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145. Functional disturbances of the thyroid gland; goitre

A.) Functional disturbances of the thyroid gland

• reduced function (hypothyreosis)– when the thyroid gland is not able to produce

enough hormone for the organism.

• increased function (hyperthyreosis)

HypothyreosisHypothyreosis

• Causes– Thyroid gland aplasia, hypoplasia, atrophia

– Inflammation or tumour of the thyroid gland

– Iodine, vitamin or nucleic acid deficiency

– removal of the thyroid gland

– decreased hormone production due to the damage of the hypophysis → secondary

hypothyreosis

• Occurs in

– neonate, young and adult animals

A A hypothyreosishypothyreosis inin neonateneonate andand youngyoung

animalsanimals• reduced growth of bones

– dwarfing, nanosomia

• hypogonadism

• degeneration of neurons– cretinism

• loss of hair, oedema in the subcutaneous tissue– myxoedema

EnzooticEnzootic myxoedemamyxoedema ofof pigletspiglets ((WasserferkelWasserferkel))

–– apparentlyapparently healthyhealthy sowssows

–– reducedreduced litterlitter

–– myxoedemicmyxoedemic pigletspiglets

–– causedcaused mostlymostly byby iodineiodine deficiencydeficiency ((strumigenstrumigenfactorsfactors))

OccursOccurs alsoalso inin lambslambs

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HypothyreosisHypothyreosis in adult animalsin adult animals

• Mostly in dogs

• Mild clinical symptoms:

– skin: dry, thick, oedemic

– alopecia

– obese, somnolent animals

• Supposed role in the background of acanthosis nigricans and eczemas

• Sheep

– reduced growth of wool

Hyperthyreosis

Increased thyroxin level in the serum

• Basedow- or Graves disease)

• symptoms:– enlarged thyroid gland (goitre)

(struma Basedowiana)– tachycardia– exophthalmia

– hyperactivity, excentricity– histological signs of hyperfunction

in the follicles (columnal epithel)– thyreotoxic crisis

(Schreckbasedow): captured wild animals, panicking people

B., Goitre ((strumastruma))

• Common name for problems of different origin– non-inflammatory, non-neoplastic enlargement of

the thyroid gland

– in mammals and in birds

– may or may not be accompanied with problems of endocrin secretion

– the dysfunction can be reduced or increased function

GoitreGoitre (struma)(struma)

• by the time:– congenital (struma congenita)

– acquired (struma aquisita)

• by location:– the whole organ (struma diffusa)

– partial (struma nodosa)

• by etiology: – hyperplasia of the epithel (struma

parenchymatosa)

– increased amount of product (struma colloides)

StrumaStruma diffusadiffusa parenchymatosaparenchymatosa

• most frequent

• mostly caused by iodine deficiency (hypofunction)

• frequent in neonate and young animals– enlarged firm thyroid gland

– greyish brown hmogenous cut surface

• Histopathology– follicles are hardly recognizable

– columnal epithel

– small, slit-like lumen

– struma diffusa parenchymatosa microfollicularis

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StrumaStruma diffusadiffusa colloidescolloides

• Appearance

– enlarged thyroid gland

– is not firm, cut surface opaque

– enlarged follicles are recognizable

– large amount of (eosinophilic) colloid in the follicles

– flattened epithelial cells

– colloid filled cysts (struma colloides cystica)

GoitreGoitre (struma)(struma)

Secondary changes• after necrosis and fusion of the follicles,

– cysts, pseudocysts: struma cystica

• after compression of the veins– congelation, dilation of capillaries: struma vasculosa s.

teleangiectasia

• after arrodation of blood vessels– haemorrhages (haematomas)

• when connective tissue repleaces the degenerated glandular epithel– struma fibrosa

• within this reparative connective tissue bone formation due to metaplasia– struma ossea

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StrumaStruma nodosanodosa hyperplasticahyperplastica

• nodules in the parenchyma of the thyroid gland

• Hystology:

– resembles to struma parenchymatosa microfollicularis

• mostly in old animals

– horse, dog, cattle

• vicarising hyperplasia

Harmful effects of goitre

• hypothyreosis

• hyperthyreosis

• enlargement, pressure (trachea, oesophagus)

