary gland;
• metabolic actions, estrogen promotes the calcium binding protein on the frame of bone and lean early growth plates. They also promote fluid retention (hence problems with osteoporosis at menopause);
• other actions in women, estrogen facilitates the development of fibroids and cancers of the breast in humans, they cause atrophy of sex organs (penis, epididymis, seminal vesicles), a decrease of spermatogenesis and production testosterone.

Estrogens, partly destroyed by the liver, are mainly excreted through urine as estriol.

Progesterone.
It is developed outside of pregnancy by the granulosa cells (yellow body), and during pregnancy by the placenta.
The physiological role of progesterone focuses on the preparation and maintenance of pregnancy and the destruction of the corpus luteum in early pregnancy leads to stop it.
It exerts its action;

• genital tract;
• level of the uterus, it softens the muscle where it inhibits uterine contractions, and it complements the action of estrogens on the mucosa.
• in the vagina, it changes the appearance of smears (the appearance of cells Plicata);
• in the breast, she enlarged mammary glands;
• during pregnancy, it inhibits the contractility of the uterus and prevents the expulsion of the ovum.
• Other activities: it facilitates the metabolism of estrogen and has an elevation of temperature.

Progesterone is excreted in urine as pregnanediol.
It now manufactures synthetic progestins, which, by blocking ovulation, are used for contraceptive purposes.

Androgens.
The ovary secretes a small amount of androgen secreted primarily by the ovarian stroma.
They act primarily on the pubic and axillary hair.

Inhibin and cybernines
The ovarian inhibin has similar actions at the pituitary and hypothalamus that testicular inhibin. In the ovary, inhibin is involved in follicular maturation.
Cybernines modulate the actions of FSH and LH in the follicle. Several cybernines are currently known:.
The study of ovarian hormones showed some secretory specialization of the different constituents of ovarian parenchyma since:

• the theca cells secrete estrogen;
• the granulosa cells secrete progesterone, inhibin and cybernines;
• Finally, the stromal cells develop ovarian androgens.

The ovarian hormone cycle.
From the first to fourteenth day cycle: follicular maturation occurs under the influence of FSH secreted by the pituitary gland. The secretion of pituitary FSH is itself triggered by a hypothalamic control center that develops a hormone called LHRH. which stimulates the pituitary secretion. The hypothalamic control center has a cyclical activity and its secretion is dependent on circulating estrogen levels and the secretion of inhibin and cybernines.
As and when the maturation of the follicle, its cells secrete estrogen which increases the rate throughout this period. Estrogens cause changes in uterine and vaginal mucous membranes studied in the previous chapter. They also act on LHRH secretion which in turn causes the secretion of pituitary LH;
In the fourteenth day of the cycle, the secretion of pituitary LH peaked determines spawning ovular;
During the second half cycle, the activity of the corpus luteum is controlled by the pituitary gland secretion of F. SH is lower and the LH is dominant, taking under its control hormonal secretion of the corpus luteum. It simultaneously secretes estradiol and progesterone and the association controls the transformation of endometrium (uterine lace) and vagina. The closure of these different hormonal secretions marks the end of the cycle and the onset of the rules. Atrophy of the corpus luteum is under periodic dependence of inhibitor binding LH receptors.
During the second half cycle, there is also a secretion of pituitary prolactin explains congestion premenstrual breast but does not affect the course of the ovarian hormone cycle. In contrast, during pregnancy, prolactin secretion increases dramatically which determines the changes of pregnancy-the mammary gland and, subsequently, postpartum lactogenesis.
The onset of ovarian activity occurs at puberty in hypothalamic-pituitary control, and that the emergence of endocrine secretions of the ovary is responsible for changes in the reproductive tract and the appearance of characters secondary sex.
The cessation of ovarian endocrine activity takes place about fifty years it is menopause.

Adrenocortical hormones
The cortex secretes many hormones whose chemical composition is now well defined and their manufacture in the adrenal (biosynthesis) and their metabolism in the body. The physiological action of some compounds is however still unknown.



