THE PITUITARY GLAND 

This is a small, bean-shaped structure that lies at the base of the brain within the confines of the sella turcica. It is connected to the hypothalamus by a "stalk," composed of axons extending from the hypothalamus. The  pituitary is composed of two morphologically and functionally distinct components: the anterior lobe (adenohypophysis) and the posterior lobe (neurohypophysis). The adenohypophysis, in H&E stained sections, shows a colorful collection of cells with basophilic, eosinophilic or poorly staining ("chromophobic") cytoplasm.

Osteoporosis
 
is characterized by increased porosity of the skeleton resulting from reduced bone mass. The disorder may be localized to a certain bone (s), as in disuse osteoporosis of a limb, or generalized involving the entire skeleton. Generalized osteoporosis may be primary, or secondary

Primary generalized osteoporosis
• Postmenopausal
• Senile
Secondary generalized osteoporosis

A. Endocrine disorders
• Hyperparathyroidism
• Hypo or hyperthyroidism
• Others

B. Neoplasia
• Multiple myeloma
• Carcinomatosis 

C. Gastrointestinal disorders
• Malnutrition & malabsorption
• Vit D & C deficiency
• Hepatic insufficiency 

D. Drugs
• Corticosteroids
• Anticoagulants
• Chemotherapy
• Alcohol 

E. Miscellaneous
• osteogenesis imperfecta
• immobilization
• pulmonary disease 

Senile and postmenopausal osteoporosis are the most common forms. In the fourth decade in both sexes, bone resorption begins to overrun bone deposition. Such losses generally occur in areas containing abundant cancelloues bone such as the vertebrae & femoral neck. The postmenopausal state accelerates the rate of loss; that is why females are more susceptible to osteoporosis and its complications. 

Gross features
• Because of bone loss, the bony trabeculae are thinner and more widely separated than usual. This leads to obvious porosity of otherwise spongy cancellous bones

Microscopic features
• There is thinning of the trabeculae and widening of Haversian canals.
• The mineral content of the thinned bone is normal, and thus there is no alteration in the ratio of minerals to protein matrix

Etiology & Pathogenesis

• Osteoporosis involves an imbalance of bone formation, bone resorption, & regulation of osteoclast activation. It occurs when the balance tilts in favor of resorption.
• Osteoclasts (as macrophages) bear receptors (called RANK receptors) that when stimulated activate the nuclear factor (NFκB) transcriptional pathway. RANK ligand synthesized by bone stromal cells and osteoblasts activates RANK. RANK activation converts macrophages into bone-crunching osteoclasts and is therefore a major stimulus for bone resorption.
• Osteoprotegerin (OPG) is a receptor secreted by osteoblasts and stromal cells, which can bind RANK ligand and by doing so makes the ligand unavailable to activate RANK, thus limiting osteoclast bone-resorbing activity.
• Dysregulation of RANK, RANK ligand, and OPG interactions seems to be a major contributor in the pathogenesis of osteoporosis. Such dysregulation can occur for a variety of reasons, including aging and estrogen deficiency.
• Influence of age: with increasing age, osteoblasts synthetic activity of bone matrix progressively diminished in the face of fully active osteoclasts.
• The hypoestrogenic effects: the decline in estrogen levels associated with menopause correlates with an annual decline of as much as 2% of cortical bone and 9% of cancellous bone. The hypoestrogenic effects are attributable in part to augmented cytokine production (especially interleukin-1 and TNF). These translate into increased RANK-RANK ligand activity and diminished OPG.
• Physical activity: reduced physical activity increases bone loss. This effect is obvious in an immobilized limb, but also occurs diffusely with decreased physical activity in older individuals.
• Genetic factors: these influence vitamin D receptors efficiency, calcium uptake, or PTH synthesis and responses.
• Calcium nutritional insufficiency: the majority of adolescent girls (but not boys) have insufficient dietary intake of calcium. As a result, they do not achieve the maximal peak bone mass, and are therefore likely to develop clinically significant osteoporosis at an earlier age.
• Secondary causes of osteoporosis: these include prolonged glucocorticoid therapy (increases bone resorption and reduce bone synthesis.)
The clinical outcome of osteoporosis depends on which bones are involved. Thoracic and lumbar vertebral fractures are extremely common, and produce loss of height and various deformities, including kyphoscoliosis that can compromise respiratory function. Pulmonary embolism and pneumonia are common complications of fractures of the femoral neck, pelvis, or spine. 