A., Adrenal gland (ganglion suprarenalis)

MedullaRole in the general adaptation syndrome– hormones: adrenalin, noradrenalin

Cortex

• zona arcuata or zona glomerulosa– Mineralocorticoids (aldosterone, deoxicorticosterone)

• zona fasciculata– Glycocorticoids (hydrocortisone, cortisone, corticosterone)

• zona reticularis– androgen hormones

– a sexual steroids

146. Pathological changes in the adrenal gland and the hypophysis and its

consequences

PathologicalPathological changeschanges

• hypofunction

• hyperfunction

• circulatory problems

• regressive changes

• hypertrophy

• inflammation

• tumours

ReducedReduced functionfunction andand consequencesconsequences

• acute hypofunction

– septicaemias → haemorrhages

• calf: E. coli-septicaemia

• chronic hypofunction

– bilateral tuberculosis of the adrenal gland

– toxic effects

Septic haemorrhages

Cortical atrophy of the adrenal glandCortical atrophy of the adrenal gland

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• Chronic hypofunction– brownish colour of skin and mucous membranes

– weakness

– hypotension

– reduced function of gonads

– loss of weight

• in humans: Addison-disease

• in dogs: similar (except hyperpigmentation) after long steroid treatment– reduced ACTH production

– atrophy of adrenal glands

– hypofunction of adrenal glands

Reduced function and consequencesReduced function and consequencesHyperfunctionHyperfunction of the adrenal gland and of the adrenal gland and

its consequencesits consequences

Primary hyperfunction

• hyperadrenocorticism– functional adrenal gland adenoma (paraneoplastic effect)

– diffuse hyperplasia

Cushing-syndrome

• non hypophysis origin hyperadrenocortisolism– fat on face, trunk

– glycosuria

– atrophy of lymphatic organs, gonads

– osteoporosis

– muscle-atrophy

– alopecia

Hyperplasia + control

primary aldosteronism (dog)

• hypernatraemia

• hypokalaemia

• polydypsia

• humans: Conn-syndrome

excess level of sexual steroids

• humans: adrenogenital syndrome

• changes in the secondary sexual character

HyperfunctionHyperfunction of the adrenal gland and of the adrenal gland and

its consequencesits consequencesCirculatory problems of the adrenal Circulatory problems of the adrenal

glandgland

• hyperaemia

• haemorrhages

– per diapedesin

• swine fever, infectious anaemia of horses

• toxicoses, traumas, suffocation

– per rrhexin

• haematomas

• infarcts

• teleangiectasia maculosa

– blood filled follicles

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Regressive changes in the adrenal gland Regressive changes in the adrenal gland

and its consequencesand its consequences

• atrophy

• necrobiotic fatty infiltration

• amyloidosis

• cyst-formation

• calcification

• pigment deposition

Regeneration and hypertrophy of the Regeneration and hypertrophy of the

adrenal glandadrenal gland

hyperplastic nodules in the cortical zone

• in adaptation syndrome

• pea sized

• yellowish white

• well recognizable

• not demarcated

• differential diagnosis

– from the adenoma of the adrenal gland

Hyperplasia nodosa Inflammation of the adrenal gland and Inflammation of the adrenal gland and itsits

consequences (consequences (hypernephritis)

• Acute hypernephritis– inflammatory oedema

• acute diseases

– purulent inflammation (following pyaemia)– necrotic foci

• listeriosis, Aujeszky’s disease, toxoplasmosis (dog)

• chronic hypernephritis– cirrhosis of the adrenal gland (FMD, IEA)

• tuberculosis– tuberculum-formation

Tumours of the adrenal gland and Tumours of the adrenal gland and

consequencesconsequences

primary tumours

• from the cortex

– adenoma (horse, cattle, dog)

– malignant adenoma or carcinoma (cattle)

• from the medulla:

– sympathogonioma, sympathoblastoma,

phaeochromoblastoma,

phaeochromocytoma, ganglionneurinoma

metastases

• rare in animals

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• controlled by the hypothalamus

• anatomic parts

– adenohypophysis

– pars intermedia

– neurohypophysis

B., Hypophysis (pituitary gland or body)