All adrenal hormones can now be synthesized and it makes even artificial products endowed with hormonal activity but radically different structure of natural hormones (called steroid synthesis).
All the hormones of the adrenal cortex is known as the General corticosteroids or steroids.
All these hormones have in common the same core chemical sterol nucleus and the same synthetic pathway, ie manufactured from cholesterol; different hormones differ only by elements fixed on the nucleus;
The hormones of the adrenal cortex may, depending on their biological role, be classified into three major groups: mineralocorticoids, glucocorticoids and androgens.

Mineralocorticoids.
These are the hormones of water and salt. They regulate the body effect in the balance of water and electrolytes by acting on the disposal of this material by the kidney. The hormone essential for this group is called aldosterone, it reduces the renal elimination of sodium and water and increases the contrary the elimination by the body, potassium, and the point of impact hormone is the distal renal tubule: it increases at this level, the reabsorption of sodium and water and increases the secretion of potassium. Adrenalectomy causes so because of the suppression of secretion of aldosterone an increased urinary excretion of sodium and water retention and potassium: these disturbances result clinically by polyuria, dehydration, hypotension and biologically by lower blood levels of sodium, chlorine, alkali reserve and elevated potassium. Conversely, an excessive secretion of aldosterone has been demonstrated in some adrenal tumors (hyperaldosteronism or Conn’s syndrome), then there is high blood pressure, fatigue, muscle weakness, tetanic seizures, and biologically, a decrease of blood potassium (hypokalemia), elevated blood sodium (hypernatremia), reserve alkaline (metabolic alkalosis), blood volume (blood volume), increased urinary excretion of potassium (hyperkaliurie ), a decrease of sodium (hyponatriurie). Other hormones of this group have a lower action than aldosterone, these are: the deoxycorticosterone and 17 hydroxy 11 deoxycorticosterone. At its action on metabolism hydromineral that the adrenal is vital functions.

Glucocorticoids.
These hormones affect the metabolism of carbohydrates and proteins: they promote, in effect, making the body, carbohydrates, food energy from protein, plastic food, such production is called neo-glycogen; they promotes the synthesis of glycogen in the liver. Steroids were hyperglycaemic action and can run in excess, lead to diabetes (diabetes Steroid). These hormones also act on lipid metabolism: they inhibit lipolysis and alters the distribution of adipose tissue. In addition, corticosteroids act on cells and inhibit the production of antibodies, so they are used to prevent and treat rejection of organ transplants, because of this action, they have an anti-inflammatory.
The essential hormone of this group is cortisol or hydrocortisone which the average production in humans is 15 to 20 mg per 24 hours. The adrenal produces little cortisol, the hormone group and the action of the adrenal glucocorticoid in humans is attributed almost entirely to cortisol.
Glucocorticoids have also, but to a lesser degree of mineralocorticoid properties. This dual action of cortisol is the most active cortical hormones as its single administration is sufficient to keep alive the animal or human adrenalectomized. The discovery of cortisol allowed to practice in humans total adrenalectomy (shown for example in some cancers) and survival to maintain patients whose adrenal glands are destroyed (Addison’s disease).
The hydrocortisone replacement therapy of choice in case of failure of normal hormonal secretion.

The hormone androgen or 17 ketosteroids.
These are hormones whose chemical formula is very close to that of the male genital hormones produced by the testis. The most important of these is the hormone dehydroepiandrosterone DHA The physiological role of adrenal androgens seems low in light of testicular androgens and especially testosterone, which provides the bulk of this function.
The adrenal finally draw a small amount of estrogen (female sex hormones).
These three categories of hormones are inactivated in the liver and then eliminated by the kidneys. The dosages of these various constituents in the urine are of fundamental importance in the study of adrenal disease.
The differentiation of the three areas of the cortex is not only histological but also functional.

• Mineralocorticoids are produced in the zona glomerulosa and this activity is independent of pituitary activity including the secretion of ACTH;
• the glucorticoides are developed in the zone fasciculata and this secretion is under the control of pituitary ACTH;
• androgens are produced in the zona reticularis.