Thrombosis

Definition-The formation from constituents of the blood, of a mass within the venous or arterial vasculature of a living animal. Natural defense of the body to acute vascular injury.

Pathologic thrombosis includes deep venous thrombosis (DVT), pulmonary embolism (PE), coronary artery thrombosis leading to myocardial infarct and cerebrovascular thrombosis leading to stroke.

Coagulated blood- clots formed 

Clot – formation of solid mass of blood components formed outside the vascular tree
Thrombosis with resulting embolic phenomena is important cause of morbidity and mortality.

Haemostatic system allows blood to remain in fluid form under normal conditions and causes the development of temporary thrombus at site of vascular injury.

Components of haemostatic system:
1.    Platelets
2.    Vascular endothelium
3.    Procoagulant plasma protein clotting factors
4.    Natural anticoagulants
5.    Fibrinolytic proteins
6.    Antifibrinolytic proteins

Normal haemostasis:
1.    Primary haemostasis-platelet plug formation
2.    Secondary haemostasis-stable plug or thrombus
3.    Natural anticoagulants-confines thrombus site and size to maintain blood flow
4.    Fibrinolysis-degrades fibrin , limits thrombus size and dissolves thrombus once vessel injury is repaired

Changes in any of these factors may result in pathologic thrombosis.

Pathophysiology of thrombosis:
Virchow’s Triad-Thrombosis results from a) decreased blood flow b) vascular endothelial injury and c) alterations in the components of blood.

Vessel wall:
EC (intima), smooth muscle cells (media) and the connective tissue (adventitia).Vascular endothelium is thromboresistant. EC injury leads to TF expression and thrombosis.
Vessel wall has antiplatelet, anticoagulant and fibrinolytic activities which make it thromboresistant.
Antiplatelet activities:
1.    Prostacyclin synthesized by EC in response to thrombin. Inhibits platelet adhesion as well as causes vasodilation
2.    NO regulates vascular tone as well as functioning as inhibitor of platelet adhesion. Constitutive expression as well as induced expression by EC in response to cytokines
3.    Ectozymes which metabolize ADP and ATP to AMP and adenosine. Adenosine inhibits platelet function, ADP is platelet agonist

Anticoagulant activities:
1.    Synthesis of heparin like GAG which inactivate activated clotting factors
2.    Protein C and S and thrombomodulin-Thrombin generated binds to thrombomodulin which activates protein C which then binds to Protein S and this inhibits coagulation by its proteolytic effect on Factors Va and VIIIa
3.    TFPI is synthesized by EC and  regulates TF-VIIa activation of Factor X. Also inhibits vascular cell proliferation

Fibrinolytic activities:
1.    Secretion and synthesis of plasminogen activators TPA in response to thrombin and vasoactive stimulants such as vasopressin and histamine
2.    Synthesis of urokinase in response to inflammatory cytokines
3.    FDP’s generated have antiplatelet and antithrombin activity
4.    Secretion of PAI

Prothrombotic properties of vascular endothelium promote coagulation with appropriates stimuli.

EC exposure to stimuli such as trauma, cytokines, atherogenic stimuli, endotoxins and immune complexes result in increased TF expression, reduced Protein C activation and reduced fibrinolysis so converting an antithrombotic surface to a prothrombotic surface.
Inherited conditions which result in abnormalities of EC derived or regulated proteins will cause thrombosis.

Arterial thrombosis:
1.    Abnormal vessel wall due to atherosclerotic plaque rupture, arterial outflow obstruction, vessel dissection EC injury promote platelet adhesion and activation
2.    Release of contents of platelet granules cause recruitment  and activation of additional platelets
3.    Thromboxane synthesis induces platelet aggregation
4.    Thrombin generation due to presence of PL

Platelets are pathogenetically more important in arterial thrombi thus antiplatelet agents are very important in arterial thrombosis management.

