- Title
- Autoimmune hypophysitis: identifying the molecular mechanisms
- Creator
- Crock, Patricia Anne
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2018
- Description
- Research Doctorate - Doctor of Medicine (DMed)
- Description
- My research aim has been to develop a specific and sensitive diagnostic assay for pituitary autoantibodies, to identify the relevant target autoantigens and to understand the molecular mechanisms. This specific body of work spans 25 years and includes 21 publications of which six are reviews. I developed and validated the first immunoblotting assay for the detection of pituitary autoantibodies using autopsy pituitary tissue. One of the first target autoantigens identified, a 49 kDa pituitary cytosolic protein, was purified and found to be enolase. Serum from a patient with peripartum lymphocytic hypophysitis reacted to both alpha‐enolase and gamma‐enolase (neuron specific enolase) in the pituitary and placenta, thus explaining, for the first time, the link between pregnancy and hypophysitis. I identified the first pituitary membrane autoantigens in paediatric patients and we described the first convincing case of hypophysitis in a child with APECED (Autoimmune PolyEndocrinopathy Candidiasis and Ectodermal Dystrophy). Together with many national and international collaborators, we applied the immunoblotting assay across the clinical spectrum from acute to chronic autoimmune pituitary disease and other autoimmune conditions. Several novel clinical associations were found in the largest series of 32 Australian patients with hypophysitis and a number of other pituitary autoantigens were identified by molecular weight. I showed that pituitary autoantibodies are found in patients with other endocrine autoimmune diseases and in up to 20% of pituitary tumour cases. Thus, secondary tumoural hypophysitis cannot be differentiated immunologically, as yet, from primary autoimmune hypophysitis. We found evidence for, and proposed that, the slow progression of post‐partum hypopituitarism in Sheehan’s syndrome may have an autoimmune basis. We showed that some cases of idiopathic hypopituitarism are likely autoimmune and concluded that most patients with empty sella syndrome and normal pituitary function are unlikely to have chronic autoimmune hypophysitis. We demonstrated seroconversion time points for pituitary autoantibodies and their persistence in patients with APECED/APS1 from Finland. In a cohort of Polish patients with isolated ACTH deficiency we found 49 kDa autoantibodies in 20% and a novel 36 kDa pituitary autoantigen that correlated with co‐existent Hashimoto’s thyroiditis, strongly supporting a role for autoimmunity in this syndrome. My focus then changed from immunoblotting to immunoscreening of a pituitary cDNA library to identify further autoantigens and develop in‐vitro transcription translation (ITT) assays. We found a number of novel target autoantigens; CHD8, piccolo and CADPS, the latter two involved in dense core vesicle processing, the mechanism for endocrine peptide hormone secretion. Although none was specific in isolation, 8 of 86 patients with hypophysitis, but none of 90 controls reacted to two or more of these proteins (p=0.0093). We were the first to show the corticotroph‐specific transcription factor, TPIT was a target autoantigen in 10% of hypophysitis patients. APS1 (Autoimmune Polyendocrine Syndrome type 1 – also known as APECED) is a rare, monogenic autoimmune disease and hypopituitarism has been reported in up to 7% of patients. Sera from GH‐deficient APS1 patients identified three major, novel target autoantigens: a tudor domain containing protein 6 (TDRD6), a testis specific protein TSGA10 and endothelin converting enzyme‐2 (ECE‐2). The latter was abundantly expressed in endocrine pancreas as well as in the pituitary and brain. Immunostaining of the pituitary showed that it was localized to GH producing cells. In summary, my work in pituitary autoimmunity started with the development of a new diagnostic assay by immunoblotting and extended to the identification of the first target autoantigens. These autoantigens can be enzymes, transcription factors or proteins involved in dense‐core vesicle transport. However, at present pituitary autoantibodies specific for primary autoimmune lymphocytic hypophysitis cannot be differentiated from those secondary to peri‐ tumoural hypophysitis found in a significant percentage of pituitary tumours and hypothalamic tumours (such as germinomas). Therefore, my focus has now shifted to the new paradigm of diagnosis with epigenetics and biomarkers including miRNA profiling. The ultimate aim is to develop minimally invasive diagnostic testing in paediatric endocrinology.
- Subject
- autoimmune hypophysitis; pituitary autoantibodies; hypopituitarism; empty sella syndrome; TPIT; CHD8; piccolo; CADPS; TSGA10; TDRD6; ECE-2; ITT; pituitary autoantigens; thesis by publication; immunoblotting; immunoscreening; polyglandular endocrine autoimmunity; lymphocytic hypophysitis; Sheehan's syndrome; isolated ACTH deficiency; APS1
- Identifier
- http://hdl.handle.net/1959.13/1395983
- Identifier
- uon:33976
- Rights
- Copyright 2018 Patricia Anne Crock
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 12 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 1 MB | Adobe Acrobat PDF | View Details Download |