Regulating adrenal
The cortical obey a regulatory complex
The anterior pituitary secretes a hormone stimulating the corticostimuline or AC T. H. (Adreno-cortico-Trophin-Hormon) (or syn ene ACTH) injection which increases the adrenocortical secretion. Secretion KT T. H. is controlled by the hypothalamus: it develops a hormone called CRF, which stimulates the secretion of pituitary ACTH secretion FIU is itself determined by the rate of circulating adrenal hormones. L ‘ AC T .H. KT T. H. acts exclusively on the secretion of metabolic hormones (glucocorticoids).
A control antibody: the latter mechanism occurs only for the secretion of aldosterone in dependence on the renin angiotensin system:
The circulating blood volume and blood pressure: the increase in blood volume inhibits the secretion of aldosterone, its decrease stimulates (via the juxtaglomerular apparatus) is in fact angiotensin (formed by the action of renin developed by the kidney) that directly triggers the secretion of aldosterone. All incentives cause so exciting at first secretion of renin which triggers the secretion of aldosterone. Incentives freinatrices have the opposite effect.
The nervous system is involved in the secretion of aldosterone: any stimulation of the sympathetic nervous system triggers the release of catecholamines. The nerve endings and adrenal medulla. The release of catecholamines causes the secretion of renin (and therefore aldosterone).

Adrenal diseases common
The adrenal insufficiency occurs during the illness of Addison, linked to impairment of cortico-adrenal. The use of etomidate (hypnotic) can also cause adrenal insufficiency.
The cortico-adrenal hyperfunction or hypercortisolism may occur in tumors or hypertrophy of these glands: hypersecretion of aldosterone causes a condition called Conn’s syndrome, hypersecretion of cortisol causes Cushing’s disease, the hypersecretion of sex hormones leads to phenomena of virilization or feminization.
The exploration of the adrenal cortical function is the determination of cortico-steroids or their metabolites in blood and urine.

Hormones
The cathecolamines:
The adrenal medulla secretes two hormones: epinephrine and norepinephrine. These hormones are designated under the broader term of catecholamines.
Secretion under physiological conditions, consists of approximately 90% of adrenaline and noradrenaline 10%.
These two compounds are chemically related but their biological action is similar.
Norepinephrine causes: vasoconstriction except in the coronary vessels; (alpha exclusive positive action)
Adrenaline causes inotropism, bathmotropisme, chronotropic and dromotropic increased and therefore a rise in cardiac output, but also a systemic vasocontriction (action alpha and beta agonists + +) (may be vasodilator in low doses). These two hormones may well lead to hypertension and pressure if it is poorly secreted.
The action on glucose metabolism results in hyperglycemia due to mobilization of liver glycogen, and increased carbohydrate catabolism in all cells but especially muscle cells. Adrenaline is here 4 to 5 times more active than norepinephrine.
The action on 1st lipid metabolism leads to mobilization of fat reserves.
All these metabolic actions involved in the fight against the cold, muscular exertion (increase in muscle performance, delay the onset of fatigue).
Catecholamines cause relaxation of smooth muscle and thereby cause: bronchial dilatation (actiion B2 agonist), decreased gastric peristalsis, and bowel.
The action of catecholamines is comparable to that of the sympathetic. This reflects the fact that norepinephrine is not only a hormone but also the medullary chemical mediator of sympathetic fibers. The sympathetic system and adrenal medulla act so closely connected: the gland is really nice integrated system and can be considered the equivalent of nerve cells postganglionic.