Venous thrombosis:
1.    Vessel wall is usually normal except if there is direct vessel trauma, extrinsic venous compression or damage due to drugs like chemotherapy
2.    Reduction in venous tone is important in pathophysiology

Venous thrombi can be of two types.

A. Phlebo thrombosis 
This is thrombus formation in an uninflammed vein usually due to stasis or changes in coagulability of blood. This occurs mostly in deep calf veins and varicose veins in the legs originating near valve pockets. They may propagate to extend to popliteal ,femoral and iliac-veins. These are a common source of massive emboli ‘Phlegmasia alba dolens’  (painful white leg) is a condition seen in late pregnancy and puerperium.  In this condition, in addition to iliofemoral thrombosis , there is arterial spasm

B Thrombophlebitis:
In this condition venous wall is inflamed and initiates thrombosis. This is more firmly attached to the vessel wall and also there is much less tendency for propagation Hence there is little chance or embolism.

Cardiac Thrombosis
Intra cardiac thrombus formation can be at 3 sites 

•    Valvular: as in endocarditis
•    Atrial : as in atrial fibrilation ('ball valve thrombus") over MacCallum’s patch is Rheumatic Fever.
•    Ventricular mural thrombus  over site of MI

Fate of Thrombus

- Resolution : if small, the thrombus is rapidly covered by endothelial cells. Then it can Resolved by a combination of retraction, phgocytosis , platelet autolysis, and fibrinolysis 
-  Organisation: there is in growth of vascular granulation tissue. This can result in
 a. recanalisation
 b. collagenisation and-scarring
-    Detachment resulting in thromboembolism
 

Autopsy

Autopsy is examination of the dead body to identify the cause of death. This can be for forensic or clinical purposes.

Avitaminoses -  Vitamin deficiencies are more commonly secondary disorders associated with malabsorption conditions and chronic alcoholism.

A. Vitamin A - (retinoids, fat soluble compounds derived from ß-carotene) The best-known effect of deficiency is an inability to see in weak light (night blindness due to decreased rhodopsin).
-> The pathology is also characterized by skin lesions (rash on the extremities with punctate erythematous lesions). In malnourished children, vitamin A supplements reduce the incidence of infections such as measles, even in children without signs of preexisting deficiency.

B. Vitamin D - (1, 25 OH2 D3) Deficiency produces osteomalacia (called rickets in children). Many of the effects of osteomalacia overlap with the more common osteoporosis, but the two disordersare significantly different.
-> The specific alteration in osteomalacia and rickets is a failure of mineralization of the osteoid matrix resulting in decreased appositional bone growth. 

C. Vitamin E - Very rare. Occurs as a secondary disorder in conditions associated with fat maladsorption such as cystic fibrosis, pancreatitis, and cholestasis (bile-flow obstruction).
-> Vitamin E deficiency causes a neurological disorder characterized by sensory loss, ataxia and retinitis pigmentosa due to free radical mediated neuronal damage.

D. Vitamin K - (phylloquinone) Present in most leafy plants and also synthesized by intestinal bacteria. Vitamin K is required for the production of specific clotting factors and a deficiency is characterized by impaired coagulation (elevated clotting times). Although this can occur in newborns that are given breast milk low in vitamin K, the deficiency is almost always secondarily associated with the use of certain anti-coagulants or disorders such as obstructive jaundice, celiac, or pancreatic disease.

 E. Thiamine - (B1) The deficiency is known as beriberi. Thiamine deficiency is characterized by a peripheral neuropathy that affects sensation particularly in the legs (associated with demyelination of peripheral nerves), in more severe cases Korsakoff syndrome (neuropathy characterized by impaired ocular motility, ataxia, and mental confusion) and cardiomyopathy can occur.

F. Nicotinamide (niacin) - The deficiency is known as pellagra. Primary deficiencies are associated with diets that consist primarily of a single low quality protein source (i.e. corn). It results most commonly as a complication of alcoholism.

-> The pathology is characterized by hyperkeratosis and vesiculation of skin, atrophy of the tongue epithelium, and a neuropathy that can affect cortex and peripheral neurons.

