Hypopituitarism (Simmonds’ disease)

Published on 02/04/2015 by admin

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Last modified 22/04/2025

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143 Hypopituitarism (Simmonds’ disease)

Instruction

Look at this patient.

Salient features

History

• In a male, frequency of shaving, impotence

• In a female, postpartum haemorrhage, amenorrhoea

• History of radiation (e.g. proton-beam radiation): causes hypopituitarism primarily because of its effects on hypothalamic function whereas high-dose radiation can directly affect the pituitary.

Examination

• Patient is pale; the skin is soft

• Paucity of axillary and pubic hair

• Atrophy of breast (in females)

• Examine the BP for postural hypotension

• Check visual fields: bitemporal hemianopia (p. 188) may be present

• Examine the fundus for optic atrophy

• Tell the examiner that you would like to examine the external genitalia for hypogonadism (small testes).

Diagnosis

This patient has pale soft skin and absence of axillary hair with atrophied breasts (lesion) caused by hypopituitarism (functional status) secondary to postpartum necrosis (aetiology).

Questions

Mention a few causes of hypopituitarism

• Iatrogenic: from surgical removal of the pituitary or irradiation

• Chromophobe adenoma (particularly in males)

• Postpartum pituitary necrosis (in females): known as Sheehan syndrome

• Lymphocytic hypophysitis, seen peripartum.

Rare causes:

• Craniopharyngioma

• Metastatic tumours (breast and lung cancers most likely), granulomas (TB, sarcoid, haemochromatosis, histiocytosis X).

How would you assess such a patient?

• FBC for normochromic normocytic anaemia

• Urea and electrolytes for hyponatraemia caused by dilution. Hyperkalaemia does not usually occur because aldosterone production is not affected

• Measurement of pituitary hormones (ACTH, thyroid-stimulating hormone (TSH), luteinizing hormone (LH), growth hormone, prolactin)

• Measurement of target organ secretion: thyroxine (T4), triiodothyronine (T3), plasma free T4, 8 am serum cortisol, testosterone, oestrogen and progesterone

• Pituitary stimulation tests:

• TSH-releasing hormone (TRH) stimulation tests
• Tetracosactrin (synacthen) tests
• Insulin hypoglycaemia test is considered the gold standard used to diagnose growth hormone deficiency in adults, using a diagnostic threshold of 3 mg/l
• LH-releasing hormone (LHRH) tests.

• Skull radiography

• MRI provides the best image of parasellar lesions. The posterior pituitary usually has a high-intensity signal on sagittal MRI that is absent in central diabetes insipidus

• Assessment of visual fields (formal perimetry).

In what order do the hormone secretions generally fail?

In general growth hormone, follicle-stimulating hormone (FSH) and LH secretions become deficient early, followed by TSH and ACTH. Last of all, antidiuretic hormone secretions diminish and fail.

How would you treat such patients?

The mainstay of therapy is lifetime replacement of deficient end-organ deficiencies (thyroid, adrenal and gonads).

Does hypopituitarism affect life expectancy?

Even when hormonal replacement therapy (adrenal, gonadal and thyroid) is carried out in an adequate manner, there is a two-fold risk of death in patients with hypopituitarism (J Clin Endocrinol Metab 1996;81:1169–72). It has been suggested that this is caused by untreated growth hormone deficiency.

Advanced-level questions

What is the Houssay phenomenon?

Houssay showed that diabetes of pancreatectomized dogs improved after hypophysectomy. A diminishing requirement of insulin by diabetics may be a sign of hypopituitarism with diminished secretion of growth hormone and ACTH (and thus corticosteroids). Similarly, diabetes in acromegaly may improve with pituitary surgery or octreotide therapy.

Morris Simmonds of Hamburg described this condition in 1914.

Bernado Alberto Houssay (1889–1971), an Argentinian physiologist in Buenos Aires, was awarded the Nobel Prize for his discovery of the part played by the hormone of the anterior pituitary lobe in the metabolism of sugar. The other half of the Nobel Prize was awarded to Carl and Gerty Cori of St Louis, Missouri, USA, who were awarded the prize for their discovery of the course of the catalytic conversion of glycogen.

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