Regulation
The medulla has a low but constant secretion reacts rapidly to emergency situations by increased secretion of catecholamines.
The events that trigger secretion are: hypotension (hemorrhage, shock), muscle power, cold, emotions, pain, hypoglycemia, in short, all circumstances represent an assault on the body or which increase sharply its metabolic needs.
These factors act on the centers of the hypothalamus and medulla stimulation borrows from there ways sympathetic nerve (splanchnic nerve) and is triggered by pre-ganglionic fibers of the sympathetic through their chemical mediator the acetylcholine. The onset of adrenal medullary secretion during attacks carried out by so nervous exclusive and primarily through sympathetic. This reflects a common embryological origin of the sympathetic nervous system and adrenal medulla.
The hyperfunction of the adrenal medulla occurs in cases of pheochromocytoma (tumor). It produces in excess of noradrenaline and adrenaline and results in a paroxysmal hypertension and hyperglycemia.
The exploration of the adrenal medulla secretion, justified if pheochromocytoma is made by measurement of catecholamines and their metabolites in blood and urine.

• The control factor of thyroid stimulating hormone: this factor called T. RH stimulates secretion and release of TSH pituitary.
• The controlling factors of adrenocorticotropic hormone.
• The factors controlling the growth hormone. There are two factors controlling the hormone:


• a stimulating factor, GHRH, which promotes the synthesis and release of the STH;
• factor inhibitor, GHRIH or SRIF or somatostatin, which prevents the release of S. T .H. but also inhibits the secretion by the pancreas to insulin. and glucagon.
• The controlling factors of gonadotrophins. There seems, indeed, one factor for the release of gonadotrophins. This factor called LHRH causes both the regulation of FSH and LH.
• Factors control of prolactin the PRF (prolactin releasing hormone), stimulating, and the PIF (prolactin inhibiting factor), inhibiting.
• The factors controlling the hormone Melanocyte a factor stimulating the MRF, an inhibiting factor, MIF.

The hypothalamus has a role primarily as a regulator dictating via messengers, changes in hormonal glands. His only direct production remains oxytocin and vasopressin, chemically very similar, which are stored and leached by the neurohypophysis.

The Anterior Lobe
The anterior pituitary or adenohypophysis is composed of two kinds of cells: cells chromophil rich granules or acidophilic (40% of anterior pituitary cells) or basophils (10% of cells) and cells chromophobe (50% cells) devoid of granules.
The anterior pituitary secretes many susbtances, hormones or stimulines true:

Growth hormone GH (Grow Hormone)
It is also known as growth hormone. It ensures a harmonious development of the human body and is responsible for the size of the subject. It stimulates growth and therefore in this specific action on the growth plates that hypertrophy significantly under its action. The hypophysectomy leads to arrest of growth in young animals, administration of excessive growth hormone to a normal growth track leads to gigantism.

Growth hormone also has a role in healing.
Finally she has metabolic functions:
* on proteins: it has an anabolic action and synthesis of proteins;
* on carbohydrates: it hyperglycaemic action because it mobilizes the sugar by causing the secretion of pancreatic gIucagon;
* on lipids: it mobilizes fat stores and promote their use for the synthesis of proteins.

The anterior pituitary stimulines
The stimulines are hormones, but that target endocrine cell: they are a sort of intermediary, messenger. They are:
* The cortico-Stimuline ACTH: it stimulates areas fasciculata and reticularis of the adrenal glands and hormone production in these areas (cortisol and androgens), however, there is no action of ACTH on the secretion of ‘aldosterone. ACTH stimulates all stages of the formation of steroids from cholesterol.
* The thyrotropin or thyroid stimulating hormone or TSH: it increases the weight and vascularity of the thyroid gland, it stimulates the follicular cells and all stages of the synthesis of thyroid hormones with increased release of these.
* The GnRH:
* FSH: the female, FSH causes follicle maturation but can trigger ovulation (which requires LH) in males, FSH stimulates spermatogenesis;
* LH: in females, it causes, in synergy with FSH, ovulation, corpus luteum formation and secretion of estrogen and progesterone; males, it stimulates the functioning of Leydig cells and production male hormone, it is noteworthy that the GnRH are identical in both sexes, and that their action is different in men and in women;
* prolactin: it has a dual action on the mammary glands. It has a mammotrope (growth of mammary glands in synergy with estrogen, progesterone 1a and S. T. H.) and an effect lactogen (lactogenesis and maintenance of lactation after childbirth).
* The existence of stimulines explains the atrophy of endocrine glands found in the syndrome of hypopituitarism and after hypophysectomy.