- Initial symptoms include a smooth, red tongue, a sore mouth, and ulceration of the inside of the cheeks.

- The skin on the neck, chest, and back of the hands may become brown and scaly. 

- Often there is nausea, vomiting, and diarrhea. There may also be insomnia, depression, confusion, and rapid changes of mood. Long-standing pellagra can result in dementia and death.

G. Vitamin B12 - (cobalamin) Because cobalamin is synthesized by intestinal bacteria and is widely available in many foods, deficiencies are almost always secondary disorders associated with gastric atrophy (and decreased uptake via intrinsic factor), microbial proliferation (AIDS), long-term antacids, chronic alcoholism, idiopathic (age-related).

In addition to anemia, the primary clinical symptoms include a sensory neuropathy (polyneuropathy), sclerosis of the spinal cord and atrophy of some mucous tissues.

H. Vitamin C - (ascorbic acid) The classic deficiency is known as scurvy. The essential pathology involves an inability to produce mature collagen and hence affects connective tissue.

This is characterized by an inability to synthesize osteoid and dentin (and results in decreased wound healing) and a loss of integrity of blood vessel walls.

Oral lesions are only a feature of the advanced form of the disease; early signs include fatigue, dermatitis, and purpura. There can be abnormalities in the growing bones of infants. 

I. Vitamin B6 - (Pyridoxine) A deficiency can lead to peripheral neuropathy, most commonly associated with multivitamin B deficiencies in malnutrition and alcoholism. 

V. Major Minerals - Sodium, potassium, chlorine, and magnesium are required for life but dietary deficiencies do not develop.
A. Iodine - Essential for the synthesis of thyroid hormones, and severe iodine deficiency is  associated with hypothyroidism. The compensatory activity of the thyroid gland causes a  characteristic enlargement called goiter.

B. Calcium - Required for bone mineralization, the RDA for adults is 800 mg/day. Clinical trials have shown that 1000-2000 mg/day can delay the bone loss observed in the elderly and decrease the risk of osteoporosis. See also section IV B.

VI. Trace Elements - At least 10 elements (examples: Co, Mn, Si) are required in minute amounts for normal development and metabolism.

A. Zinc - A deficiency can result from inadequate amounts given during total parenteral nutrition or as a secondary effect of acrodermatitis enteropathica (autosomal recessive trait characterized by alopecia, dermatitis, and diarrhea - the disease responds to administration of zinc).

B. Copper - Deficiencies are rare and primarily associated with malabsorption syndromes and total parenteral nutrition. Copper is required for normal hematopoiesis and bone growth. A deficiency resembles iron deficiency anemia and osteoporosis.

C. Fluoride - Levels in drinking water greater than 1 ppm cause mottling of teeth and in areas with chronic naturally induced fluorosis there is abnormal calcification of ligaments and tendons.

Cytopathologic techniques

Cytopathology is the study of cells from various body sites to determine the cause or nature of disease.

Applications of cytopathology:

1. Screening for the early detection of asymptomatic cancer

2. Diagnosis of symptomatic cancer

3. Surveillance of patients treated for cancer

Cytopathologic methods

There are different cytopathologic methods including:

1. Fine-needle aspiration cytology (FNAC) -In FNAC, cells are obtained by aspirating the diseased organ using a very thin needle under negative pressure.

Superficial organs (e.g. thyroid, breast, lymph nodes, skin and soft tissues) can be easily aspirated.

Deep organs, such as the lung, mediastinum, liver, pancreas, kidney, adrenal gland, and retroperitoneum are aspirated with guidance by fluoroscopy, ultrasound or CT scan.

1. Exfoliative cytology

Refers to the examination of cells that are shed spontaneously into body fluids or secretions. Examples include sputum, cerebrospinal fluid, urine, effusions in body cavities (pleura, pericardium, peritoneum), nipple discharge and vaginal discharge.

1. Abrasive cytology

Refers to methods by which cells are dislodged by various tools from body surfaces (skin, mucous membranes, and serous membranes). E.g. preparation of cervical smears with a spatula or a small brush to detect cancer of the uterine cervix at early stages.