ACTH SYNTHESIS —
- POMC also contains the sequences for other hormonal peptides, including the melanocyte-stimulating hormones (MSHs) lipotropins (LPHs), and beta-endorphin (beta-END)
- ACTH is synthesized as part of a large precursor (241 amino acids in humans) called proopiomelanocortin (POMC).
Adrenal insufficiency secondary to ACTH deficiency is due to :
- · glucocorticoid withdrawal after long treatment
- · surgical resection of pituitary adenoma
- · pituitary adenomas or other masses due to compression effect
- There is fatigue, weakness, anorexia, nausea, vomiting, hypoglycemia.
- There are no pigmentation changes or mineralocorticoid deficiency which is a feature of primary adrenal failure.
ACTH DEFICIENCY Lab diagnosis:
- low ACTH levels with low cortisol levels.
- On giving ACTH stimulation, there is no cortisol response.
CONTROL OF ACTH SECRETION —
- ACTH secretion is regulated by multiple hormones.
- CRH is probably the most important ACTH secretagogue .
- Beta-END has potent opioid activity in the central nervous system, but its function in peripheral plasma is unknown
- AVP alone is a weak stimulator of ACTH secretion, but it potentiates the action of CRH in vivo and in vitro
Major symptoms and signs of hypothyroidism —
|TSH DEFICIENCY Mechanism||TSH DEFICIENCY Symptoms||TSH DEFICIENCY Signs|
|Slowing ofmetabolic processes||Weight gainMental retardation (infant) Growth failure Fatigue and weakness Dyspnea on exertion Constipation Cold intolerance Cognitive dysfunction||BradycardiaCarotenemia Delayed relaxation of tendon reflexes Slow movement and slow speech|
|Accumulation ofmatrix substances||Dry skinEdema Hoarseness||Coarse skinEnlargement of the tongue Periorbital edema Puffy facies and loss of eyebrows|
|Other||ArthralgiaDecreased hearing Depression Menorrhagia Myalgia and paresthesia Pubertal delay||AscitesDiastolic hypertension Galactorrhea Pleural and pericardial effusions|
- Pituitary hypothyroidism is characterized by low TSH level with low free thyroid hormone.
- Patients with hypothyroidism of hypothalamic origin will have decreased TRH and slightly increased TSH levels.
- TRH 200 IJg IV causes a double increase in TSH levels in half an hour.
- Thyroid replacement therapy.
- Levothyroxine (Synthroid, Levothroid): 1.6 mcg/kg/d; increase by 25 mcg/d every 4–6 weeks until TSH in normal range