Hormones of the Hormones of the hypophysishypophysis

• adenohypophysis

– gonadotrop hormones (ie. FSH)

– thyreotrop hormone (TSH)

– adrenocorticotrop hormone (ACTH)

– somatotrop hormone (STH)

– melanophor hormone (intermedin)

• neurohypophysis

– adiuretin

– oxytocin

Pathological changes of the Pathological changes of the hypophysishypophysis

and its consequencesand its consequences

• hypofunction of the adenohypophysis

• hyperfunction of the adenohypophysis

• hypofunction of the neurohypophysis

• damage to the hypophysis-hypothalamus

system

• regressive changes of the hypophysis

• inflammations of the hypophysis

• prolipherative changes of the hypophysis

• tumours of the hypophysis

Dysfunction of the adenohypophysis and and

its consequencesits consequences

• hypopituitarism

• hyperpituitarism

Lack or reduced function of the acidophilLack or reduced function of the acidophil--

or or αα--cells of the cells of the adenohypophysisadenohypophysis

Lack of STH

• in young animals:

– nanosomia pituitaria

• in adults:

– cachexia and death (Simmonds-disease)

• Causes:

– atrophy of the adenohypophysis

– necrosis of the frontal lobe of the hypophysis

– inflammation in the adenohypophysis

– or cicatrisation after inflammation

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1 year old German shepherd dog

IncreasedIncreased functionfunction ofof thethe acidophilacidophil-- oror αα--

cellscells ofof thethe adenohypophysisadenohypophysis

• excess level of STH

– ie. hyperplasia, adenoma

• young animals

– gigantismus

• underdeveloped genitals

• not proper hair or fur

• in adults

– acromegalia

• overgrown nose, chin, ears, fingers

• overgrown internal organs

Increased function of the Increased function of the basophilbasophil or or ββ cells cells

of the of the adenohypophysisadenohypophysis

Increased ACTH-production

– mostly in case of basophil cell adenoma

• Cushing-disease!

– characteristics:

• obesity of face, neck, upper torso

• hypertension, hyperglykaemia

• women: hypertrichosis

• men: gynecomastia

• Cushing-syndrome

– The primary hyperfunction of the adrenal gland

– causes secondary β-cell hyperplasia in the hypophysis

– occurs in dogs and horses

Reduced function of the Reduced function of the

neurohypophysisneurohypophysis and its consequencesand its consequences

reduced production of antidiuretichormone

• diabetes insipidus

– consumption of an excess amount of

water (polydypsia) and excretion of low

density urine

– causes: simultaneous damage to the

hypothalamus and the hypophysis

– in dogs and horses

Regressive changes of the Regressive changes of the hypophysishypophysis

and its consequencesand its consequences

• cyst formation

• calcification

• hyalinic degeneration of the stroma

• pigment deposition

– in the adenohypophysis

– ruminants

• atrophy

– horses, dogs

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InflammationInflammation ofof thethe hypophysishypophysis andand itsits

consequencesconsequences

• purulent inflammation

– consequence of haematogenous

metastasis

– or direct contact (purulent meningitis)

• perivascular lymphocytic infiltration inthe neurohypophysisben

– swine fever

– borna disease (sheep)

– infectious anaemia of horses

ProliferativeProliferative changes to the changes to the hypophysishypophysis

and its consequencesand its consequences

• following castration of male animals– acidophil cell proliferation in the

adenohypophysis

– cattle, dog, cat, pig, poultry

• following castration of female animals– has been observed sporadically

• in case of pyometra in dogs– focal hyperplasia of the basophil and the

chromophob cells in the frontal lobe of the hypophysis

Tumours of the Tumours of the hypophysishypophysis and its and its

consequencesconsequencesDogs

– adenomas• frequent in the adenohypophysis

• from the acidophil or basophil cells (or mixed)

– carcinomas• rare

– from remnants of the ducts of the hypophysis• craniopharyngeoma in dogs

• local effect– pressure on the optic nerves

– causes so called „conduction blindness”

• general effect:– acidophil cell tumour:

• Cushing-disease• in young animals: gigantismus

• in adults: acromegalia