The posterior pituitary (or posterior lobe)
The posterior lobe or posterior pituitary gland is made up of special cells, the pituicytes, surrounded by glia cells.
The post-pituitary hormones are actually synthesized in the hypothalamus and the posterior lobe of the pituitary gland is a single storage location from which they are released into the circulation.
These hormones are two in number: vasopressin (antidiuretic hormone) and oxytocin.

Vasopressin (ADH)
It has two actions:
it causes vasoconstriction;
she has an antidiuretic action: it regulates the renal reabsorption of water it tends to increase, by action at the distal tubule and collecting duct of Bellini It also tends to increase the urinary excretion of chlorine and sodium. Its secretion is dependent upon the osmotic pressure of arterial blood, therefore the water content and electrolytes in it. any increase in osmotic pressure causes the secretion of the hormone and, conversely, any decrease in osmotic pressure inhibiting the secretion of vasopressin. Similarly, any decrease in the circulating blood volume (hypovolemia from dehydration or bleeding) triggers, through reflex from volorécepteurs the atrium, a secretion of ADH alteration of post-pituitary and especially of hypothalamus causes diabetes insipidus, a disease characterized by considerable daily diuresis.
Alcohol, cold inhibit the secretion of ADH.

Oxytocin
It causes contraction of smooth muscle cells including those of the uterus: as such it plays a fundamental role in childbirth. It also occurs in association with the prolactin in the onset of lactation. A synthetic oxytocin used in obstetrics, especially in the post partum, the Syntocinon.

Histologically, the thyroid gland appears as formed by the juxtaposition of many cell blocks which we give the name of thyroid vesicles. Each vesicle is formed and thyroid:
* the center is occupied by a body more or less voluminous gummy substance, yellowish, devoid of any cell. This substance is called colloid;
* each cluster of colloid is surrounded by a single layer of polyhedral epithelial cells. These are cells that develop the colloid to have in reserve in the center of vesicles;
* between thyroid vesicles are very rich capillary network. The appearance of thyroid cells and the amount of colloid contained in the vesicles vary depending on the degree of activity of the gland.


Thyroid Hormones
Thyroid hormones are synthesized and stored within the colloid. It consists of a protein substance whose chemical composition is still incompletely known, thyroglobulin, resulting from the combination of thyroid hormones or their precursors with a globulin.
Thyroid hormones are released from thyroglobulin. These hormones are:
the di-iodo thyronine or T2-, tri-iodo-thyronine or T3, and tetra-iodo-thyronine or thyroxine or T4. These hormones, linked to the thyroglobulin molecule that serves as reserves are released and discharged into the blood where they are attached to transport proteins. Thyroxine alone represents about 75% of circulating thyroid hormones, other hormones, the remaining 25%. These hormones are, in contrast to thyroglobulin, chemically known perfectly. The share taken by the physiological effects of each hormone compounds is uneven: the two most active are the T3 and T4, with a leading role in T3.


The essential fact to know is very rich in iodine of thyroid hormones. Iodine is determined by the avidity with which the gland used for the synthesis of hormones in the laying on thyroglobulin. Also the presence of iodine is indispensable to the activity of the thyroid, any deficiency in iodine determining thyroid hypofunction and goitre. Recent work has uncovered a new thyroid hormone, totally different, thyrocalcitonin. It is a natural protein hormone acting solely on calcium metabolism.
The thyroid gland is endowed with multiple functions that are the consequence of the action it exerts on the metabolism in the cell floor, action we will look first.

