Page 810 - Textbook of Pathology, 6th Edition

794 is more common than gigantism. The term ‘acromegaly’ the female, growth of pubic hair and axillary hair. In the
means increased growth of extremities (acro=extremity). female, there is breast growth and onset of menstruation.
There is enlargement of hands and feet, coarseness of facial
features with increase in soft tissues, prominent supraorbital HYPOPITUITARISM
ridges and a more prominent lower jaw which when clenched In hypopituitarism, there is usually deficiency of one or more
results in protrusion of the lower teeth in front of upper teeth of the pituitary hormones affecting either anterior pituitary,
(prognathism). Other features include enlargement of the or posterior pituitary and hypothalamus.
tongue and lips, thickening of the skin and kyphosis.
Sometimes, a few associated features such as TSH excess A. Hypofunction of Anterior Pituitary
resulting in thyrotoxicosis, and gonadotropin insufficiency
causing amenorrhoea in the females and impotence in the Adenohypophyseal hypofunction is invariably due to
male, are found. destruction of the anterior lobe of more than 75% because
the anterior pituitary possesses a large functional reserve.
HYPERPROLACTINAEMIA. Hyperprolactinaemia is the This may result from anterior pituitary lesions or pressure
excessive production of prolactin (PRL), most commonly by and destruction from adjacent lesions. Lesions of the anterior
lactotroph (PRL-secreting) adenoma, also called prolac- pituitary include nonsecretory (chromophobe) adenoma,
tinoma. Occasionally, hyperprolactinaemia results from metastatic carcinoma, craniopharyngioma, trauma,
hypothalamic inhibition of PRL secretion by certain drugs postpartum ischaemic necrosis (Sheehan’s syndrome),
(e.g. chlorpromazine, reserpine and methyl-dopa). In the empty-sella syndrome, and rarely, tuberculosis. Though a
female, hyperprolactinaemia causes amenorrhoea-galactorrhoea number of syndromes associated with deficiency of anterior
syndrome characterised clinically by infertility and expression pituitary hormones have been described, two important
of a drop or two of milk from breast, not related to pregnancy syndromes are panhypopituitarism and dwarfism.
or puerperium. In the male, it may cause impotence or reduced
libido. These features result either from associated inhibition PANHYPOPITUITARISM. The classical clinical condition
of gonadotropin secretion or interference in gonadotropin of major anterior pituitary insufficiency is called
effects. panhypopituitarism. Three most common causes of
panhypopituitarism are: non-secretory (chromophobe)
CUSHING’S SYNDROME. Pituitary-dependent Cushing’s adenoma (discussed later), Sheehan’s syndrome and
syndrome results from ACTH excess. Most frequently, it is Simmond’s disease, and empty-sella syndrome.
caused by corticotroph (ACTH-secreting) adenoma.
SECTION III
Cushing’s syndrome is discussed under diseases of the Sheehan’s syndrome and Simmond’s disease. Pituitary
adrenal gland on page 797. insufficiency occurring due to postpartum pituitary
(Sheehan’s) necrosis is called Sheehan’s syndrome, whereas
B. Hyperfunction of Posterior Pituitary and occurrence of similar process without preceding pregnancy
Hypothalamus as well as its occurrence in males is termed Simmond’s
disease. The main pathogenetic mechanism underlying
Lesions of posterior pituitary and hypothalamus are Sheehan’s necrosis is the enlargement of the pituitary
uncommon. Two of the syndromes associated with hyper- occurring during pregnancy which may be followed by
function of the posterior pituitary and hypothalamus are: hypotensive shock precipitating ischaemic necrosis of the
inappropriate release of ADH and precocious puberty.
pituitary. Other mechanisms hypothesised are: DIC
INAPPROPRIATE RELEASE OF ADH. Inappropriate following delivery, traumatic injury to vessels, and excessive
Systemic Pathology
release of ADH results in its excessive secretion which haemorrhage. Patients with long-standing diabetes mellitus
manifests clinically by passage of concentrated urine due to appear to be at greater risk of developing this complication.
increased reabsorption of water and loss of sodium in the The first clinical manifestation of Sheehan’s syndrome is
urine, consequent hyponatraemia, haemodilution and failure of lactation following delivery which is due to
expansion of intra- and extracellular fluid volume. deficiency of prolactin. Subsequently, other symptoms
Inappropriate release of ADH occurs most often in develop which include loss of axillary and pubic hair,
paraneoplastic syndrome e.g. in oat cell carcinoma of the amenorrhoea, sterility and loss of libido. Concomitant defi-
lung, carcinoma of the pancreas, lymphoma and thymoma. ciency of TSH and ACTH may result in hypothyroidism and
Infrequently, lesions of the hypothalamus such as trauma, adrenocortical insufficiency.
haemorrhage and meningitis may produce ADH
hypersecretion. Rarely, pulmonary diseases such as The morphologic features in the anterior pituitary in
tuberculosis, lung abscess, pneumoconiosis, empyema and Sheehan’s syndrome during early stage are ischaemic
pneumonia may cause overproduction of ADH. necrosis and haemorrhage, while later necrotic tissue is
replaced by fibrous tissue.
PRECOCIOUS PUBERTY. A tumour in the region of
hypothalamus or the pineal gland may result in premature Empty-sella syndrome. Empty-sella syndrome is charac-
release of gonadotropins causing the onset of pubertal terised by the appearance of an empty sella and features of
changes prior to the age of 9 years. The features include panhypopituitarism. Most commonly, it results from
premature development of genitalia both in the male and in herniation of subarachnoid space into the sella turcica due