Metabolic Actions
The action exerted on the thyroid cell metabolism is the common denominator of all functions of the gland. Generally, thyroid active combustion processes at the cellular level, it is somewhat faster turn the “power station” human. It works like this:
* Energy released by the cell: removal of the gland decreases cell activity and consequently the energy released by the cells, administration of thyroid extracts on the contrary increases the cellular metabolism. Cellular metabolism can be measured easily by basal metabolism: it is significantly lowered (-30% to -45%) after removal of the gland, there are increased cases of thyroid hyperfunction;
* on the metabolism of carbohydrates, lipids, proteins which it accelerates the utilization by the cells of the body, use less if thyroid hypofunction;
* This increase in general metabolism causes an increase in respiratory exchange, an increase of circulating blood volume and cardiac output resulting clinically by palpitations and hot flashes in case of thyroid hyperfunction; hypothroidie causes the opposite phenomena;
* This metabolic action generally plays an important role in regulating body temperature: thyroid fight against cuts in temperature by increasing the production of body heat;
* finally recall that the thyroid plays an important role in the metabolism of iodine. Most of the iodine the body is determined by the gland in the colloid and is used in the development of thyroid hormones.
This action of thyroid stimulation exerted on the cellular activity explains the fundamental role of this gland during the growth period of intense cellular activity. The removal of the thyroid gland in patients undergoing stops the growth of the latter and causes dwarfism thyroid, administration of thyroid extracts corrects problems caused by the removal of the thyroid and this with the results even better than the replacement therapy was begun earlier;
Inadequate thyroid occurring in very young children causes growth retardation in height and weight associated with a considerable lack of intellectual and sexual development (cretinism).

Shares tissue
The thyroid affects the different tissues of the body:
- on the growth plates which prepares the maturation and ossification;
- the female genitalia: the presence of the thyroid is essential for the development of young and female genitalia in particular the onset of puberty;
- on the Annexes to the skin (hair and nails) and teeth and it promotes the growth of hair, nails, the emergence and growth of teeth;
- cell of the higher nervous system: it facilitates the operation of the latter and thereby affects the intellectual development and mental condition. Moreover, the functioning of thyroid disorders cause a stir constantly intellectual and temperamental at Rights: cretinism in children, mental slowing in adults with hypothyroidism, irritability and excitability in hyperthyroidism.

The Thyrocalcitonin
It acts on calcium metabolism: it leads to hypocalcemia primarily by direct action on the system by inhibiting bone resorption. This braking bone catabolism is very important and it significantly reduces the amount of calcium released from the bone. Thyrocalcitonin also determines the hypercalciuria in addition to the above mechanism to achieve hypocalcemia.
The act also thyrocalcitonin on the metabolism of phosphorus, intimately linked to calcium: it leads to hypophosphatemia (decreased blood levels of phosphorus) by the same mechanism and also increasing the urinary excretion of phosphorus.
This hormone has a role antagonistic to that of parathyroid hormone (which is hypercalcemia) in maintaining serum calcium, vital necessity.

Regulating thyroid
Obeys the thyroid hormone secreted by the anterior pituitary gland: thyroid stimulating hormone, or TSH The removal of the pituitary reduced by 90% the activity of the thyroid gland. The pituitary itself is under the control of the hypothalamus, which secretes a hormone which stimulates the secretion of pituitary thyroid stimulating hormone: the hormone is the TRF secretion, and therefore is determined by thyroid hormone levels circulating thyroid: increased secretion in cases of lower rates of circulating thyroid hormones, and vice versa. In human cases of hyperfunctioning thyroid (Graves’ disease) was found abnormal thyroid activator, the LATS, whose activity is very close to that of TSH.
The secretion of thyrocalcitonin is totally independent of pituitary control and depends only on the rate of calcium, increases in the latter leading to increased hormone secretion, and any decrease braking secretion.

exploration and examination
Several tests can be studied in clinical abnormalities of thyroid function:
* The measurement of basal metabolism: increased in hyperthyroidism, decreased in hypothyroidism.
* The determination of blood cholesterol: decreased in hyperthyroidism, increased in hypothyroidism.
* The yarrow reflexogramme: lying in hypothyroidism, hyperthyroidism shortcut.
* The study of thyroid fixation of radioiodine. It allows to draw curves and determination to make maps of the gland. The iodine binding is more rapid than the gland is hyper functioning.
* The blood levels of circulating iodine and thyroid hormones: their rate is even higher than it is a thyroid hyperfunction.